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• Organosulfur compounds

Non-sulfur garlic phytochemicals

S-allyl-l-cysteine sulfoxide (alliin), γ-glutamyl-s-allyl-l-cysteine and derivatives, antioxidant activity, anti-inflammatory activity, protection of the cardiovascular system, anticancer activity, antimicrobial activity, cardiovascular disease, supplements, adverse effects, pregnancy and lactation, drug interactions, authors and reviewers, garlic and organosulfur compounds.

• Garlic ( Allium sativum L.) is a particularly rich source of organosulfur compounds, which are currently under investigation for their potential to prevent and treat disease. (More information)
• The two main classes of organosulfur compounds found in whole garlic cloves are L-cysteine sulfoxides and γ-glutamyl-L-cysteine peptides . (More information)
• Crushing or chopping garlic releases an enzyme called alliinase that catalyzes the formation of allicin from S-allyl-L-cysteine sulfoxide (Allin). Allicin rapidly breaks down to form a variety of organosulfur compounds. (More information)
• In vivo studies indicate that allicin-derived organosulfur compounds may be poorly bioavailable , whereas water-soluble derivatives of γ-glutamyl-L-cysteine peptides have been detected in plasma , liver, and kidney following oral consumption. (More information)
• Several different types of garlic supplements are available commercially, and each type provides a different profile of organosulfur compounds depending on how it was processed. (More information)
• Numerous preclinical studies reported that organosulfur compounds from garlic could exert antioxidant , anti-inflammatory, antimicrobial , anticancer, and cardioprotective activities in various experimental settings. (More information)
• The results of randomized controlled trials suggested that garlic supplementation modestly improves serum lipid profiles in individuals with elevated serum cholesterol and reduces blood pressure in hypertensive subjects, at least in the short term. It is not known whether garlic supplementation can help prevent cardiovascular disease .  (More information)
• Current evidence from observational studies does not support an association between high intakes of garlic and prevention of cancer , including gastric and colorectal cancer . It is not known whether garlic-derived organosulfur compounds may be effective in preventing or treating human cancers. (More information)

Introduction

Garlic ( Allium sativum L.) has been used for culinary and medicinal purposes in many cultures for centuries (1) . Garlic is a particularly rich source of organosulfur compounds, which are thought to be responsible for its flavor and aroma, as well as its potential health benefits (2) . Consumer interest in the health benefits of garlic is strong enough to place it among the best-selling herbal supplements in the United States (3) . Scientists are interested in the potential for organosulfur compounds derived from garlic to prevent and treat chronic diseases , such as cancer and cardiovascular disease (4) .

Organosulfur compounds from garlic

Two classes of organosulfur compounds are found in whole garlic cloves: L-cysteine sulfoxides and γ-glutamyl-L-cysteine peptides.

L-Cysteine sulfoxides

S-allyl-L-cysteine sulfoxide (alliin) accounts for approximately 80% of cysteine sulfoxides in garlic ( Figure 1 ) (5) . When raw garlic cloves are crushed, chopped, or chewed, an enzyme known as alliinase is released. Alliinase catalyzes the formation of sulfenic acids from L-cysteine sulfoxides ( Figure 2 ). Sulfenic acids spontaneously react with each other to form unstable compounds called thiosulfinates. In the case of alliin, the resulting sulfenic acids react with each other to form a thiosulfinate known as allicin (half-life in crushed garlic at 23°C is 2.5 days). The formation of thiosulfinates is very rapid and has been found to be complete within 10 to 60 seconds of crushing garlic. Allicin breaks down in vitro to form a variety of fat-soluble organosulfur compounds ( Figure 2 ), including diallyl trisulfide (DATS), diallyl disulfide (DADS), and diallyl sulfide (DAS), or in the presence of oil or organic solvents, ajoene and vinyldithiins (6) . In vivo , allicin can react with glutathione and L-cysteine to produce S-allylmercaptoglutathione (SAMG) and S-allylmercaptocysteine (SAMC), respectively ( Figure 2 ) (4) .

γ-Glutamyl-L-cysteine peptides                                

Crushing garlic does not change its γ-glutamyl-L-cysteine peptide content. γ-Glutamyl-L-cysteine peptides include an array of water-soluble dipeptides, including γ-glutamyl-S-allyl-L-cysteine, γ-glutamylmethylcysteine, and γ-glutamylpropylcysteine (see Figure 1 ). Water-soluble organosulfur compounds, such as S-allylcysteine and SAMC ( Figure 3 ), are formed from γ-glutamyl-S-allyl-L-cysteine during long-term incubation of crushed garlic in aqueous solutions, as in the manufacture of aged garlic extracts (see Sources ). 

Although little is known about their bioavailability and biological activities, non-sulfur garlic phytochemicals, including flavonoids , steroid saponins, organoselenium compounds, and allixin, likely work in synergy with organosulfur compounds (6) .

[Figure 1 - Click to Enlarge]

[Figure 2 - Click to Enlarge]

[Figure 3 - Click to Enlarge]

Metabolism and Bioavailability

In studies conducted in rodents, orally administrated alliin was found to be absorbed intact and to reach plasma and liver without being converted to allicin. There are no thiosulfinates (like allicin) in intact garlic cloves, and none can be generated in the stomach because alliinase would be irreversibly inhibited under acidic conditions (6) .

Allicin and derivatives

The absorption and metabolism of allicin and allicin-derived compounds (see Figure 2 ) are only partially understood (7) . In humans, no allicin has been detected in the serum or urine up to 24 hours after the ingestion of 25 g of raw garlic containing a significant amount of allicin (8) . Before ingestion in garlic preparations and after ingestion in the stomach, allicin likely breaks down to release a number of volatile compounds, including DAS and DADS. These organosulfur compounds are metabolized to allyl mercaptan, allyl methyl sulfide, and allyl methyl disulfide, which have been detected in human breath after garlic consumption (9-11) . Although a number of biological activities have been attributed to various allicin-derived compounds, it is not yet clear which of these compounds or metabolites actually reaches target tissues (5) . Allyl methyl sulfide — but not allyl mercaptan — has been detected in the urine within four hours of garlic ingestion, suggesting that this compound is absorbed into the circulation and rapidly excreted (11) . Other allicin-derived compounds, including diallyl sulfides, ajoenes, and vinyldithiins, have not been detected in human blood, urine, or stool, even after the consumption of up to 25 g of fresh garlic or 60 mg of pure allicin (5) . These findings suggest that, if they are absorbed, allicin and allicin-derived compounds are rapidly metabolized.

γ-Glutamyl-S-allyl-L-cysteine is thought to be absorbed intact and hydrolyzed to S-allyl-L-cysteine (SAC) and trans -S-1-propenyl-L-cysteine (see Figure 3 ), since metabolites of these compounds have been measured in human urine after garlic consumption (12, 13) . The consumption of aged garlic extract, a commercial garlic preparation that contains SAC, has been found to increase plasma SAC concentrations in humans (14-16) . SAC has been detected in plasma, liver, and kidney of SAC-fed animals (17) . Water-soluble organosulfur compounds like SAC and its metabolite, N-acetyl-S-allyl-L-cysteine, may be used as reliable markers of compliance in clinical trials involving garlic intake (6 , 18) .

Biological Activities

Glutathione.

Low cellular concentrations of glutathione , a major intracellular antioxidant , and/or overproduction of reactive oxygen species (ROS) can lead to oxidative stress -induced damage to biological macromolecules and contribute to the development and progression of pathological conditions. In endothelial cells (that line the inner wall of blood vessels), garlic-derived allicin lowered ROS production and increased the concentration of glutathione (19) . Oral administration of allicin to mice lowered ROS production and prevented ROS-induced cardiac hypertrophy by inhibiting pro-inflammatory pathways like mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/glycogen synthase kinase 3β (GSK3β) signaling pathways (20) . It is thought that, upon crossing cell membranes , allicin interacts with glutathione and forms SAMG (see Figure 2 ), which could prolong the antioxidant activity of allicin (19) .

Nrf2-dependent antioxidant pathway

Allicin was also found to upregulate the expression of glutamate-cysteine ligase (GCL), the rate-limiting enzyme in glutathione synthesis , and other Phase II detoxifying/ antioxidant enzymes, likely via the activation of the nuclear factor E2-related factor 2 (Nrf2)-dependent pathway (19) . Briefly, Nrf2 is a transcription factor that is bound to the protein Kelch-like ECH-associated protein 1 (Keap1) in the cytosol . Keap1 responds to oxidative stress signals by freeing Nrf2. Upon release, Nrf2 translocates to the nucleus and binds to the antioxidant response element (ARE) located in the promoter of genes coding for antioxidant/detoxifying enzymes and scavengers . Nrf2/ARE-dependent genes code for numerous mediators of the antioxidant response, including GCL, glutathione S-transferases (GSTs), thioredoxin, NAD(P)H quinone oxidoreductase 1 (NQO-1), and heme oxygenase 1 (HO-1) (21) . Like allicin, oil-soluble organosulfides, DADS and DATS (see Figure 2 ), have been shown to stimulate Nrf2-dependent antioxidant pathway (4) . For example, antioxidant and cytoprotective effects of DADS against acute ethanol-induced liver damage in mice were associated with the ability to trigger Nrf2-dependent HO-1 activation (22) . DATS protected cardiac cells in vitro and in experimental diabetic rats from high glucose -induced oxidative stress and apoptosis by inducing PI3K/Akt-dependent Nrf2 antioxidant signaling (23) .

Aged garlic extract have also been shown to increase expression of antioxidant enzymes via the Nrf2/ARE pathway (24) . SAC, a major organosulfur compound in aged garlic extract, prevented renal damage caused by ROS in cisplatin-treated rats, by limiting cisplatin-induced reduction of glutathione level, Nrf2 expression, and activity of several antioxidant enzymes (catalase, glutathione reductase, glutathione peroxidase) (25) . SAC also protected neurons from oxidative damage and apoptosis in wild-type mice but not in mice without a functional Nrf2 signaling pathway (26) .

Nitric oxide (NO) signaling cascade

The generation of nitric oxide (NO) catalyzed by endothelial nitric oxide synthase (eNOS) plays a critical role in protecting the vascular endothelium from oxidative and inflammatory insults (27) . ROS -induced NO inactivation can impair vascular endothelial function, contributing to various pathologies like atherosclerosis , hypertension , cardiovascular disease , and central nervous system disorders (27, 28) . Interestingly, ingestion of 2 g of fresh garlic was found to increase NO plasma concentrations within two to four hours in healthy volunteers (29) . DADS and DATS protected eNOS activity and NO bioavailability in cultured endothelial cells challenged with oxidized low-density lipoprotein ( LDL ) (30) . In a model of traumatic brain injury in rats, allicin attenuated brain edema , neurological deficits, and apoptotic neuronal death, and exhibited antioxidant and anti-inflammatory effects, partly by increasing Akt-mediated eNOS activation (31) . Aged garlic extract and SAC were also found to stimulate NO production in different experimental settings (32) . In a model of erectile dysfunction in diabetic rats, SAC restored electrically-induced penile erection by stimulating eNOS activity and inhibiting the expression of NADPH oxidase (Nox) responsible for ROS overproduction (33) .

Garlic-derived organosulfur compounds have been found to inhibit mediators of the inflammatory response, including cytokines , chemokines, adhesion molecules, and enzymes like cyclooxygenase (COX), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS) (34-36) . Nuclear factor-kappa B (NF-κB) is a transcription factor that binds DNA and induces the transcription of the COX-2 gene , other pro-inflammatory genes, as well as genes involved in cell proliferation , adhesion, survival, and differentiation . The anti-inflammatory effects of organosulfur compounds result from their ability to counteract the activation of pro-inflammatory pathways — like NF-κB-, MAPK-, and PI3K/Akt-dependent signaling pathways — by pro-inflammatory stimuli (4) . DATS inhibited bacterial lipopolysaccharide (LPS)-induced macrophage activation by limiting LPS binding to toll-like receptor 4 (TLR4) and blocking the upregulation of TLR4 and TLR4-associated molecule MyoD88 expression (37) . DATS also inhibited LPS-induced NF-κB-dependent expression of COX-2, iNOS, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) (37) . In a mouse model of inflammation, the decrease of LPS-induced paw edema by DATS was associated with reduced serum concentrations of the pro-inflammatory cytokines, TNF-α, IL-6, and monocyte chemotactic protein-1 (MCP-1) (36) .

Inhibition of cholesterol synthesis

Garlic and garlic-derived organosulfur compounds have been found to decrease the synthesis of cholesterol by hepatocytes (38) . Several garlic-derived organosulfur compounds, including S-allylcysteine and ajoene, have been found to inhibit 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMG-CoA reductase), a critical enzyme in the cholesterol biosynthesis pathway (39, 40) . Garlic-derived compounds may also inhibit other enzymes in this pathway, including sterol 4α-methyl oxidase (41) .

Inhibition of platelet aggregation

An increase in the ability of platelets to aggregate has been linked to the narrowing of blood vessels and the occurrence of acute thrombotic events. A variety of garlic-derived organosulfur compounds have been found to inhibit platelet aggregation in the test tube (42-44) . Aged garlic extract was found to inhibit chemically stimulated platelet aggregation by downregulating the fibrinogen binding activity of glycoprotein IIb/IIIa fibrinogen receptor found on platelets (45, 46) and/or by preventing intraplatelet calcium mobilization (42) .

Inhibition of vascular smooth muscle cell (VSMC) proliferation

The proliferation and migration of normally quiescent VSMCs are central features of vascular diseases, including atherosclerosis and coronary restenosis (when treated arteries become blocked again) (47) . Although the significance of these findings for human cardiovascular disease is not yet clear, limited cell culture research suggested that organosulfur compounds from garlic could inhibit the proliferation and migration of VSMCs (39 , 48, 49) .

Inhibition of vascular cell adhesion molecules

An elevation of oxidized low-density lipoprotein ( LDL ) concentration in plasma has been involved in the pathogenesis of atherosclerosis . Oxidized LDL may stimulate the recruitment of inflammatory white blood cells from the blood to the arterial wall by inducing the expression of vascular cell adhesion molecules. DADS and DATS inhibited the expression of adhesion molecules, E-selectin and vascular cell adhesion molecule-1 (VCAM-1), on endothelial cell surface by reversing oxidized LDL-induced inhibition of PI3K/Akt and cAMP responsive element binding protein (CREB) signaling pathways (50) .

Hydrogen sulfide-mediated vasodilatory activity

The preservation of normal arterial function plays an important role in cardiovascular disease prevention. Hydrogen sulfide (H 2 S), a gaseous signaling molecule produced by some cells within the body, acts as a vasodilator (relaxes blood vessels) and thus may have cardioprotective properties (51, 52) . H 2 S production may be involved in vascular smooth muscle cell relaxation through regulating the opening/closing of potassium channels and/or enhancing NO-dependent signaling pathway (reviewed in 53 ). A study found that garlic-derived compounds are converted to hydrogen sulfide by red blood cells in vitro (54) . However, human consumption of a high dose of raw garlic does not increase breath hydrogen sulfide levels, suggesting that significant metabolism of garlic compounds to hydrogen sulfide does not occur in vivo (11) .

Note that the potential benefits of garlic consumption/ supplementation on cardiovascular health may also be attributed to antioxidant and anti-inflammatory activities described above.

Effects on carcinogen metabolism

Inhibition of metabolic activation of carcinogens : Some chemical carcinogens do not become active carcinogens until they have been metabolized by Phase I biotransformation enzymes , such as those belonging to the cytochrome P450 (CYP) family. Inhibition of specific CYP enzymes involved in carcinogen activation inhibits the development of cancer in some animal models (55) . In particular, DAS and its metabolites have been found to inhibit CYP2E1 activity in vitro (56, 57) and when administered orally at high doses to animals (58, 59) . Oral administration of garlic oil and DAS to humans has also resulted in evidence of decreased CYP2E1 activity (60-62) .

Induction of Phase II detoxifying enzymes : Reactions catalyzed by phase II detoxifying enzymes generally promote the elimination of drugs, toxins, and carcinogens from the body. Consequently, increasing the activity of phase II enzymes, such as glutathione S-transferases (GSTs) and NQO-1, may help prevent cancer by enhancing the elimination of potential carcinogens (see the Nrf2-dependent antioxidant pathway ) (63) . In animal studies, oral administration of garlic preparations and organosulfur compounds was found to increase the expression and activity of phase II enzymes in a variety of tissues (64-66) . For example, DADS protected rodent liver against carbon tetrachloride (CCl 4 ; an environmental pollutant)-induced lipid peroxidation and cell necrosis by blocking CYP2E1-mediated CCL 4 metabolic activation and by upregulating Nrf2 downstream genes for NQO-1, HO-1, GCL, GST, and superoxide dismutase (SOD1) (67, 68) .

Induction of cell cycle arrest

In normal cells, the cell cycle is tightly regulated to ensure faithful DNA replication and chromosomal segregation prior to cell division. When defects occur during DNA replication or chromosomal segregation and in case of DNA damage, the cell cycle can be transiently arrested at check points to allow for repair. Apoptosis is triggered when repair fails. Defective check points and evasion of apoptosis allow the unregulated division of cancer cells (69) . Organosulfur compounds, including allicin, DAS, DADS, DATS, ajoene, and SAMC, have been found to induce cell cycle arrest when added to cancer cells in cell culture experiments (reviewed in 4 , 70 ). DATS reduced the incidence of poorly differentiated prostate tumors and limited the number of metastatic lesions in the lungs of mice genetically modified to develop prostate adenocarcinomas (71) . DATS was shown to inhibit cancer cell proliferation , as well as neuroendocrine differentiation — a hallmark of prostate cancer malignancy — but had no effect on apoptosis and markers of invasion (71) . In a rat model of chemically induced colon cancer, inhibition of cell proliferation by aged garlic extract was associated with a reduction in the incidence of precancerous lesions and dysplastic adenomas, but not of adenocarcinomas (72) .

Induction of apoptosis

Apoptosis is a physiological process of programmed death of cells that are genetically damaged or no longer necessary. Precancerous and cancerous cells are resistant to signals that induce apoptosis (73) . Garlic-derived organosulfur compounds, including allicin, ajoene, DAS, DADS, DATS, and SAMC, have been found to induce apoptosis when added to various cancer cell lines grown in culture (reviewed in 4 , 70 ). Oral administration of aqueous garlic extract and S-allylcysteine has been reported to enhance apoptosis in an animal model of oral cancer (74, 75) . Garlic oil reduced the incidence of N-nitrosodiethylamine-induced liver nodules by preventing oxidative damage to lipids and DNA and by promoting apoptosis (76) . Garlic oil upregulated the activity of various antioxidant enzymes and expression of pro-apoptotic effectors like Bax and Caspase-3 and downregulated the expression of the anti-apoptotic genes β-arrestin-2, Bcl-2, and Bcl-X (76) .

Inhibition of angiogenesis

To fuel their rapid growth, invasive tumors must develop new blood vessels by a process known as angiogenesis . Anti-angiogenic properties of several organosulfur compounds, including alliin, DATS, and ajoene, have been observed in in vitro or ex vivo experiments (70) . In human breast cancer cells, DADS inhibited TNF-α-induced release of MCP-1, a chemokine that promotes tissue remodeling, angiogenesis, and metastasis (77) . Aged garlic extract was also found to suppress in vitro angiogenesis by inhibiting endothelial cell proliferation , loss of adhesion, motility, and tube formation (78) .

Garlic extracts have been found to have antibacterial and antifungal properties (79, 80) . Thiosulfinates, particularly allicin, are thought to play an important role in the antimicrobial activity of garlic (80-82) . Allicin-derived compounds, including DATS and ajoene, also have some antimicrobial activity in vitro (5) . To date, randomized controlled trials using oral garlic preparations have not provided strong evidence for such activity in humans (83-85) . A small randomized controlled trial found that application of 1% ajoene cream to the skin twice daily was as effective in treating tinea pedis (fungal skin infection known as athlete’s foot) as 1% terbinafine (Lamisil) cream (86) . In another preliminary randomized controlled trial, circulating immune innate cells (γδT- lymphocytes and natural killer (NK) cells ), isolated from healthy adults supplemented with aged garlic extract, proliferated better in ex vivo culture than those from volunteers who consumed a placebo , suggesting a greater pathogen -fighting ability. The number of self-reported illnesses was similar between groups after 90 days of aged garlic extract or placebo supplementation, but aged garlic extract significantly reduced the severity of self-reported cold or flu symptoms (87) .

Disease Prevention

Interest in garlic and its potential to prevent cardiovascular disease began with observations that people living near the Mediterranean basin had lower mortality from cardiovascular disease (88) . Garlic is a common ingredient in Mediterranean cuisine, but a number of characteristics of the "Mediterranean diet" have been proposed to explain its cardioprotective effects (89) . Although few observational studies have examined associations between garlic consumption and cardiovascular disease risk , numerous intervention trials have explored the effects of garlic supplementation on cardiovascular disease risk factors.

Platelet aggregation

Platelet aggregation is one of the first steps in the formation of blood clots that can occlude coronary or cerebral arteries, leading to myocardial infarction or ischemic stroke , respectively. Evidence that garlic inhibits platelet aggregation is based mainly on in vitro experiments and a small number of ex vivo assays. Of 10 randomized controlled trials that tested the antithrombotic effect of garlic preparation, four reported a modest but significant decrease in ex vivo platelet aggregation with garlic supplementation compared to placebo (reviewed in 90 ). Because garlic oil extract in particular may have antithrombotic activity, a small randomized controlled trial in 12 healthy adults was conducted to test the acute effect of one large dose of garlic oil (extracted from 9.9 g of fresh garlic) on ex vivo platelet aggregation (91) . The garlic oil extract had a mild effect on adrenaline-induced platelet aggregation (12% reduction) but had no effect on adenosine diphosphate (ADP)- or collagen -induced aggregation measured four hours post-consumption. Another study in 14 healthy volunteers showed that aged garlic extract dose-dependently inhibited ADP-stimulated platelet aggregation by downregulating the fibrinogen binding activity of glycoprotein IIb/IIIa fibrinogen receptor found on platelets (46) .

Serum lipid profiles

A recent systematic review of randomized controlled trials examining the effect of supplementation with various garlic preparations on serum lipid profiles in individuals with elevated and normal serum cholesterol levels reported mixed results (92) . The most recent and comprehensive meta-analysis compared the results from 39 randomized controlled trials published between 1955 and 2011 that tested the effect of garlic preparations on serum lipid concentrations (93) . These 39 trials studied 2,298 adult participants (mean age, 49.5 years), administered garlic-only preparations, used a true placebo , and lasted for at least two weeks. The majority of included trials recruited subjects with elevated total cholesterol at baseline (>200 mg/dL [>5.2 mmol/L], 29 trials) and lasted more than eight weeks (30 trials). The authors found that garlic preparations significantly lowered total cholesterol and low-density lipoprotein ( LDL )-cholesterol compared to placebo. High-density lipoprotein ( HDL )-cholesterol concentrations were mildly increased and triglyceride concentrations were not affected by garlic supplementation. All administered garlic preparations (garlic powder, aged garlic extract, garlic oil, and fresh garlic) were well tolerated and associated with only minor side effects (garlic odor and mild gastrointestinal discomfort) (93) .

Although garlic supplementation for a minimum of two months may lower total- and LDL-cholesterol concentrations in individuals with elevated total cholesterol, the benefits may not last beyond the short term (90, 92) . Whether garlic possesses long-lasting lipid-lowering effects remain questionable and future investigations may focus on ways to maximize potential benefits of garlic preparations on serum lipids. 

Atherosclerosis

Very few studies have attempted to assess the effect of garlic supplementation on the progression of atherosclerosis in humans. One early study in Germany used ultrasound imaging to assess the effect of 900 mg/day of dehydrated garlic on the progression of atherosclerotic plaque in the carotid and femoral arteries (94) . After four years, the increase in plaque volume was significantly greater in women taking the placebo (+53.1%) than in women taking the garlic supplement (-4.6%), while no significant difference in plaque volume was found between garlic (+1.1%) and placebo (+5.5%) in men (94, 95) . In a smaller pilot study , investigators measured coronary artery calcium using electron-beam computed tomography to assess the effect of supplementation with aged garlic extract on the progression of atherosclerosis in 19 adults already taking HMG-CoA reductase inhibitors (lipid-lowering drugs also known as statins) (18) . After one year, increases in coronary artery calcium score were significantly lower in those taking aged garlic extract than in those taking a placebo. Nevertheless, although coronary calcium scores may have a predictive value regarding future cardiac events in asymptomatic subjects, it may not be a reliable marker of plaque burden in symptomatic patients (96, 97) . In a recent double-blind , controlled study, the extent of coronary atherosclerosis was assessed with cardiac computed tomography angiography in 72 individuals (55 at study completion) at high risk of coronary heart disease randomized to receive either 2,400 mg of aged garlic extract or placebo for 52 weeks (98) . The result suggested a significant decrease in the extent of coronary plaques with low-attenuation area (a type of vulnerable plaques prone to rupture) (99, 100) with aged garlic extract compared to placebo, but no differences in total plaque volume and proportions of non-calcified plaques and dense calcium were found between treatment and placebo groups (98) .

Hypertension

Most systematic reviews and/or meta-analyses of randomized controlled trials to date have provided mixed results regarding the potential blood pressure-lowering effect of garlic, possibly because most of these trials enrolled both normotensive and hypertensive subjects (90 , 101-105) .

A systematic review and meta-analysis by Xiong et al. (106) included seven randomized , placebo -controlled trials that exclusively enrolled individuals with high blood pressure, i.e., with systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg. Five out of seven trials identified in this systematic review reported statistically significant reductions in SBP and DBP with several garlic preparations (dried garlic homogenate, garlic powder, and aged garlic extract) (106) . Another recent meta-analysis included nine randomized controlled trials in 482 hypertensive individuals who were given garlic powder (six studies), garlic homogenate (one study), aged garlic extract (two studies), or placebo for 8 to 26 weeks (107) . Garlic preparations were found to significantly reduce SBP by a mean of 9.1 mm Hg and DBP by a mean of 3.8 mm Hg compared to placebo. The most recent meta-analysis found that garlic preparations reduced SBP by a mean 8.7 mm Hg (10 trials, 440 subjects) and DBP by 6.1 mm Hg (8 trials, 257 subjects) (102) . Such reductions in blood pressure seem comparable to those reported with currently used classes of blood pressure-lowering medications (average reduction, -9.1 mm Hg for SBP and -5.5 mm Hg for DBP) (108) . The effect of blood pressure reduction from such medications at standard dose has been estimated to lower the risk of coronary heart disease events by about one-quarter and the risk of stroke by about one-third (108) . Nonetheless, evidence showing that garlic supplements may reduce the risk of cardiovascular morbidity and mortality is still lacking (109) .

In a recent 12-week, randomized, placebo-controlled trial in untreated hypertensive subjects, daily intake of aged garlic extract (1.2 g of which contained 1.2 mg of S-allyl-L-cysteine [SAC]) was shown to significantly lower SBP by 11 mm Hg and DBP by 6 mm Hg on average in 50%-60% of participants, but reductions in blood pressure were not reported in 40%-50% of participants compared to placebo (110) . Whether interindividual differences in nutritional status and genetic polymorphisms can explain differences in blood pressure response to garlic treatment need to be explored in future studies (53 , 110) .

Overall, short-term garlic supplementation appears to effectively reduce blood pressure with minimal side effects in hypertensive patients.

The results of randomized controlled trials have suggested that garlic supplementation modestly improves serum lipid profiles in individuals with elevated serum cholesterol and reduces blood pressure in hypertensive subjects. It is not yet clear whether garlic supplementation can reduce atherosclerosis or prevent cardiovascular events, such as myocardial infarction or stroke .

Gastric cancer

A recent meta-analysis of 17 studies (mostly case-control studies ) reported an inverse association between high versus low garlic consumption and the risk of gastric cancer (111) . Nevertheless, this conclusion is hindered by a number of limitations, especially related to the retrospective design of most studies included in the analysis, as well as great variations in the amount and duration of garlic intakes. In a 2009 review of the literature, Kim et al. (112) identified 20 human studies that examined garlic intake in relation to gastric cancer risk: three intervention studies , one case-cohort study, 13 case-control studies, and three cross-sectional / ecologic studies. Using the Food and Drug Administration (FDA)’s evidence-based criteria for the scientific evaluation of health claims (113) , the authors excluded 16 studies for methodological flaws; only four studies (two case-control (114, 115) , one case-cohort (116) , and one intervention (85) ) received moderate-to-high quality ratings (112) . Among these four studies, garlic intake during adolescence or 20 years prior to the interview was not found to be associated with the risk of gastric cancer in one of the case-control studies in Sweden (338 gastric cancer patients and 669 control subjects) (114) . Another case-control study in Korea failed to show an association between past garlic consumption and gastric cancer in 136 people diagnosed with gastric cancer and 136 cancer-free subjects (115) . In addition, a prospective case-cohort study in the Netherlands found no association between the use of garlic supplements (unknown composition) and gastric cancer risk (116) . Finally, a randomized , double-blind , placebo -controlled intervention study in 3,365 subjects from the Shandong province of China found that supplementation with aged garlic extract and steam-distilled garlic oil for 7.3 years did not reduce the prevalence of precancerous gastric lesions or the incidence of gastric cancer (85) . An updated analysis of the data collected 7.3 years after garlic supplementation ended provided further confirmation for a lack of significant reduction in gastric cancer incidence or mortality with supplemental garlic (117) .

Helicobacter pylori ( H. pylori) infection and gastric cancer : Infection with some strains of H. pylori bacteria markedly increases the risk of gastric cancer . Although garlic preparations and organosulfur compounds could inhibit the growth of H. pylori in the laboratory (118, 119) , there is little evidence to suggest that high garlic intakes or garlic supplementation may help prevent or eradicate H. pylori infection in humans (120) . Higher intakes of garlic were not associated with a significantly lower prevalence of H. pylori infection in China or Turkey (121, 122) . Moreover, clinical trials using garlic cloves (123) , aged garlic extract (84) , steam-distilled garlic oil (84 , 124) , garlic oil macerate (125) , or garlic powder (126) have not found garlic supplementation to be effective in eradicating H. pylori infection in humans.

Colorectal cancer

A 2014 meta-analysis of prospective cohort studies in 335,923 subjects (including 4,610 colorectal cancer [CRC] cases) found no association of consuming raw or cooked garlic (three studies, four cohorts) or supplemental garlic (four studies, five cohorts) with CRC (127) . Another recent systematic review and meta-analysis that combined data from seven cohort and seven case-control studies also failed to find a statistically significant reduction in CRC risk with garlic intake (128) . Yet, these results are in contrast with previous pooled analyses of data from case-control studies (129) or from both case-control and prospective studies (130) that reported an approximate 30% lower CRC risk in individuals with the highest garlic intakes compared to those with the lowest intakes. Inclusion of case-control studies, which are more susceptible to bias, may explain these discrepancies among meta-analyses (128) . For information regarding different types of epidemiological studies , see the Spring/Summer 2016 LPI Research Newsletter .

A small preliminary intervention trial in 37 patients with colorectal adenomas examined whether supplementation with aged garlic extract for 12 months affected adenoma size and recurrence. Both the number and size of adenomas were significantly reduced in patients given a high dose of aged garlic extract compared to those given a much lower dose (0.16 mL/day) (131, 132) . Larger randomized controlled trials are needed to determine whether garlic or garlic extracts can substantially reduce adenoma progression to advanced cancer and recurrence.

Other types of cancer

In a small, placebo -controlled intervention study in 50 patients with cancer (42 with liver cancer, seven with pancreatic cancer, and one with colon cancer), supplementation with 500 mg/day of aged garlic extract for six months failed to prevent quality of life deterioration caused by disease progression and chemotherapy -associated adverse effects (133) . Yet, the active treatment limited the decline in natural killer cell count and activity that accompanies digestive cancer progression and reduces patient survival (133) .

At present, evidence from trials is limited and results from observational studies do not suggest a role of high intakes of garlic in the prevention of cancer in humans (112) .

Food sources

Allium vegetables, including garlic and onions, are the richest sources of organosulfur compounds in the human diet (134) . To date, the majority of scientific research relating to the health effects of organosulfur compounds has focused on those derived from garlic. Fresh garlic cloves contain about 2 to 6 mg/g of γ-glutamyl-S-allyl-L-cysteine (0.2%-0.6% fresh weight) and 6 to 14 mg/g of alliin (0.6%-1.4% fresh weight). Garlic cloves yield about 2.5 to 4.5 mg of allicin per gram of fresh weight when crushed. One fresh garlic clove weighs 2 to 4 g (5) .

Effects of cooking

The enzyme alliinase can be inactivated by heat. In one study, microwave cooking of unpeeled, uncrushed garlic totally destroyed alliinase enzyme activity (135) . An in vitro study found that prolonged oven heating or boiling (i.e., six minutes or longer) suppressed the inhibitory effect of uncrushed and crushed garlic on platelet aggregation, but crushed garlic retained more anti-aggregatory activity compared to uncrushed garlic (136) . Administering raw garlic to rats significantly decreased the amount of DNA damage caused by a chemical carcinogen , but heating uncrushed garlic cloves for 60 seconds in a microwave oven or 45 minutes in a convection oven prior to administration blocked the protective effect of garlic (137) . The protective effect of garlic against DNA damage can be partially conserved by crushing garlic and allowing it to stand for 10 minutes prior to microwave heating for 60 seconds or by cutting the tops off garlic cloves and allowing them to stand for 10 minutes before heating in a convection oven. Because organosulfur compounds derived from alliinase- catalyzed reactions may play a role in some of the biological effects of garlic, some scientists recommend that crushed or chopped garlic be allowed to "stand" for at least 10 minutes prior to cooking (135) .

Several different types of garlic preparations are available commercially, and each type provides a different profile of organosulfur compounds depending on how it was processed (see Table 1 ). Not all garlic preparations are standardized, and even standardized brands may vary with respect to the amount and the bioavailability of the organosulfur compounds they provide (5) .

Powdered (dehydrated) garlic

Powdered or dehydrated garlic is made from garlic cloves that are usually sliced and dried at a low temperature to prevent alliinase inactivation (138) . The dried garlic is pulverized and often made into tablets. To meet United States Pharmacopeial Convention (USP) standards, powdered garlic supplements must contain no less than 0.1% γ-glutamyl-S-allyl-L-cysteine and no less than 0.3% alliin (dry weight) (139) . Although powdered garlic supplements do not actually contain allicin, the manufacturer may provide a value for the "allicin potential" or "allicin yield" of a supplement on the label. These values represent the maximum achievable allicin yield of a supplement (140) . It is determined by dissolving powdered garlic in water at room temperature and measuring the allicin content after 30 minutes (139) . Because alliinase is inactivated by the acidic pH of the stomach, most powdered garlic tablets are enteric-coated to keep them from dissolving before they reach the neutral pH of the small intestine . It has been argued that it is more appropriate to measure "allicin release" using a USP method for assessing drug release from enteric-coated tablets under conditions that mimic those of the stomach and intestine (139) . Allicin release by this method has been shown to parallel true bioavailability (140) . Most tablet brands have been found to produce little allicin under these conditions, due mainly to low alliinase activity and prolonged disintegration times (140, 141) . Many manufacturers provide information on the "allicin potential" of their powdered garlic supplements, but few provide information on the "allicin release." A number of controlled clinical trials have examined the effect of powdered or dehydrated garlic supplements on cardiovascular risk factors (see Cardiovascular disease ). The most commonly used doses ranged from of 600 to 900 mg/day and provided 3.6 to 5.4 mg/day of potential allicin (90) .

Garlic fluid extracts (aged garlic extract™)

When garlic cloves are incubated in a solution of ethanol and water for up to 20 months, allicin is mainly converted to allyl sulfides, which are lost by evaporation or converted to other compounds (138) . The resulting extract contains primarily water-soluble organosulfur compounds, such as SAC and SAMC (see Figure 3 ) (142) . Garlic fluid extracts, including aged garlic extracts, are standardized to their S-allyl-L-cysteine content. In controlled clinical trials , daily intakes of aged garlic extract at doses between 1.2 g-2.4 g (containing 1.2 to 2.4 mg of S-allyl-L-cysteine) consistently resulted in reductions in SBP by 9 mm Hg-10 mm Hg and reductions in DBP by 4 mm Hg-8 mm Hg in a majority of patients with uncontrolled hypertension (110 , 143) . Additionally, aged garlic extract at doses of 2.4 to 7.2 g/day resulted in short-term reductions in ex vivo platelet aggregation (144) and reductions in serum cholesterol concentrations up to 12 weeks (16) .

Steam-distilled garlic oil

Steam distillation of crushed garlic cloves results in a product that contains mainly allyl sulfides, including DATS, DADS, and DAS (see Figure 2 ) (138) . These fat-soluble steam distillation products are usually dissolved in vegetable oil.

Garlic oil macerates

Incubation of crushed garlic cloves in oil at room temperature results in the formation of vinyldithiins and ajoene from allicin, in addition to allyl sulfides, such as DADS and DATS (see Figure 2 ) (5) . Ether extracts are similar in composition to garlic oil macerates but more concentrated (145) .

The most commonly reported adverse effects of oral ingestion of garlic and garlic supplements are breath and body odor (90 , 146) . Gastrointestinal symptoms have also been reported, including heartburn, abdominal pain, belching, nausea, vomiting, flatulence, constipation, and diarrhea (106) . The most serious adverse effects associated with oral garlic supplementation are related to uncontrolled bleeding. Several cases of serious postoperative or spontaneous bleeding associated with garlic supplementation have been reported in the medical literature (147-150) . Garlic may also trigger allergic responses in some individuals, including asthma in people with occupational exposure to garlic powder or dust (151) . Exposure of the skin to garlic has been reported to cause contact dermatitis in some individuals (146 , 152) . More serious skin lesions, including blisters and burns, have also been reported with topical exposure to garlic for six or more hours.

The safety characteristics of the various garlic preparations likely depend on their specific chemical composition (see Table 1 ). Aged garlic extract — the only water-based garlic supplement — showed a safe profile in toxicity studies and exhibited no undesirable side effects when combined with anticoagulants (warfarin), antiplatelets (aspirin), cholesterol-lowering (statins) drugs, or anticancer drugs (doxorubicin, 5-fluorouracil, methotrexate) in clinical settings (reviewed in 6 ). Safety and toxicity data are lacking for lipophilic ( hydrophobic ) garlic preparations, but some of their constituents have been shown to interfere with drug-metabolizing enzymes and transporters (see Drug interactions ).

No adverse effects on pregnancy outcomes have been reported when garlic is consumed in the diet. Although no adverse pregnancy outcomes were reported in a study of Iranian women who took dehydrated garlic tablets (800 mg/day) for two months during the third trimester of pregnancy (153) , the safety of garlic supplements in pregnancy has not been established. There is some evidence that garlic consumption alters the odor and possibly the flavor of breast milk. In a controlled cross-over trial , oral consumption of 1.5 g of garlic extract by lactating women increased the perceived intensity of breast milk odor (154) . Infants spent more time breast-feeding after their mothers consumed the garlic extract compared to a placebo , but the amount of milk consumed and number of feedings were not significantly different. Additionally, it is not known if topical use of garlic is safe during pregnancy or lactation.

Anticoagulant medications

Garlic may enhance the anticoagulant effects of warfarin (Coumadin). There have been two case reports in which prothrombin time ( INR ) increased in patients who started taking garlic tablets or garlic oil without changing their warfarin dose or other habits (155) . However, a more recent study in closely monitored patients on warfarin therapy found that garlic fluid extracts (aged garlic extract) did not increase hemorrhagic risk (156) . Since garlic supplements have been found to inhibit platelet aggregation (90) , there is a potential for additive effects when garlic supplements are taken together with other medications or supplements that inhibit platelet aggregation, such as high-dose fish oil or vitamin E (157) . More research is needed to determine whether garlic supplements are safe for people on anticoagulatory therapy.

HIV protease inhibitors

Supplementation of healthy volunteers with garlic caplets twice daily (allicin yield, 7.2 mg/day) for three weeks resulted in a 50% decrease in the bioavailability of the protease inhibitor, saquinavir (Fortovase) (158) . Although saquinavir undergoes significant metabolism by CYP3A4, supplementation with garlic extract for two weeks did not significantly alter a measure of CYP3A4 activity in healthy volunteers (159) . Garlic extract supplementation (10 mg/day) for four days did not significantly alter single-dose pharmacokinetics of the protease inhibitor, ritonavir (Norvir), but further research is needed to determine steady-state interactions between well-characterized garlic supplements and ritonavir (160) . In vitro hepatic models suggested that flavonoids and sulfur-containing compounds in garlic supplements might interfere with the activity of efflux drug transporters of the ATP-binding cassette (ABC) family, including P-glycoprotein, multidrug resistance protein (MRP), and breast cancer-resistance protein (BCRP), which function as ATP -dependent efflux pumps that actively regulate the excretion of a number of drugs limiting their systemic bioavailability . They may also affect the activity of phase I biotransformation enzymes like cytochrome P450 (CYP) 3A4 (CYP3A4) (161, 162) . Modifications of efflux transporter and CYP3A4 activities may explain how supplementation with garlic phytochemicals might hinder the therapeutic efficacy of medications like antiretroviral drugs (162) .

Originally written in 2005 by: Jane Higdon, Ph.D. Linus Pauling Institute Oregon State University

Updated in July 2008 by: Victoria J. Drake, Ph.D. Linus Pauling Institute Oregon State University

Updated in September 2016 by: Barbara Delage, Ph.D. Linus Pauling Institute Oregon State University

Reviewed in December 2016 by: Karin Ried, Ph.D., MSc. Research Director National Institute of Integrative Medicine

Copyright 2005-2024  Linus Pauling Institute 

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126.   Ernst E. Is garlic an effective treatment for Helicobacter pylori infection? Arch Intern Med. 1999;159(20):2484-2485.  (PubMed)

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132.   Tanaka S, Haruma K, Yoshihara M, et al. Aged garlic extract has potential suppressive effect on colorectal adenomas in humans. J Nutr. 2006;136(3 Suppl):821S-826S.  (PubMed)

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The Health Benefits of Garlic, According to Registered Dietitians

This small root vegetable packs a ton of flavor and an antioxidant punch!

Is garlic good for you?

Yes! While many studies have demonstrated the anti-inflammatory and anti-microbial benefits of garlic, there is also promising research that garlic could help in the prevention and management of certain types of cancer. Additionally, garlic's health benefits may reach even further to promote better gut health, help you to live longer, resist osteoporosis, and improve cardiovascular health. Below are eight science-backed ways garlic may benefit your health .

Health benefits of garlic

1. Garlic may have anti-viral effects

Garlic has long been associated with immune-boosting and anti-microbial benefits. Most of the health benefits found in garlic come from the sulfur compound allicin which is released when garlic is cut, crushed or chewed. A recent study suggests that garlic may boost the body's immune system to better deal with viral infections.

2. Garlic may reduce blood pressure and cholesterol

A recent review of studies found that garlic was shown to reduce blood pressure and cholesterol in patients with and without hypertension. Another study showed that garlic could lower unhealthy (LDL) cholesterol and triglycerides, and yet more research shows that aged garlic extract could reduce blood pressure in patients with uncontrolled hypertension. Plus, it may be effective in improving arterial stiffness and inflammation.

3. Garlic may boost gut health

Garlic contains the fiber inulin, a prebiotic, which is known to boost good gut bacteria. A recent study in mice showed that when they were given an oral supplement made from dried whole garlic, it reduced the negative effect a high-fat diet can have on cholesterol levels and on the microorganisms living in the intestinal system (a.k.a. gut microbiome).

4. Garlic may have anti-cancer properties

According to the American Cancer Society , colorectal cancer is the third most common cancer in both men and women. A recent study involving 833 people in China found that consumption of vegetables containing allium (like garlic, leeks and onions) was associated with a lowered risk of colorectal cancer.

“Reports from the American Institute for Cancer Research show that eating garlic frequently may lower the risk of certain cancers such as colorectal cancer by helping with DNA repair, slowing the growth of cancer cells and decreasing inflammation," says Stefani Sassos , MS, RDN, CSO, CDN, Deputy Director of the Good Housekeeping Institute Nutrition Lab.

5. Garlic may contribute to longevity

One recent study that looked at more than 27,000 individuals in China, found that regular consumption of garlic was associated with lowered all-cause death risk. The study produced statistically significant findings that showed eating garlic could extend life by half a year.

6. Garlic may have anti-inflammatory benefits

One study that looked at women with rheumatoid arthritis found pain intensity, tender joints and fatigue were significantly decreased, compared to the control group, when they took a supplement containing 1000 mg of garlic. Additionally, the Arthritis Foundation recommends consuming garlic due to its antioxidant and anti-inflammatory compounds .

7. Garlic may help to improve bone health

A study in Iran involving garlic extract looked at post-menopausal women with osteoporosis. The study findings indicated that orally administered garlic supplements could facilitate calcium absorption which can lead to stronger bones.

8. Garlic may improve cognitive function

While studies in humans are limited, animal studies have recently shown that consuming aged garlic extract could play a positive role in preventing the decline of learning and cognitive memory functions that are associated with Alzheimer’s disease.

How to include more garlic in your diet

Allicin, the active molecule in garlic , contains many possible health benefits and antibacterial properties and is released by chopping or crushing garlic. Studies have shown that this active compound can be destroyed by heat, so consuming raw garlic is the best way to get all the benefits.

"After chopping or crushing garlic, allow it to sit for approximately 10 minutes before adding to food or cooking. The reason lies in giving the enzyme alliinase time to fully develop and produce the active compound allicin," says Sassos.

When it comes to storing garlic , keep unpeeled garlic at room temperature and place peeled garlic in the fridge. If you have a lot of garlic on hand, it can be stored in the freezer.

Side effects of garlic

In addition to causing bad breath, garlic may contribute to gas and bloating in some people, especially those who have IBS. Garlic is considered a high FODMAP food, so if you have IBS or are following a low FODMAP diet , you may want to proceed with caution or avoid it altogether.

If you are currently taking blood thinners, such as warfarin (Coumadin), you should consult with your physician before you increase your garlic intake, as garlic can interfere with certain blood thinning medications.

If you find that you are sensitive to garlic, there are other potential ways you can include it in your diet. Try cooking with a whole garlic clove and removing it before eating your dish or using garlic-infused oil.

The bottom line

Garlic not only adds flavor to your meals, but the evidence shows that it has promising anti-viral powers and it can be used as an anti-inflammatory that is easily accessible with few, if any, side effects. There are also suggestions that it works to decrease the risk of certain cancers, as well as promising evidence that it may be useful in the fight against cognitive decline, among other benefits.

While there is no recommended daily limit on how much to eat, it is "generally recognized as safe" (GRAS) by the U.S. Food and Drug Administration. A good rule of thumb is to consume in moderation. If you are considering consuming garlic as an oral supplement, we recommend consulting with your healthcare provider first.

Amy (she/her) is a registered dietitian with the Nutrition Lab at the Good Housekeeping Institute , covering nutrition- and health-related content and product testing. She holds a bachelor's degree in journalism from Miami University of Ohio and a master's degree in clinical nutrition from NYU. Prior to Good Housekeeping , she worked at one of the largest teaching hospitals in New York City as a cardiac transplant dietitian. She has authored numerous chapters in clinical nutrition textbooks and has also worked in PR and marketing for food company start-ups.

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The Health Benefits of Garlic

It's touted as a way to protect against heart disease, cancer, and infection. here's what garlic can do for you., sharing is nice.

We respect your privacy . All email addresses you provide will be used just for sending this story.

There's nothing like a little garlic to punch up a stir-fry, roast chicken, or pasta dish, but for centuries it has been purported to add some oomph to your health , too.

Ancient civilizations used garlic to treat asthma, digestive disorders, heart disease, infections, respiratory disorders, tumors, and even intestinal worms. Today, claims for the health benefits of garlic include lower blood pressure and cholesterol, an anti-inflammatory effect, a reduced risk of cancer, and a stronger immune system.

While many of these claims are overblown, there is evidence of some health benefits. Here is what you should know about this pungent allium, and how to reap its benefits. 

What Makes Garlic Special

Garlic's odoriferous flavor comes from sulfur compounds made from allicin, an active ingredient once thought to be responsible for the health benefits of garlic. But it has as many as 40 other compounds, and "any number or combination of them may be responsible for its healthfulness," says Matthew Budoff, M.D., a professor of medicine at the Los Angeles Biomedical Research Institute who studies the effects of garlic on cardiovascular health .

Most of the studies on the health benefits of garlic used garlic supplements because they provide a consistent dose, though others used garlic powder, garlic oil, and a Japanese method of preparing garlic that involved kneading and pulverizing crushed garlic together with egg yolk.

Budoff says the strongest evidence for the health claims suggests that garlic may help the heart, with data overall showing about a 10 percent reduction in cholesterol and a three to eight point drop in blood pressure.

"That isn't quite as good as cholesterol or blood pressure pills," he says, "but it's certainly a nice effect."

A review of studies published in the journal Neurological Research in March, for instance, concluded that garlic and some of its various preparations (such as garlic extract or powder) could be a helpful side therapy for those already being treated for cardiovascular disease, high blood pressure,  and diabetes ; and potentially may even reduce the risk of heart attack and stroke. 

Another study published in 2017 involving an analysis of nine clinical trials with a total of 768 patients with type 2 diabetes found that those who took 50 to 1,500 mg of a garlic supplement each day for two or three months had significant reductions in their fasting blood glucose levels.

And in an earlier, smaller study of 55 people with metabolic syndrome—a group of risk factors, such as excess stomach fat or high blood pressure, that raise the  risk of heart disease —published in the Journal of Nutrition, Budoff and his colleagues found that those who took a daily garlic supplement for a year had slower plaque buildup from coronary artery disease than those who took a placebo. 

A Hint of Caution

But many studies showing a  cardiovascular benefit , though rigorous, are small, and not every study shows that garlic is beneficial. There has even been concern that garlic supplements may be harmful for some people with heart disease.

A research review published in the Journal of the American College of Cardiology found that garlic (along with green tea, ginkgo, ginseng, and hawthorn) can interfere with the efficacy of some  heart medications  or increase their side effects.

For example, too much garlic can pose a bleeding risk for people on anticoagulants such as warfarin (Coumadin, Panwarfin) or a prescribed aspirin regimen. It may also make some other drugs less effective, such as saquinavir, a drug used to treat HIV infection, according to the National Institutes of Health.

The authors of the review also noted that garlic (and other herbal supplements) has "limited evidence of benefit," meaning it might help but more research is needed.

The research is even weaker for garlic's ability to fight bacteria,  ward off colds , boost the immune system, or reduce the risk of certain cancers, such as stomach or colon cancer.

"There's a lot of purported benefits of these medicines [garlic supplements]," says Budoff at the Los Angeles Biomedical Research Institute. "I'm more comfortable with the research on the cardiovascular benefits of garlic, and I'm less comfortable with it curing the common cold, acting as  an antiviral , or other therapies." 

Garlic in Your Dinner

Perhaps for these reasons, experts say the best way to get your garlic is from the fresh clove, although there can be a few "side effects" from eating it fresh. Garlic breath is probably the worst of it, but some people do suffer from indigestion after eating fresh garlic.

A less stinky and easier-on-the-stomach alternative may be black garlic, which is "aged" under intense heat and humidity for 10 days, turning the bulbs black and purportedly giving the allium a sweeter, more sour taste with a jelly-like consistency. This aging process rids the garlic of its pungent, irritating properties, but the benefits remain. 

Garlic is an essential part of the Mediterranean diet , "which has been shown to have the best long-term outcomes of any diet we know of," says Budoff. Studies have linked this way of eating—which emphasizes produce, legumes, grains, and healthy oils, with small amounts of fish and meat—to a better quality of life, a lower risk of chronic disease, and better brain health in older adults.

"I use garlic in a lot of recipes," says Ellen Klosz, a Consumer Reports nutritionist. "You can use it to spice up a healthy dish without having to add any salt. Just make sure to use fresh garlic instead of garlic salt, which will boost the sodium levels."

How to Get the Most Out of Garlic

Choose the freshest bulbs. Look for plump bulbs with tight skin that isn't frayed, loose, dried out, or moldy. Sprouting, too, is a sign of age. The fresher the garlic, the higher the concentration of its active ingredients, Budoff explains. Though garlic can keep for months, he says it's best to eat it within a week. "If you go longer than that," he says, "you can end up with something that's deactivated." 

Store it right. Keep garlic in a cool, dark place with good ventilation to prevent it from getting moldy or from sprouting.

Chop it for your health. Chopping , slicing, or smashing garlic triggers an enzyme reaction that increases its healthful compounds. Heat prevents this reaction, so let garlic sit on the cutting board for at least 10 minutes before cooking.

Minimize garlic breath. The smell of garlic can stay on your breath and be excreted by the lungs for a day or two after you eat it. A study published in the Journal of Food Science in 2016 suggests that munching on raw mint leaves, apples, or lettuce after a garlicky meal can help by neutralizing the sulfur compounds in garlic responsible for its odor.  

Julia Calderone

I'm a former scientist, using words and an audio recorder as my new research tools to untangle the health and food issues that matter most to consumers. I live in Brooklyn, N.Y., where I cook as much as possible. You can find me in the grocery aisle scrutinizing the fine print of every food item I put into my cart. Follow me on Twitter @juliacalderone .

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Here’s how you know

• U.S. Department of Health and Human Services
• National Institutes of Health

Common Names:  garlic

Latin Names:  Allium sativum

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• Garlic is the edible bulb from a plant in the lily family. It was traditionally used for health purposes by people in many parts of the world, including the Egyptians, Greeks, Romans, Chinese, and Japanese.
• Currently, garlic is most commonly promoted as a dietary supplement for conditions related to the heart and blood vessels, including high blood cholesterol and high blood pressure.
• Fresh garlic, garlic powder, and garlic oil are used to flavor foods. Garlic may be used topically (applied to the skin).

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• A great deal of research has been done on garlic, especially on garlic’s effect on high blood lipid levels (hyperlipidemia) and high blood pressure (hypertension).

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• While there’s conflicting evidence, the most reliable results suggest that taking garlic supplements may reduce total cholesterol and low-density lipoprotein (LDL) cholesterol levels in people with high levels of these blood lipids. If it does, the effect is small, and it may take more than 8 weeks before noting any improvement. Taking garlic doesn’t appear to improve high-density lipoprotein (HDL) levels or triglycerides (another blood lipid).
• Garlic supplements may be helpful for high blood pressure, but the evidence is limited.
• The most reliable research has found that intake of garlic as a food or supplement is not associated with a reduced risk of developing gastric cancer. However, epidemiologic studies suggest a link between higher intakes of vegetables in the garlic family (which includes onions, shallots, chives, and leeks as well as garlic) and lower risks of certain cancers, particularly gastrointestinal cancers.
• There’s not enough evidence to show whether garlic is helpful for the common cold.

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• Garlic is probably safe for most people in the amounts usually eaten in foods.
• Little is known about whether it’s safe to use garlic supplements or apply garlic to the skin during pregnancy or while breastfeeding.
• Side effects include breath and body odor, heartburn, and upset stomach. These side effects can be more noticeable with raw garlic. Some people have allergic reactions to garlic.
• Taking garlic supplements may increase the risk of bleeding. If you take an anticoagulant (blood thinner), such as warfarin (Coumadin), or if you need surgery, tell your health care provider if you’re taking or planning to take garlic supplements.
• Garlic supplements may interfere with the effectiveness of some drugs, including saquinavir, a drug used to treat HIV infection. Garlic supplements may also interact with some dietary herbs and other supplements.

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• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

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• Using Dietary Supplements Wisely
• Know the Science: H ow Medications and Supplements Can Interact
• Know the Science: How To Make Sense of a Scientific Journal Article

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

Telecommunications relay service (TRS): 7-1-1

Website: https://www.nccih.nih.gov

Email: [email protected] (link sends email)

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed .

Website: https://pubmed.ncbi.nlm.nih.gov/

Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need To Know ) and fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements).

Website: https://ods.od.nih.gov

Email: [email protected] (link sends email)

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• Garlic. Natural Medicines website. Accessed at naturalmedicines.therapeuticresearch.com on July 5, 2020. [Database subscription].
• Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database of Systematic Reviews. 2014;(11):CD006206. Accessed at https://www.cochranelibrary.com on August 27, 2020.
• Nicastro HL, Ross SA, Milner JA. Garlic and onions: their cancer prevention properties. Cancer Prevention Research. 2015;8(3):181-189.
• Pazyar N, Feily A. Garlic in dermatology. Dermatology Reports. 2011;3(1):e4.

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

Related Topics

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• Updated: February 16, 2024
• Originally Published: August 3, 2022
• Lisa Rosenberg M.S, M.B.A

The Top 10 Health Benefits of Garlic

Did you know that the average person consumes 2 pounds of garlic each year?

For thousands of years, before this spice was used to flavor your favorite dishes, it was employed as a medical treatment in ancient cultures. The health benefits of garlic were used by Chinese, Egyptian, and Roman civilizations. There is substantial documentation of their usage of garlic for its medicinal properties.

Garlic consumption has been shown to have numerous fantastic health benefits for the body. From ancient times to modern research, garlic has maintained its reputation as an incredible natural remedy. Let’s look at the most crucial health benefits of garlic and understand why this kitchen staple is so good for you.

Why Is Garlic Healthy For You?

Though it was not widely known, experts now understand that sulfur compounds contribute heavily to the health benefits of garlic.

By slicing, chopping, or crushing garlic bulbs, the thio-Sulfinite chemicals in them are converted into allicin—a fantastic substance that is a primary source of the health benefits of garlic. However, while this appears to be true in theory, let’s dive deeper into the actual health benefits of garlic.

1. Garlic Helps Boost Your Body's Immune System

Your body’s immunity is what keeps it from getting sick in the first place, and it also aids in the fight against illness when the situation calls for it. Garlic offers an immune system boost to help prevent colds and the flu virus.

Children get six to eight colds each year, while adults get two to four. The health benefits of garlic shine in its ability to protect against cough, fever, and cold illnesses, even when eating it raw.

In fact, eating two chopped garlic cloves every day is the best way to benefit. In some households around the world, families hang garlic cloves on a string around their children’s necks to help them with congestion. The powerful immune-boosting benefits of garlic make it a culinary superfood for protecting against common ailments.

2. Garlic Helps Reduce High Blood Pressure

Strokes and heart attacks are two of the most significant health concerns worldwide. High blood pressure is a considerable risk factor for heart disease. It’s thought to cause about 70% of strokes, heart attacks , and chronic heart failure. High blood pressure is the cause of 13.5 percent of deaths worldwide.

Because they are among the most significant causes of death, addressing one of their primary causes, high blood pressure, is extremely important.

Garlic is a fantastic spice to include in your diet for those suffering from high blood pressure or hypertension. However, even if you are not a lover of garlic, try minced garlic which has a milder flavor. It will still give you the health benefits of garlic, such as lowering high blood pressure, treating fever, and many more.

Keep in mind that you must make sure that the amount of pre-prepared garlic you consume is the same as four cloves of garlic each day. Be sure to talk to your doctor before changing your diet.

3. Garlic Helps Reduce Cholesterol Levels

Cholesterol is a fatty and critical component in the blood. There are two kinds of cholesterol: “bad” LDL cholesterol and “good” HDL cholesterol. An imbalance, with too much LDL cholesterol and not enough HDL cholesterol, can lead to some serious health issues.

Garlic has been shown to lower total cholesterol and LDL levels by 10 to 15 percent.

Furthermore, eating garlic does not influence your HDL or good cholesterol levels. If you have a family history of heart disease or are dealing with heart-related issues, incorporating garlic into your diet can be a natural and flavorful step towards a healthier heart.

4. Garlic Can Help With Prevention of Cancer

The health benefits of garlic don’t end with the heart. Here is another reason why your body can benefit from an extra dose of this onion family member.

The health benefits of garlic, particularly in the realm of cancer prevention, have become more of a subject of interest. According to research, consuming fresh garlic can help lessen the risk of colon cancer. Similarly, according to the Iowa Women’s Health Study, women who ate garlic regularly with other vegetables and fruits had a 35% lower chance of getting colon cancer.

However, researchers agree that more studies are still needed in this area to fully comprehend the extent of the health benefits of garlic in preventing cancer.

5. Garlic Has Antibiotic Properties

Garlic contains allicin, a bioactive antibiotic that can help fight infections and bacteria when cloves are sliced, squashed, or diced. These health benefits of garlic extend to suppressing the growth of potentially harmful substances, like:

• fungi elements
• Protozoa elements
• viral infections
• numerous bacteria like Salmonella

Allicin is considered a potent natural antibiotic, and its effectiveness is noteworthy. When it’s used in conjunction with conventionally prescribed antibiotics, garlic can provide added support in battling infections.

6. Garlic May Prevent Alzheimer’s and Dementia

Garlic, with its high volume of antioxidants, can help prevent oxidative damage from occurring in your body. These antioxidant properties can help prevent certain cognitive diseases, like dementia and Alzheimer’s.

While the health benefits of garlic are noteworthy, you should still approach this claim with a pinch of, well, garlic. It’s important to note that taking high doses of garlic supplements doesn’t grant you immunity to these diseases. The medicinal properties of garlic can only improve health to a certain point.

7. Garlic Can Improve Athletic Performance

This ingredient is one of the earliest performance enhancers available. In ancient times, the health benefits of garlic were used to alleviate weariness and boost the endurance of laborers. Even Greek Olympic athletes would consume garlic to enhance their athletic performance.

Here are just a few of the athletic benefits of garlic:

• Managing cholesterol levels
• Lowering blood pressure
• Boosting immunity
• Reducing the length of illness

A healthy heart and body are key to maintaining your fitness. Ultimately, incorporating garlic into your diet helps delay fatigue during physical exertion, making it a natural ally for those aiming to enhance their athletic performance.

8. Garlic Helps Detox Your Body

Detoxification is the process of getting rid of things that don’t belong in the body, and it plays an important role in maintaining good health and longevity.

In our day-to-day lives, we are exposed to a wide range of chemicals and compounds. Many of these compounds are not healthy and may even be detrimental to the body. Some of these chemicals and compounds include:

• Pesticides and chemicals used in agriculture
• Radiation etc from nuclear plants
• Personal care products containing chemicals
• Household cleaners
• Other household products

Garlic is a powerful detox food that promotes glutathione production by various liver enzymes. It also provides other important detoxifying components, including multiple bioactive selenium and sulfur compounds. By incorporating garlic into your diet, you not only add rich flavor to your dishes but also assist your body in the crucial task of detoxifying from the challenges of the modern world.

9. Garlic Packs a Low-Calorie Health Punch

Garlic is a tasty way to add nutritional benefits without sacrificing many of your daily calories. One clove of garlic is a nutritional powerhouse, containing essential nutrients like B6, fiber, and selenium.

These components not only enhance the taste of your meals, but may also contribute to positive effects on blood pressure and cholesterol levels. By embracing these health benefits of garlic you can savor some low-calorie goodness in every bite.

10. Garlic May Improve Bone Health

Garlic has also emerged as a valuable ally for bone health , particularly in menopausal women. When women experience bone loss during menopause due to reduced estrogen production, garlic can assist in reducing oxidative stress.

Garlic plays a supportive role by encouraging estrogen production, potentially halting bone loss and offering protection against conditions like osteoarthritis. Fortifying your bones and safeguarding against age-related bone concerns is yet another natural benefit of garlic.

Keep Calm and Garlic On!

Now that we have discussed the health benefits of garlic, whether raw or taken as a supplement, you can take the first step to a healthier, better you. Not to mention that there are even more healthy advantages to using Spice World when you incorporate the delicious health benefits of ginger and the health benefits of onions too!

Would you like to find out more about our garlic products that are fit for every occasion?

Then contact us whether you prefer conveniently minced garlic, easy-to-use peeled cloves or whole bulbs. Our garlic will impart a strong, delicious taste to your cuisine!

The Best Garlic Lemon Vinaigrette & Weeknight Salad

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List of Sources:

6 Fun Facts About Garlic

Three Reasons a Heart Loves Garlic

Garlic Health Benefits

Garlic Lowers Blood Pressure…

Garlic for the Common Cold

Garlic Nutrition Facts and Health Benefits

11 Proven Health Benefits of Garlic

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Garlic: Planting, roasting and understanding the health benefits of the plant

G arlic is an excellent, nutritious ingredient used in a variety of large meals and small recipes for centuries throughout the world. 

Civilizations across human history have used garlic for medicinal purposes and to add flavor to food. The plant is in the same family as onions, leeks and shallots , which share similar benefits. 

Read below to understand the health benefits of moderate daily garlic consumption . 

MAN STUCK GARLIC CLOVE IN EAR IN BID TO GET RID OF INFECTION, LEFT IT FOR 2 MONTHS, REPORT SAYS

Garlic offers numerous health benefits and adds flavor to a variety of meals that are easy to prepare for a family or individual. 

However, If you consume garlic on a daily basis, you should do so in moderation and decrease your intake if you notice negative side effects. 

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In general, overconsumption of garlic will produce side effects, including garlic breath, digestive issues, bloating, stomach pains, gas and heartburn. 

A safe amount of garlic for an individual to consume a day, generally speaking, is between one and two cloves or three to six grams. While there is no official recommendation on the exact daily garlic consumption, if you notice any of the negative side effects, reduce your consumption or stop eating it altogether if necessary. 

It may be better to consume garlic by cooking or preparing it for your meals during lunch or dinner. This option will allow you to eat in a more safe and efficient manner (and may help to reduce garlic breath and acid refluxes).  

There are a variety of meals in which garlic can be incorporated that will reduce your chance of having bad breath while also being able to enjoy the garlic flavor. 

If you enjoy red meat, you can pan-sear a New York strip steak for between 6 and 10 minutes, depending on your preference, alongside a few pieces of crushed garlic. You can cut open a garlic clove ahead of time and rub the clove across the meat before cooking for just a touch of garlic flavor. 

If you choose to cook in butter, avoid cooking the garlic for more than 30 seconds, as it will brown and burn. Include herbs such as thyme or rosemary to add even more flavor. 

Garlic can also be enjoyed in various side dishes, such as grilled asparagus, mixed into mashed potatoes or cooked carrots with roasted garlic. You can also add a healthy dose of garlic in different forms in sandwiches, bread, soups, pasta, chicken and homemade pizzas. 

By cooking garlic as an ingredient within a wider meal, you can enjoy the taste and health benefits of the plant while avoiding the negative effects.

THIS IS THE BEST WAY TO CURE GARLIC BREATH, ACCORDING TO SCIENCE

Over the years, medical research has determined that garlic provides individuals with several health benefits in the raw and supplements form. As previously mentioned, garlic can be enjoyed in a number of ways, including in the liquid form of tea. 

However, when it comes to the overall health benefits, moderate consumption of garlic can help individuals reduce the risk of infections due to the plant's ability to fight viruses, fungi and parasites. 

Additionally, garlic benefits cardiac health by helping the heart recover after a heart attack. A study from Emory University found that garlic oil helped reduce the damage to a heart attack to cardiac tissue by 61%. Other garlic supplements may also help individuals with hypertension reduce their blood pressure.

Finally, garlic can also act as a nutritious food supplement in an individual daily diet. For example, the plant is low in calories but is a good source of vitamin C, vitamin B6, manganese and other nutrients. However, although garlic has a lot of health benefits, it is important to moderate your consumption, make changes when necessary, and consult with your doctor.

One of the most delicious ways to use garlic in recipes is roasting it ahead of time and either mashing it or keeping it whole for your meal. 

To roast garlic, you'll need foil and an oil of your choosing. Remove the garlic cloves from the root and peel all the skin. There will be two layers of skin you'll want to avoid cooking. The first layer is a super frail skin that will fall off into pieces easily. The second layer is the stiff skin around the clove. 

This will be more laborious to peel so if you need assistance, cut one of the clove ends off and peel the garlic from there.  

Place your cloves on a piece of tinfoil and cover in oil, preferably extra virgin olive oil. If you're hoping for a pungent scent and flavor, include strong herbs like rosemary and thyme and wrap with your garlic. Roast the garlic in the oven at 450 F for 40 minutes. 

You'll want the cloves to be soft and mash to a fork when removed.

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Like other vegetables including lettuce, onions, potatoes, celery, beets and more, you can grow garlic from scraps or store bought bulbs.

If you're hoping to grow garlic at home, you can follow a fairly simple process. Here are tips for growing garlic.

• Separate your garlic from the outer layer of skin only. You'll want to keep on the inner layer of skin to ensure its growth.
• Plant individual cloves of garlic in loose potting mix. You can use a planter pot or raised bed to grow garlic.
• Plant the cloves in one to two inches below the surface and space them three to four inches apart to allow them room to grow.
• Mulch with an organic mixture and water once every seven days. Garlic takes six to eight months to harvest so be patient and enjoy after a winter and spring of germination.
• National Garlic Day is on April 19 every year.
• In 2020, 346 million pounds of garlic was produced in the U.S., which was valued at $246 million, according to the USDA.
• Garlic and onions come from the same plant family, Allium, which is actually a flower.
• Researchers have said that garlic can help prevent the most common type of arthritis, hip osteoarthritis.
• In Gilroy, California, there is an annual garlic festival with a garlic mascot, tons of food cooked with garlic and even garlic ice cream.
• Drinking lemon water will help with bad breath from garlic.
• Garlic is toxic for pets.

Exercise habits in youth create better health outcomes for some

Forming a long-term recreational exercise habit as a young person has a beneficial impact on physical and mental health later in life, but some groups, such as females and academic high-achievers, miss out on these benefits disproportionately.

A University of Adelaide study found females, people with low self-efficacy, reluctant exercisers, higher academic achievers, and those experiencing socioeconomic disadvantage are all most at risk of failing to establish regular exercise patterns during the transition from adolescence to young adulthood.

The finding was made by examining data collected as part of the Longitudinal Survey of Australian Youth (LSAY), which also showed young Australians on average exercise less regularly every year after transitioning from high school to university and work.

"It is well known that sustained regular exercise in young people improves fitness, physical health, self-esteem, reduces distress and sets up long-term patterns that reduce disease risk in adulthood," said Associate Professor Oliver Schubert from the University of Adelaide's Adelaide Medical School and the Northern Adelaide Local Health Network.

"There seems to be a critical period in people's teens, around the age of 15, to establish these behaviours."

While women's sport is increasing in prominence, the researchers say multiple factors contribute to the gender disparity.

"The disadvantage experienced by females is influenced by reduced opportunity, lower access, and lack of sports diversity, but also divergent parental and cultural expectations, stereotypes, and role models," says Dr Julie Morgan, Clinical Associate Lecturer at the University of Adelaide's Discipline of Psychiatry and lead author of the study.

"Psychological factors, such as perceived sports competency and self-efficacy, may play an additional role. Our study highlights that more needs to be done to promote long-term regular of exercise to female adolescents."

Females were not the only at-risk group that came as a surprise to the researchers.

"The risk for academic high achievers was unexpected and highlights the need to promote a balance between study and self-care to this group," said Associate Professor Scott Clark, Head of the University of Adelaide's Discipline of Psychiatry.

Prior research has shown similar findings regarding the benefits of forming exercise habits, but the LSAY data provides a clearer understanding than previously possible.

"The large size and high follow-up rate of LSAY, which follows Australian youth as they transition from school to study or work, makes it an extremely valuable resource for analysing the impact of changes in society and policy that can influence educational, occupational and physical- and mental-health outcomes," says Jana Bednarz, a senior statistician from the University of Adelaide who conducted the longitudinal modelling analyses.

"Our trajectory-based analysis of repeated measurements provides more robust data than previous cross-sectional studies, where data are collected only once, and therefore provides good evidence for youth exercise policy development in Australia."

The researchers say outreach is required at an early stage to encourage the at-risk groups they've identified to develop long-term exercise habits.

"Given the predictors of these patterns are identifiable at age 15, there is a key role for secondary school, especially in the last years, when academic achievements become more central for young people," said Associate Professor Schubert.

"Equally, universities and vocational training institutions could run programs to support and encourage physical activity and sport.

"State governments and local councils need to ask whether the current leisure infrastructure supports the needs of young people. Funding and support for grass-roots community sport across gender and socioeconomic groups is critical."

• Chronic Illness
• Teen Health
• Healthy Aging
• Child Psychology
• K-12 Education
• Child Development
• Gender Difference
• Developmental disability
• Anaerobic exercise
• Health benefits of tea
• Aerobic exercise
• Hyperactivity
• Physical exercise

Story Source:

Materials provided by University of Adelaide . Original written by Johnny von Einem. Note: Content may be edited for style and length.

Journal Reference :

• Julie Ayliffe Morgan, Jana Maria Bednarz, Ronnie Semo, Scott Richard Clark, Klaus Oliver Schubert. Long-term recreational exercise patterns in adolescents and young adults: Trajectory predictors and associations with health, mental-health, and educational outcomes . PLOS ONE , 2024; 19 (3): e0284660 DOI: 10.1371/journal.pone.0284660

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What Happens to Your Body When You Drink Apple-Cider Vinegar Every Day

Is sipping on ACV really the cure-all people make it out to be?

Lauren is an award-winning registered dietitian, author of three books and all-around lover of good food. After graduating with a bachelor's degree in food science and human nutrition and a master's degree in clinical nutrition, Lauren has worked in various nutrition-related settings, most currently writing nutrition-related content for online outlets including Verywell Health, PopSugar, The Kitchn, and EatingWell. Additionally, she manages the Instagram page @LaurenLovesNutrition, where people can receive evidence-based nutrition tips and updates.

Emily Lachtrupp is a registered dietitian experienced in nutritional counseling, recipe analysis and meal plans. She's worked with clients who struggle with diabetes, weight loss, digestive issues and more. In her spare time, you can find her enjoying all that Vermont has to offer with her family and her dog, Winston.

• Health Benefits

Frequently Asked Questions

Apple-cider vinegar, often referred to as ACV, is a staple in many kitchens for its culinary properties, being an acidic addition to salad dressings , sauces and so much more. And in the wellness world, some people tout apple-cider vinegar as a natural Jack-of-all-trades remedy, suggesting that it can be a solution for many ailments, including digestive concerns, obesity and more.

Since being brought to market as an approachable natural remedy in the early 1900s by Dr. Paul C. Bragg (yes, the same name you see on many ACV bottles), this vinegar’s popularity in the wellness space has exploded in recent years, with half of all Americans saying that they currently are using or have used it for health and wellness reasons, per a 2022 poll conducted by Bragg Live Food Products, Inc .

This type of vinegar is made from the fermentation of apples. Once the apples are juiced, the liquid is fermented with bacterial and yeast cultures. This transforms the sugars in the apple juice into alcohol, and then to vinegar.

Some ACV varieties have “the mother” advertised on their label, which refers to the combination of yeast and bacteria formed during the fermentation process. This substance, which looks like a cloudy sediment, is often visible at the bottom of the bottle, and it is believed to be rich in health-boosting natural proteins, healthy bacteria and acetic acid.

ACV contains a variety of flavonoids, such as gallic acid, catechin, caffeic acid and ferulic acid, according to research in BMC Complementary Medicine and Therapies in 2021. When you consume ACV, you take in these compounds, which may be one reason why people experience certain positive health outcomes.

But what really happens if you drink apple-cider vinegar every day? Along with giving your taste buds an acidic zing, drinking it may provide your body with some impressive benefits.

What Happens If I Drink Apple-Cider Vinegar Every Day?

You may experience better blood sugar management.

Apple-cider vinegar is often hailed as a beneficial tool for blood sugar regulation, with some studies supporting its positive impact on glycemic control. The acetic acid found in apple-cider vinegar is believed to slow the digestion of carbohydrates, thereby reducing the rate at which sugars enter the bloodstream and helping to maintain more consistent blood sugar levels. It may also improve insulin sensitivity, which plays a key role in the body's ability to effectively use glucose for energy.

A systematic review and meta-analysis, published in the aforementioned BMC Complementary Medicine and Therapies research, evaluated nine studies to determine whether ACV may affect blood sugar management. Results showed that consumption is linked to improved fasting plasma glucose and hemoglobin A1C concentrations (a measure of your average blood sugar over three months). While results did not show that ACV impacts fasting insulin, the authors did conclude that ACV appears to be a safe natural supplement that may help control blood sugar.

It is important to note that, while promising, these effects should not be considered a replacement for medical treatment in individuals with diabetes.

You May Have Better Digestive Health

In addition to its potential role in blood sugar regulation, apple-cider vinegar is often touted for its beneficial effects on digestive health. The “mother” in apple-cider vinegar is a source of probiotics, which are beneficial bacteria that contribute to a healthy gut microbiome. Probiotics support digestion and may even enhance nutrient absorption, according to a review in Cureus in 2022. Note that pasteurized ACV doesn’t contain live probiotics.

While many people report improvements in digestive health when consuming apple-cider vinegar, scientific studies on these effects are limited and more research is needed.

You May Lose Weight

Apple-cider vinegar is often cited as a natural tool for weight loss. The thought behind this claim primarily revolves around the presence of acetic acid, which some research, such as a review in Nutrients in 2019, says may suppress appetite.

A 2022 meta-analysis in Current Developments in Nutrition evaluated short- and long-term studies conducted on apple-cider vinegar and appetite and calorie intake. Results showed four of the six short-term studies reported that vinegar suppressed appetite. However, none of the long-term studies reported any appetite-suppressing benefit.

Apple-cider vinegar can complement a balanced diet and regular exercise to potentially support weight-loss goals. However, it is unlikely that adding this vinegar alone to the diet without other healthy lifestyle changes will make a major impact on one’s weight.

You May Benefit from Antimicrobial Properties

Apple-cider vinegar may have antimicrobial properties when it is consumed at full-strength concentrations. And some evidence suggests it may have antifungal activity as well.

The antimicrobial properties are likely due to the total phenolic contents of ACV, per data published in the International Journal of Microbiology in 2021. This study focused on the potential sanitizing properties of ACV. As for whether it can prevent or treat illness? That’s not as promising. So far, research has not shown that it’s effective against the influenza virus, per a study in 2019 in Natural Product Research .

You May Have Better Heart Health

Heart health can be a result of many factors, including some that are out of your control (like your family history). And when it comes to diet, including apple-cider vinegar in your routine may have some heart-health benefits, according to some (but not all) data.

Results from the earlier mentioned meta-analysis and systematic review showed that ACV consumption significantly decreased serum total cholesterol levels. And results of a 2023 randomized clinical trial in Frontiers in Clinical Diabetes and Healthcare evaluating the effects of consuming ACV among people with type 2 diabetes showed that consuming 30 milliliters of ACV per day for eight weeks resulted in a reduction in the LDL-to-HDL ratio, which is a positive heart-health outcome.

Risks and Precautions

While apple-cider vinegar has numerous potential health benefits, it's also essential to be aware of its potential risks and side effects. Topical application of undiluted apple-cider vinegar can lead to burns, irritation and discomfort due to its high acidity. And for those with stomach ulcers, consumption of acidic foods, like apple-cider vinegar, can exacerbate the condition.

Consumption of ACV may result in lower potassium levels, reports a 2020 review in the European Journal of Nutrition , which can result in heart-health concerns. ACV may also interact with certain types of drugs, potentially altering their effects on the body. Particularly, it may affect diabetes medications, diuretics and certain heart disease medications, according to the National Library of Medicine .

Certain groups of people should exercise caution when considering the use of apple-cider vinegar. Pregnant and breastfeeding women, for instance, should use it sparingly since there's insufficient research to confirm its safety during these periods. Individuals with diabetes, particularly those on insulin or other glucose-lowering medications, should monitor their blood sugar levels closely due to the vinegar’s potential to reduce blood sugar. People with a history of gastric ulcers or acid reflux may find that apple-cider vinegar exacerbates their symptoms.

“When taking ACV daily, it’s essential not to overdo it and stick with the recommended dose of 1 to 2 tablespoons,” says Melissa Mitri, RD , the New York City-based owner of Melissa Mitri Nutrition. Consuming more than that increases the risk of side effects, like gastrointestinal discomfort, and can affect tooth enamel, she says.

Can I drink apple cider vinegar?

Yes, you can drink apple cider vinegar—cold or hot. Either way, though, it should be diluted with water to cut down on some of the acidity going down your esophagus.

Is it better to drink apple-cider vinegar in the morning or at night?

The ideal timing of taking ACV is debatable. Some schools of thought suggest taking it in the morning can kick-start your day, and others suggest taking it at night may benefit blood sugar most effectively. Ultimately, you should consult with your healthcare provider to determine when you should take your ACV dose.

Another part of this debate is whether to take it before a meal or after. Some claim that it has more benefits when taken on an empty stomach. There is no clear-cut research on this. And some people become nauseated when taking it on an empty stomach. So, again, consult with your healthcare provider about the best timing for you.

What benefits does apple-cider vinegar provide for the body?

While more data is needed to definitively say that ACV offers health benefits, some data suggests that it may help support healthy blood sugar levels, weight-management goals and heart health. It may also have antimicrobial effects.

Does apple-cider vinegar burn belly fat?

Apple-cider vinegar is often marketed as a tool for weight loss, including burning belly fat. While ACV may help you feel fuller and consume fewer calories, the relationship between ACV and fat burning, especially belly fat, has not been proven.

Is there an apple-cider vinegar drink that makes it easier to get down?

Yes! Try our Apple Cider Vinegar Tonic , which combines apple cider vinegar with other healthy ingredients, like green tea, maple syrup and fresh ginger.

Can apple-cider vinegar clean out your liver?

There’s a popular belief that apple-cider vinegar can “cleanse” or “detox” the liver, helping it to function more efficiently. Some proponents of this theory suggest that the acids in ACV can bind to toxins and help the body eliminate them more effectively. However, it’s crucial to mention that such claims are not backed by solid scientific evidence.

The Bottom Line

Apple-cider vinegar is a trendy addition to a healthy diet, with some claims suggesting that ingesting it every day can support healthy blood sugar levels, weight-management goals and more. While many of the health benefits linked to this liquid are based on anecdotal experiences, there is limited but emerging data to support some of these claims.

As long as you get the green light to include apple-cider vinegar in your diet from your health care provider, taking it in appropriate doses comes with little risk, and you may experience health benefits, too.

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What’s it like to be a teacher in america today, public k-12 teachers are stressed about their jobs and few are optimistic about the future of education; many say poverty, absenteeism and mental health are major problems at their school.

Pew Research Center conducted this study to better understand the views and experiences of public K-12 school teachers. The analysis in this report is based on an online survey of 2,531 U.S. public K-12 teachers conducted from Oct. 17 to Nov. 14, 2023. The teachers surveyed are members of RAND’s American Teacher Panel, a nationally representative panel of public K-12 school teachers recruited through MDR Education. Survey data is weighted to state and national teacher characteristics to account for differences in sampling and response to ensure they are representative of the target population.

Here are the questions used for this report , along with responses, and the survey methodology .

Low-poverty , medium-poverty and high-poverty schools are based on the percentage of students eligible for free and reduced-price lunch, as reported by the National Center for Education Statistics (less than 40%, 40%-59% and 60% or more, respectively).

Secondary schools include both middle schools and high schools.

All references to party affiliation include those who lean toward that party. Republicans include those who identify as Republicans and those who say they lean toward the Republican Party. Democrats include those who identify as Democrats and those who say they lean toward the Democratic Party.

Public K-12 schools in the United States face a host of challenges these days – from teacher shortages to the lingering effects of COVID-19 learning loss to political battles over curriculum .

In the midst of all this, teachers express low levels of satisfaction with their jobs. In fact, they’re much less satisfied than U.S. workers overall.

Here’s how public K-12 teachers are feeling about their jobs:

• 77% say their job is frequently stressful.
• 68% say it’s overwhelming.
• 70% say their school is understaffed.
• 52% say they would not advise a young person starting out today to become a teacher.

When it comes to how their students are doing in school, teachers are relatively downbeat about both academic performance and behavior.

Here’s how public K-12 teachers rate academic performance and behavior at their school:

• 48% say the academic performance of most students at their school is fair or poor. A third say it’s good, and only 17% describe it as excellent or very good.
• 49% say the behavior of most students at their school is fair or poor; 35% say it’s good and 13% say it’s excellent or very good.

The COVID-19 pandemic likely compounded these issues. About eight-in-ten teachers (among those who have been teaching for at least a year) say the lasting impact of the pandemic on students’ behavior, academic performance and emotional well-being has been very or somewhat negative.

Assessments of student performance and behavior differ widely by school poverty level. 1 Teachers in high-poverty schools have a much more negative outlook. But feelings of stress and dissatisfaction among teachers are fairly universal, regardless of where they teach.

Related: What Public K-12 Teachers Want Americans To Know About Teaching

As they navigate these challenges, teachers don’t feel they’re getting the support or reinforcement they need from parents.

Majorities of teachers say parents are doing too little when it comes to holding their children accountable if they misbehave in school, helping them with their schoolwork and ensuring their attendance.

Teachers in high- and medium-poverty schools are more likely than those in low-poverty schools to say parents are doing too little in each of these areas.

These findings are based on a survey of 2,531 U.S. public K-12 teachers conducted Oct. 17-Nov. 14, 2023, using the RAND American Teacher Panel. 2 The survey looks at the following aspects of teachers’ experiences:

• Teachers’ job satisfaction (Chapter 1)
• How teachers manage their workload (Chapter 2)
• Problems students are facing at public K-12 schools (Chapter 3)
• Challenges in the classroom (Chapter 4)
• Teachers’ views of parent involvement (Chapter 5)
• Teachers’ views on the state of public K-12 education (Chapter 6)

Problems students are facing

We asked teachers about some of the challenges students at their school are facing. Three problems topped the list:

• Poverty (53% say this is a major problem among students who attend their school)
• Chronic absenteeism (49%)
• Anxiety and depression (48%)

Chronic absenteeism (that is, students missing a substantial number of school days) is a particular challenge at high schools, with 61% of high school teachers saying this is a major problem where they teach. By comparison, 46% of middle school teachers and 43% of elementary school teachers say the same.

Anxiety and depression are viewed as a more serious problem at the secondary school level: 69% of high school teachers and 57% of middle school teachers say this is a major problem among their students, compared with 29% of elementary school teachers.

Fewer teachers (20%) view bullying as a major problem at their school, though the share is significantly higher among middle school teachers (34%).

A look inside the classroom

We also asked teachers how things are going in their classroom and specifically about some of the issues that may get in the way of teaching.

• 47% of teachers say students showing little or no interest in learning is a major problem in their classroom. The share rises to 58% among high school teachers.
• 33% say students being distracted by their cellphones is a major problem. This is particularly an issue for high school teachers, with 72% saying this is a major problem.
• About one-in-five teachers say students getting up and walking around when they’re not supposed to and being disrespectful toward them (21% each) are major problems. Teachers in elementary and middle schools are more likely than those in high schools to see these as challenges.

A majority of teachers (68%) say they’ve experienced verbal abuse from a student – such as being yelled at or threatened. Some 21% say this happens at least a few times a month.

Physical violence is less common. Even so, 40% of teachers say a student has been violent toward them , with 9% saying this happens at least a few times a month.

About two-thirds of teachers (66%) say that the current discipline practices at their school are very or somewhat mild. Only 2% say the discipline practices at their school are very or somewhat harsh, while 31% say they are neither harsh nor mild. Most teachers (67%) say teachers themselves don’t have enough influence in determining discipline practices at their school.

Behavioral issues and mental health challenges

In addition to their teaching duties, a majority of teachers (58%) say they have to address behavioral issues in their classroom every day. About three-in-ten teachers (28%) say they have to help students with mental health challenges daily.

In each of these areas, elementary and middle school teachers are more likely than those at the high school level to say they do these things on a daily basis.

And teachers in high-poverty schools are more likely than those in medium- and low-poverty schools to say they deal with these issues each day.

Cellphone policies and enforcement

Most teachers (82%) say their school or district has policies regarding cellphone use in the classroom.

Of those, 56% say these policies are at least somewhat easy to enforce, 30% say they’re difficult to enforce, and 14% say they’re neither easy nor difficult to enforce.

Experiences with cellphone policies vary widely across school levels. High school teachers (60%) are much more likely than middle school (30%) and elementary school teachers (12%) to say the policies are difficult to enforce (among those who say their school or district has a cellphone policy).

How teachers are experiencing their jobs

Thinking about the various aspects of their jobs, teachers are most satisfied with their relationship with other teachers at their school (71% are extremely or very satisfied).

They’re least satisfied with how much they’re paid – only 15% are extremely or very satisfied with their pay, while 51% are not too or not at all satisfied.

Among teachers who don’t plan to retire or stop working this year, 29% say it’s at least somewhat likely they will look for a new job in the 2023-24 school year. Within that group, 40% say they would look for a job outside of education, 29% say they’d seek a non-teaching job in education, and only 18% say they’d look for a teaching job at another public K-12 school.

Do teachers find their work fulfilling and enjoyable?

Overall, 56% of teachers say they find their job to be fulfilling extremely often or often; 53% say their job is enjoyable. These are significantly lower than the shares who say their job is frequently stressful (77%) or overwhelming (68%).

Positive experiences are more common among newer teachers. Two-thirds of those who’ve been teaching less than six years say their work is fulfilling extremely often or often, and 62% of this group says their work is frequently enjoyable.

Teachers with longer tenures are somewhat less likely to feel this way. For example, 48% of those who’ve been teaching for six to 10 years say their work is frequently enjoyable.

Balancing the workload

Most teachers (84%) say there’s not enough time during their regular work hours to do tasks like grading, lesson planning, paperwork and answering work emails.

Among those who feel this way, 81% say simply having too much work is a major reason.

Many also point to having to spend time helping students outside the classroom, performing non-teaching duties like lunch duty, and covering other teachers’ classrooms as at least minor reasons they don’t have enough time to get all their work done.

A majority of teachers (54%) say it’s very or somewhat difficult for them to balance work and their personal life. About one-in-four (26%) say it’s very or somewhat easy for them to balance these things, and 20% say it’s neither easy nor difficult.

Among teachers, women are more likely than men to say work-life balance is difficult for them (57% vs. 43%). Women teachers are also more likely to say they often find their job stressful or overwhelming.

How teachers view the education system

A large majority of teachers (82%) say the overall state of public K-12 education has gotten worse in the past five years.

And very few are optimistic about the next five years: Only 20% of teachers say public K-12 education will be a lot or somewhat better five years from now. A narrow majority (53%) say it will be worse.

Among teachers who think things have gotten worse in recent years, majorities say the current political climate (60%) and the lasting effects of the COVID-19 pandemic (57%) are major reasons. A sizable share (46%) also point to changes in the availability of funding and resources.

Related:  About half of Americans say public K-12 education is going in the wrong direction

Which political party do teachers trust more to deal with educational challenges?

On balance, more teachers say they trust the Democratic Party than say they trust the Republican Party to do a better job handling key issues facing the K-12 education system. But three-in-ten or more across the following issues say they don’t trust either party:

• Shaping school curriculum (42% say they trust neither party)
• Ensuring teachers have adequate pay and benefits (35%)
• Making schools safer (35%)
• Ensuring adequate funding for schools (33%)
• Ensuring all students have equal access to high-quality K-12 education (31%)

A majority of public K-12 teachers (58%) identify or lean toward the Democratic Party. This is higher than the share among the general public (47%).

• Poverty levels are based on the percentage of students in the school who are eligible for free and reduced-price lunch. ↩
• For details, refer to the Methodology section of the report. ↩
• Urban, suburban and rural schools are based on the location of the school as reported by the National Center for Education Statistics (rural includes town). Definitions match those used by the U.S. Census Bureau. ↩

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Table of contents, ‘back to school’ means anytime from late july to after labor day, depending on where in the u.s. you live, among many u.s. children, reading for fun has become less common, federal data shows, most european students learn english in school, for u.s. teens today, summer means more schooling and less leisure time than in the past, about one-in-six u.s. teachers work second jobs – and not just in the summer, most popular.

About Pew Research Center Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of The Pew Charitable Trusts .

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• v.9(12); 2023 Dec
• PMC10709373

Therapeutic effects of garlic ( Allium sativum ) on female reproductive system: A systematic review

Fatemeh jafari.

a Zanjan Applied Pharmacology Research Center, Zanjan University of Medical Sciences, Zanjan, Iran

b Department of Traditional Medicine, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran

Somayyeh Khalilzadeh

c Department of Traditional Medicine, School of Persian Medicine, Tehran University of Medical Sciences, Tehran, Iran

Fatemeh Nejatbakhsh

d Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran

Maziar Naderie

e Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

Associated Data

The data associated with the study was not deposited into a publicly available repository because no data was used for the research described in the article.

Complementary and alternative medicine, including Persian medicine (PM), offers a variety of disease prevention and treatment methods, including the application of medicinal plants. The health of the reproductive system is an important issue for women, and understanding the potential effect of garlic ( Allium sativum ) for preventive and therapeutic purposes in this field is of interest. This systematic review focused on the effects of garlic on the female reproductive system. The method involved a comprehensive search of relevant literature on experimental animal studies using electronic databases from January 2010 to September 2023, followed by selection of eligible studies and data extraction. A total of 18 studies met the inclusion criteria and were included in the review. This review reported that garlic may have positive effects on women's reproductive health, such as improving hormonal balance, relieving PMS symptoms, and potentially supporting fertility outcomes. This review revealed that garlic compounds such as allicin and ajoene can modulate various aspects of the female reproductive system, including regulation of the menstrual cycle, hormonal balance, fertility, and reproductive disorders. This review determined that further research is needed to elucidate the molecular pathways and direct effects of garlic on the female reproductive system. Although garlic has many potential health benefits, it should not be used as a substitute for medications.

Graphical abstract

1. Introduction

Reproductive health and women's diseases are major challenges in the field of medicine, because these problems affect people's health in different ways and impose a heavy economic burden on societies [ 1 ]. Today, there is a great desire to use complementary and alternative medicine in health-related problems [ 2 , 3 ]. Complementary and alternative medicine, including Persian medicine (PM), proposes a variety of treatment methods, including the use of medicinal plants [ 4 , 5 ]. The use of herbal medicines is one of the important complementary medicine solutions for the prevention and treatment of some diseases around the world [ 6 ]. In PM, different parts of plants such as roots, stems, leaves and flowers are used as herbal medicines [ 4 , 7 , 8 ]. These herbal medicines can be used as extracts or decoctions or in medicinal forms such as tablets and ointments [ 9 ]. PM is generally based on traditional medicine practices, although some of it is supported by scientific research and clinical trials [ 10 ]. PM is commonly used for a wide range of problems, including digestive disorders, respiratory ailments, skin problems, hormonal imbalances, and immune system weakness [ 11 ]. Some of the commonly used herbs used in traditional medicine are: ginger, turmeric, ginseng, chamomile and garlic [ 12 ]. Garlic ( Allium sativum ) has been used in traditional medicine for centuries because of its many health benefits [ 13 ]. It is an edible plant from the Liliaceae family. Garlic has been used as a spice to improve the taste of food since ancient times. Garlic has been studied for a long time due to its medicinal effects in the treatment of various human diseases [ 14 ]. Studies have shown that garlic has many beneficial properties, including antibacterial, antifungal and antiviral effects. Recently, the potential effects of garlic on the reproductive system of women have been noticed [ 15 ]. Garlic has a positive effect on cardiovascular health by reducing blood pressure, reducing cholesterol levels and preventing blood clots [ 16 ]. Furthermore, garlic has antimicrobial properties and can strengthen the immune system. This plant has been traditionally used to prevent and treat colds and flu. In addition, garlic contains compounds that have anti-inflammatory effects that reduce inflammation in the body [ 17 ]. Some studies have shown that garlic may have anti-cancer properties. This plant inhibits the growth of cancer cells to some extent and may have a preventive effect against all types of stomach, intestine and bladder cancers [ 18 ]. Garlic can also improve digestion by stimulating the production of digestive enzymes and the growth of natural intestinal flora. In addition, according to studies, garlic may be effective in reducing the symptoms of digestive disorders such as gastritis and peptic ulcers [ 19 ]. Garlic contains antioxidants that protect the body against oxidative stress and free radical damage that contribute to aging and certain diseases [ 20 ]. The female reproductive system is a complex set of organs that plays an important role in reproduction. It includes structures such as the ovaries, fallopian tubes, uterus, and vagina that work to facilitate menstruation, ovulation, and pregnancy [ 21 ]. Maintaining a healthy reproductive system is very important for mental health and fertility in women. Studies have shown that garlic may have beneficial effects on the female reproductive system [ 22 ]. For example, it has been reported that this plant has antimicrobial properties, which can prevent and treat infections related to external reproductive organs [ 23 ]. Traditionally, garlic has been used to treat vaginal yeast infections. Its antifungal properties can be effective in preventing and reducing such infections. Due to its anti-inflammatory properties, garlic can also reduce inflammation in the reproductive system and relieve symptoms associated with conditions such as endometriosis and pelvic inflammatory disease [ 6 , 24 ]. Some studies have evaluated the effects of garlic on hormone regulation in women. Hormones play an important role in regulating the menstrual cycle and the normal reproductive process [ 25 ]. Studies have reported that garlic may affect certain hormones such as estrogen and progesterone, although more studies are needed to clearly understand these effects [ 26 ]. Moreover, some animal studies have shown that garlic may improve fertility, including increasing the number of viable eggs in female animals. However, in order to reach more definitive results, human clinical trials are needed [ 27 ]. Garlic contains many compounds including various vitamins B2, B6, B1, A and C, a large amount of antioxidants, flavonoids and phenolic and sulfur compounds [ 28 ]. Allicin and ajoene are two biologically active compounds containing garlic sulfur [ 29 ]. Allicin (dialkyl thiosulfinate) plays a key role in the medicinal properties of garlic and is formed by the action of allinase on alliin (S-alkyl-l-cysteine sulfoxide) [ 30 , 31 ]. Allicin and ajoene have been noted for their potential therapeutic effects. It is reported that these compounds have antimicrobial, anti-inflammatory and antioxidant properties. However, limited research has been conducted on their effects on the female reproductive system [ 32 ]. The effects of garlic on hormonal balance, fertility and sexual health have been studied. In a study, Jiao et al. investigated the use of herbal medicines used to treat menstruation in women and the prevalence of menstrual diseases in different regions [ 12 ]. Moreover, Raji et al. evaluated the effects of aqueous garlic extract on some aspects of reproduction in female albino rats (Wistar strain). Their results showed that the aqueous extract of garlic has no harmful effect on the reproductive performance of female rats [ 33 ]. In another study, Wassem et al. carried out a hormonal study on the efficacy of garlic extract in preventing fallopian tube lead acetate toxicity [ 34 ]. Similarly, Bashir et al. conducted a study on the effect of aqueous garlic extract on the changes caused by androgens in the ovaries of female rats before puberty. The results of their study showed that aqueous extract of garlic reduced the number and size of cystic follicles in androgen-treated ovaries of immature rats [ 35 ]. In addition, Musavi et al. reported that the increase in fertility of garlic is probably due to its antioxidant properties [ 29 ]. Most of the researches in this field are preliminary and have been done on animal models on a laboratory scale. More research is needed to better understand the effects of allicin and ajoene on the female reproductive system and their potential therapeutic applications. In addition, individual responses to these compounds may vary and there may be side effects or drug interactions. Garlic is a well-known medicinal plant with food and medicinal uses that has been used in different cultures for years to prevent and treat diseases [ 4 ]. Since the studies conducted in the field of PM have recommended the use of garlic for the prevention and treatment of various diseases, this review can be useful for researchers. In this study, the medicinal effects of garlic on diseases related to the female reproductive system were investigated and interpreted.

2. Methodology

The purpose of this systematic review was to synthesize existing animal studies on the therapeutic effects of garlic on diseases related to the female reproductive system. A systematic search of electronic databases was conducted to identify relevant studies that investigated the effects of garlic compounds on diseases of the female reproductive system. The key questions in the systematic review on the therapeutic effects of garlic on the female reproductive system have been demonstrated in Table 1 . These questions helped guide the systematic review process by providing a clear focus on specific aspects of garlic's therapeutic effects on gynecological diseases. In light of these questions, the aim of this review was to provide a comprehensive synthesis of the available evidence and help understand the potential benefits of garlic in this area.

The questions of this research.

2.1. Study protocol

A protocol was designed to describe the objectives, research questions, and methods used in the systematic review. It defined the methodology, study design, search strategy, inclusion and exclusion criteria, data extraction process, quality assessment, data synthesis, interpretation of results, and reporting. In this protocol, the review was done in a precise and transparent manner [ 36 ].

2.2. Study design

In this study, a qualitative systematic review plan was used, which included the search, selection and systematic analysis of qualitative studies and systematic reviews related to the research topic. These studies were chosen because they investigated the effects of garlic on the function and diseases of the female reproductive system in a laboratory scale and in the form of animal studies. This review followed the guidelines outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [ 36 ].

2.3. Search strategy

The search terms used were “garlic,” “female reproductive system,” “menstruation,” “fertility,” “hormone regulation,” “ovulation,” and “endometrium”. The studies that met specific inclusion criteria were selected for analysis. The review included studies published in English from various databases, such as PubMed, EMBASE, CINAHL, and Scopus from 2010 to 2023. Boolean operators (AND, OR) were also used to enhance search efficacy [ 36 ]. The search strategy in the databases has been showed in Table 2 .

Search strategy in the considered databases.

2.4. Inclusion and exclusion criteria

The inclusion and exclusion criteria for the qualitative systematic review on the effects of garlic on the female reproductive system have been described in Table 3 .

Inclusion and exclusion criteria.

2.5. Data extraction

The information of the articles was reviewed independently by two authors based on the inclusion and exclusion criteria. Finally, both authors classified the data, and in cases where the data were inconsistent, a third author's comments were used. The information obtained from the articles was entered into the checklist according to the quality approval of the articles. The checklist included: name of the author(s), year of publication, study design, sample size, intervention details, results and conclusions.

2.6. Quality assessment

The quality assessment of the included studies was assessed using the SYRCLE risk of bias tool. This tool is designed for animal studies and is the best quality assessment tool in this field. SYRCLE tool consists of ten areas including selection bias, performance bias, diagnosis bias, attrition bias, reporting bias and other sources of bias. This tool is an advanced and improved model of previous quality assessment tools that are specific to animal and preclinical studies, and some of the shortcomings of previous tools related to clinical trials have been corrected [ 37 ].

2.7. Data synthesis

In this study, combined data from included studies were analyzed using thematic analysis. As well as, common themes and patterns related to the effects of garlic on the performance and diseases of the reproductive system of women were identified. The findings were then interpreted to generate meaningful insights and recommendations.

2.8. Interpretation of results

The interpretation of the results included the analysis of the themes identified in relation to the research questions and objectives. The results obtained in the included studies related to the effects of garlic on the reproductive system of women were reviewed. Additionally, final conclusions for health care providers, policy makers, and future research are discussed.

2.9. Reporting

The results of the qualitative systematic review were reported following the guidelines of the PRISMA statement ( Appendix 1 , Appendix 2 ). Recommendations for practice and future research were also included.

3. Results and discussion

A systematic review on the effects of garlic on the female reproductive system was conducted to evaluate the scientific evidence in the available studies. This review collected and analyzed various studies focusing on the effects of garlic compounds on the performance, health and diseases of the female reproductive system. The results of this systematic review showed that garlic compounds have significant effects on the reproductive system of women. A total of 18 studies met the inclusion criteria and were included in this review ( Fig. 1 ). The characteristics of the studies included in this review are described in Table 4 . This review showed that garlic is generally known for its medicinal properties, including anti-inflammatory, antioxidant and antimicrobial properties. Based on the reviewed studies, there is limited scientific evidence about the effects of garlic on the female reproductive system. Garlic is traditionally used as a natural remedy for various women's ailments. The results of this review study showed that garlic has potentially beneficial effects on hormonal regulation, enhancing fertility, regulating the menstrual cycle and reducing inflammation in the female reproductive system [ 38 ]. Some studies have reported that garlic may have beneficial effects on the female reproductive system by reducing menstrual pain and regulating menstrual cycles. However, more research is needed to find out the exact mechanisms. Additionally, some studies have shown the potential benefits of garlic compounds on women's reproductive health. Garlic can help neutralize free radicals because it has no side effects and also contains flavonoids, vitamins, and fructose and sulfur compounds [ 39 ]. Several bioactive compounds in garlic, including allicin and diallyl sulfide, are thought to be responsible for promoting reproductive health. These compounds may modulate hormone levels and have anti-inflammatory and antioxidant activities. As a result, they affect various aspects of the female reproductive system. When fresh garlic is crushed, alliin is converted to allicin by allinase [ 40 ]. The produced allicin is unstable and rapidly hydrolyzes to other sulfur-containing compounds such as diallyl disulfide, diallyl trisulfide (DAT), and diallyl tetrasulfide. Diallyl trisulfide has the highest abundance (45 %) among the organic sulfur compounds found in garlic and has potential medicinal functions [ 41 ]. This review showed that most of the reviewed studies were at high risk of bias ( Table 5 ). In most of these studies, randomization in sampling and research blinding were not clearly mentioned. Among the 10 reviewed studies, garlic extract was given to animals in the form of raw plant and powder. In these studies, the maximum and minimum sample sizes were 62 and 10 mice, which were investigated in experimental studies [ 42 ]. The control group received distilled water, normal saline, and powder containing starch, and the treatment group received garlic extract, adriamycin, titanium dioxide, garlic oil, N-acetylsicine, vitamin E, cadmium, cooked garlic, and garlic juice [ 29 ].

Trend of screening and choosing articles based on PRISMA guidelines.

Characteristics of included studies in the review research.

Risk of bias for animal studies, using the SYRCLE risk of bias tool.

3.1. Preparation of garlic extract for therapeutic purposes

The garlic plant has unique medicinal properties that can be used through extract preparation. This extract is rich in bioactive compounds that are responsible for its various therapeutic properties. To prepare garlic extract for therapeutic purposes, fresh and high-quality cloves of garlic should be selected first, and then the outer skin should be removed. Peeled garlic cloves should be crushed or crushed to make them into small pieces. Crushing or crushing garlic helps release its beneficial compounds. Then chopped or crushed garlic is poured into the container and a suitable solvent is added to extract its active compounds. Common solvents for extracting garlic compounds are alcohol or a mixture of alcohol and water. In the next step, the glass container is closed with a tight lid and it is kept in a cool and dark place away from direct sunlight. It is necessary to soak the garlic for a certain period of time, usually 2–4 weeks. During this time, the mixture should be gently stirred every few days to ensure a better extraction process. Afterwards, after the soaking period, the mixture is strained using cheesecloth, a fine mesh strainer, or a coffee filter to remove solid particles. The garlic solids are pressed in the cheese cloth until the juice is completely removed. In the next step, the strained liquid is poured into a dark glass bottle or vial with a closed cap. Light-sensitive compounds in garlic are degraded when exposed to light, so it is important to store the extract in a dark container. It is better to record the date of preparation and the concentration of the extract on the bottle with a label. Then the garlic extract is stored in the refrigerator to maintain its properties and freshness. It can usually be kept for several months, but it is essential that the extract be checked regularly for signs of spoilage and discarded if there is any change in color, smell or texture [ 58 ]. In addition, to treat genital problems, garlic bulbs are completely peeled, washed and chopped into small pieces. Then 250 g of chopped garlic is dissolved in distilled water and kept in the refrigerator for 12 h. To prepare the aqueous extract of garlic, 100 g of garlic are homogenized in 250 ml of distilled water. After filtration with Whatman No. 1 filter paper (0.45 μm), 1 ml of this fresh solution per 100 g of body weight, equivalent to 0.4 g of active ingredient per 100 g of body weight, is used orally [ 59 ].

3.2. Antimicrobial properties

In this review, one of the key results was that garlic has antimicrobial properties that can be effective in fighting various infections that can affect the reproductive system, such as yeast infections and bacterial vaginosis [ 60 ]. However, more research is needed to establish the exact mechanism of action and effectiveness of garlic in prevention or treatment through its antimicrobial properties [ 6 ]. Garlic has traditionally been valued for its antimicrobial properties and can be effective in healing various infections. Garlic has strong antimicrobial properties against a wide range of bacteria, viruses, fungi and parasites. Garlic may be effective in treating female genital tract infections, including infections caused by Candida albicans , a common cause of vaginal yeast infections. Some studies have also shown that garlic may have antimicrobial effects against the bacteria responsible for urinary tract infections [ 61 ]. Garlic has been surveyed for its potential role in the prevention and treatment of urinary tract infections (UTIs), which commonly affect women. However, more studies need to be done to confirm this and determine effective doses. In addition, garlic has antifungal properties and can be used in the treatment of fungal infections such as vaginal yeast infections [ 62 ]. According to the review and interpretation of the studies included in this review, garlic extract and garlic oil showed inhibitory effects on Candida species. However, careful research should be done to determine its dosage in the treatment of fungal infections. Garlic contains active ingredients allicin and ajoene , which have strong antimicrobial effects. These compounds are the main factors in the treatment of female genital tract infection, which can be extracted from the garlic plant and used in capsule and ointment forms [ 63 ].

3.3. Anti-inflammatory properties

This review also found that garlic compounds have anti-inflammatory properties. Inflammation is a common factor in several reproductive disorders such as endometriosis, pelvic inflammatory disease (PID), polycystic ovary syndrome (PCOS), chronic pelvic pain, and ovarian cysts [ 64 ]. The anti-inflammatory effects of garlic may be effective in reducing some of the symptoms associated with these disorders, although more specific studies on the reproductive system are needed [ 65 ]. Arreola et al. conducted a review study on the immune system modulating and anti-inflammatory effects of garlic compounds. The results obtained from their experimental study showed that garlic modulates the function by stimulating certain types of cells, such as macrophages, lymphocytes, natural killer (NK) cells, dendritic cells and eosinophils with mechanisms such as modulation of cytokine secretion, immunoglobulin production and phagocytosis [ 17 ]. Since the dysfunction of the immune system plays an important role in the development and progression of many diseases, several studies were conducted on the use of garlic extract and compounds in the field of immune system modulation. Analysis of the results of these studies showed that the anti-inflammatory activity of garlic is due to the presence of sulfur compounds allicin and ajoene . Moreover, this review showed that garlic extract modulates cytokine secretion and such modulation can reduce inflammatory manifestations, especially in female reproductive system disorders.

3.4. Antioxidant properties

This review showed that garlic extract also has antioxidant activity that may protect against reproductive disorders associated with oxidative stress [ 66 ]. In addition to sulfur compounds, garlic also has antioxidant compounds and can increase fertility by reducing lipid peroxidation. However, more research is needed to find out the mechanism of action, dosage and long-term safety considerations [ 67 ]. Cherry et al. carried out a study on garlic and fertility. Although their study looked at the effects of garlic on male fertility, it also briefly mentioned the potential benefits of garlic on female fertility. Garlic has antioxidant properties that protect eggs from oxidative stress and improve their quality, potentially increasing fertility [ 68 ]. Mostafa et al. conducted a study on the antioxidant effect of garlic ( Allium sativum ) and black seed ( Nigella sativa ) in healthy postmenopausal women. 30 healthy postmenopausal women (mean age 50.31 ± 4.23 years) participated in this study. They took two garlic softgels (each equivalent to 1000 mg of fresh garlic cloves) and raw ground black seed powder at a dose of 3 g per day for 8 weeks. In their study, the oxidizing activity of malondialdehyde in plasma and the activity of antioxidants superoxide dismutase and glutathione peroxidase in red blood cells were investigated [ 69 ]. The results of their study showed that significant low levels of plasma malondialdehyde were observed along with increased activity of glutathione peroxidase and superoxide dismutase. From their study, it was concluded that menopause is related to the increase of oxidative stress and the decrease of some antioxidant parameters. The consumption of raw garlic and its extract may have a positive effect on improving the balance between blood oxidants and antioxidants in healthy postmenopausal women [ 69 ]. This review showed that the antioxidant properties of garlic may protect ovum and reproductive organs from oxidative damage and reduce the risk of infertility [ 70 ]. Asadpour et al. reported that garlic has antioxidant activity and prevents the activity of oxygen peroxide due to the presence of vitamin E in garlic extract [ 71 ]. Garlic compounds such as allicin and ajoene have antioxidant properties. These antioxidants can protect cells from oxidative damage and potentially reduce the risk of reproductive disorders. In addition, reactive oxygen species present in garlic extract play a very important role in intracellular signaling processes. Reactive oxygen species play a significant role in infertility due to excessive production of oxidants and thus reducing the ability of the reproductive system's antioxidant system [ 72 ].

3.5. Hormonal regulation

The results of included studies showed that garlic compounds have potential effects on menstrual cycle regulation, hormonal regulation and fertility. However, some studies also reported adverse effects, such as changes in endometrial thickness and hormonal changes [ 25 , 73 ]. This review showed that garlic plays a role in reducing menstrual pain and improving menstrual regularity. Garlic has analgesic properties that are effective in relieving menstrual pain. In addition, evidence from the reviewed studies showed that regular consumption of garlic was correlated with menstrual cycle regularity, indicating garlic's potential role in hormonal regulation. Based on an analysis of studies, garlic may have modulating effects on estrogen levels in the body, which could potentially affect the female reproductive system [ 74 , 75 ]. Some studies have shown that certain compounds in garlic have estrogen-like properties and help regulate hormone levels. Some studies also report that garlic may play a role in modulating hormone levels, especially estrogen. Garlic can be effective in regulating menstrual cycles or reducing the symptoms of diseases such as polycystic ovary syndrome (PCOS) [ 76 ]. However, the evidence is limited and more laboratory studies are needed to draw firm conclusions. Several studies have shown that garlic may have a positive effect on the regulation of female hormones. Examining the effects of garlic extract on the reproductive potential of female rats by Nazifi et al. demonstrated that the administration of garlic extract for 14 days significantly changed the serum levels of estradiol and progesterone to normal levels, which indicates the potential positive effect of garlic on the secretion and Regulation of hormones. Garlic supplementation has been shown to reduce estrogen, progesterone, and luteinizing hormone (LH) levels, thereby reducing the hormonal imbalances that commonly occur in PCOS. Garlic has been found to contain compounds such as allicin , which may help regulate estrogen levels [ 73 , 77 , 78 ]. Modaresi et al. reported that garlic can increase the secretion of estrogen and progesterone blood levels in women. This action occurs with the formation of more follicles [ 79 , 80 ]. Hammami et al. concluded that garlic contains phytoestrogens that have a direct effect on estrogen levels [ 81 ]. Additionally, Oi et al.'s results showed that garlic supplementation increases LH from the pituitary gland, which stimulates the release of estrogen and progesterone [ 82 ]. Ahmadian et al. investigated the effect of garlic tablets on protein oxidation biomarkers in postmenopausal women with osteoporosis. This study was a double-blind randomized clinical trial that was conducted on 42 postmenopausal women in Yazd during 2013–2014. Women with osteoporosis were randomly assigned to two garlic groups (GG) and placebo group (PG). GG participants took two garlic tablets daily for 1 month, and PG participants took placebo tablets in the same manner. After 30 days, plasma levels of carbonyl groups (PCO), total antioxidant capacity (TAC) and advanced oxidation protein products (AOPPs) were analyzed by spectrophotometric assay. The results of their study showed that garlic tablets reduced PCO plasma levels. According to the results obtained from their study, the parameters of the placebo group before and after the study did not show any significant difference. Moreover, the level of MDA before taking the drug was also reduced compared to before in the garlic group [ 83 ]. This study indicated that garlic tablets had decreased PCO plasma levels (47.37 ± 5.98 vs. 19.62 ± 3.40 nM, p ≤ 0.001, before and after the study, respectively), AOPPs (738.95 ± 151.86 vs. 585.12 ± 209.99 μM, p ≤ 0.008, before and after the study, respectively), and increased TAC (11.34 ± 10.80 vs. 47.93 ± 17.80, p ≤ 0.001, before and after the study, respectively). The levels of MDA before taking the drug in comparison to before Garlic group was also reduced (1.30 ± 1.04 vs. 0.92 ± 0.81 μM, p = 0.01, before and after the study, respectively) [ 83 ]. In another study Jafari et al. surveyed the effect of garlic supplementation on premenstrual disorders. The results of their study showed that there was no statistically significant difference between the two groups of premenstrual symptoms before the intervention. After treatment with garlic for three consecutive cycles, the total score of the severity of premenstrual symptoms significantly reduced from 34.09 ± 7.31 to 11.21 ± 7.17. In the placebo group, this score changed from 33.35 ± 7.96 to 24.28 ± 7.22. The difference between mean changes in the two groups was 13.78, with a 95 % Confidence Interval (CI) of 11.23–16.33. Besides, no serious side effects were observed in these two study groups. The results of their study showed that the consumption of garlic can be considered as a complementary treatment in the prevention and treatment of premenstrual disorders [ 84 ]. Additionally, this review identified and reviewed some studies that reported compounds in garlic may have contraceptive properties. However, these findings are limited and more research is needed to confirm such claims. According to the selected studies, the effects of garlic on breastfeeding have not been well studied. There is no conclusive evidence that garlic has a negative effect on breastfeeding. Although some studies have reported that garlic may change the taste or smell of breast milk, potentially affecting infant feeding behavior.

3.6. Fertility and reproductive health

This review found that garlic may have positive effects on women's fertility and reproductive health. Garlic contains antioxidants such as selenium and vitamin C, which may protect the ovum from oxidative damage. Shah et al. investigated the capacity of diallyl trisulfide (DAT) to reduce the fertility of Sitotroga cerealella . The results of their study showed that DAT negatively regulated the fertility of S. cerealella [ 85 ]. Raji et al. evaluated the effect of garlic extract on some aspects of reproduction in female albino rats (Wistar strain). In their study, there was a significant increase in the length of the right uterine horn and a decrease in the length of the left uterine horn (P < 0.05) in groups B, C, D and E compared to group A. In addition, a significant difference (p > 0.05) was reported in pregnant women without abortion in infant size, live birth weight and infant mortality among the groups. These results showed that the aqueous extract of garlic had no harmful effect on the reproductive performance of female mice [ 33 ]. A review of several studies showed that garlic has a beneficial effect on ovarian activity and plays an important role in improving women's reproductive outcomes. Garlic affects the hypothalamus-pituitary function due to its diallyl disulfide compound. Garlic can also increase fertility possibly due to its antioxidant properties. However, clinical trials are needed to investigate these mechanisms in detail [ 86 ].

3.7. Menstruation and menstrual pain

In this review, it was found that garlic has cardiovascular benefits, including lowering cholesterol levels and lowering blood pressure. These effects may indirectly benefit the female reproductive system with better blood flow in the pelvic area, which is essential for healthy menstrual cycles and overall reproductive health. Faroughi et al. studied the effects of garlic extract on the symptoms of premenstrual syndrome (PMS) in a double-blind randomized clinical trial with placebo. The results of their study showed that garlic supplementation significantly reduced the severity of PMS symptoms. They concluded from this study that garlic may have positive effects on menstrual disorders and mood swings in women [ 87 ]. By affecting the anterior pituitary gland, diallyl disulfide stimulates basophil cells and the secretion of sex hormones LH. It is important to note that the effects of garlic on the female reproductive system and hormonal regulation are still being investigated and more research is needed to develop a clear understanding of these effects. While garlic can be a healthy addition to a balanced diet, it's always best to consult your doctor before making any significant changes to your diet because the compound allicin may have vasodilating effects [ 88 ]. This feature can dilate blood vessels and improve blood flow. Garlic has traditionally been used to help regulate menstruation and reduce menstrual pain. The herb is believed to have properties that can stimulate the uterus and promote blood flow, which may help regulate irregular periods. However, scientific evidence to support these claims is limited and more research is needed to confirm these effects.

3.8. Anticancer properties

A review of these studies showed that garlic may have anticancer effects in certain types of cancer, including breast, ovarian, and cervical cancer. Garlic contains compounds such as allicin , which have been shown to inhibit the growth of cancer cells, reduce tumor size, and induce apoptosis in cancer cells. However, more research is needed to determine the specific effects of garlic on different types of cancer [ 89 ]. Garlic is rich in antioxidants and anti-inflammatory compounds that may have positive effects on overall health, including the female reproductive system. Chronic inflammation and oxidative stress can cause the development of cancer [ 90 ]. By reducing inflammation and oxidative stress, garlic may help protect cells from damage. In several studies, the ability of garlic extract to inhibit the growth and progression of bladder cancer has been mentioned [ 91 ]. Garlic's ability to inhibit cancer growth is based on preventing tumor angiogenesis and stimulating helper T cells. Garlic has a positive effect on the immune system and reduces the progress of cancer. According to a review of these studies, garlic has shown strong anticancer activity, especially in relation to tumors of the digestive tract [ 92 ]. Furthermore, according to these included studies, garlic consumption reduces the risk of esophageal, stomach, and colon cancer. Several bioactive compounds in garlic, including DATS, allicin , DADS, diallyl sulfide, and allyl mercaptan, have anticancer properties [ 93 ]. It is important to note that although garlic is promising in some areas, it is not a definitive cure for cancer. There are limited studies on the specific effects of garlic on female genital cancers [ 94 ]. However, due to its potential anticancer properties, garlic can have a favorable effect on the prevention and progression of cancers of the female reproductive system.

3.9. Garlic effects in Persian medicine (PM)

Garlic is known as a valuable medicinal plant in Persian medicine (PM) with various health benefits. For centuries, this plant has been used in traditional Iranian medicine to treat various diseases. Today, people are more inclined to use complementary and alternative medicine (CAM) for premenstrual disorder (PMD) due to side effects and drug interactions [ 95 ]. PM as a CAM method suggests appropriate approaches. Among the various CAM methods, the use of herbal medicines is the most popular method. According to sources of Iranian medicine, garlic is suggested as one of the herbal medicines that can be effective in PMS by reducing blood viscosity and regulating menstruation [ 84 ]. The mechanism of garlic's effectiveness is not fully understood, but a number of studies have reported that garlic dilutes the blood and reduces blood clotting time [ 96 ]. Therefore, it can facilitate the menstrual process. Various PM-related studies have investigated the various uses of garlic in fertility-related problems, including menstrual regulation, prevention, and treatment of menstrual retention [ 97 ]. In these studies, the various uses of garlic in the treatment of infertility as well as the prevention and treatment of histrionic diseases have been mentioned [ 98 ]. Therefore, if there is sufficient clinical evidence, garlic can be prescribed as a medicinal supplement in the prevention and treatment of female reproductive diseases along with drugs [ 84 ].

3.10. Strengths and weaknesses of the systematic review

3.10.1. strengths.

This systematic review followed a robust research methodology, ensuring that no relevant studies were overlooked. This method helped minimize bias and provided a comprehensive understanding of the subject. In addition, this review included a wide range of animal experiments as well as laboratory experiments. This increased accuracy and specificity in this field. The review specified clear inclusion and exclusion criteria, and only studies that met certain quality standards were included. This strengthened the validity of the survey results. The review also critically assessed the quality of the included studies, assessing factors such as study design, sample size, and statistical analysis. This evaluation increased the validity of the findings and results of the review. Finally, this review provided a summary of the main findings of the included studies. It helps readers quickly understand the key concepts and implications of garlic's therapeutic effects on the female reproductive system.

3.10.2. Weaknesses

This review included studies with different methodologies, which made comparison and synthesis of results challenging. This heterogeneity may have weakened the strength of the review's overall conclusions. Besides, a number of studies included in this review focused on short-term effects, which may limit the review's ability to assess the long-term therapeutic benefits of garlic. Long-term studies will provide a more comprehensive understanding of the sustainability and potential risks associated with the consumption of garlic.

3.10.3. Future perspective

Despite the promising results, the available literature on the therapeutic effects of garlic on the female reproductive system is limited and heterogeneous in terms of study design, sample size, and methodology. More research is needed to provide stronger evidence and establish mechanisms of action for the beneficial effects of garlic. Future studies should consider randomized controlled trials with larger sample sizes and long-term follow-ups to evaluate the efficacy, safety, and possible side effects of garlic supplementation. In addition, investigating the active components of garlic and its specific action mechanisms will help to better understand its therapeutic effects.

4. Conclusions

Garlic plant ( Allium sativum ) has been considered for centuries because of its taste characteristics and therapeutic effects. In recent years, the therapeutic effects of garlic on the function and disorders of the female reproductive system have been discussed. According to this systematic review, garlic had several therapeutic effects on the female reproductive system. Garlic has been found to have antimicrobial activity against various pathogens such as Candida albicans that affect the female reproductive system. Thus, the plant may be effective in preventing or treating infections, including vaginal yeast infections and urinary tract infections. Garlic has anti-inflammatory properties that may reduce inflammation in the reproductive system. This can be effective for women with diseases such as pelvic inflammatory disease or endometriosis, where inflammation plays an important role. Some studies have demonstrated that garlic may affect hormonal balance. Additionally, garlic has been found to regulate estrogen levels and can potentially improve conditions associated with hormonal imbalances, such as polycystic ovary syndrome (PCOS). Garlic contains various antioxidants that can protect cells from damage caused by oxidative stress. This antioxidant activity has positive effects on the reproductive system by reducing oxidative damage. Furthermore, garlic consumption can reduce menopausal symptoms such as hot flashes and mood swings. More research is needed to confirm this correlation and determine the mechanisms of these effects. Although some animal studies have shown that garlic may increase fertility, there is currently limited evidence of its direct effect on female fertility. Overall, the reviewed studies showed that garlic may have therapeutic effects on the female reproductive system. Garlic shows antimicrobial, anti-inflammatory, hormonal balance and antioxidant properties that can promote reproductive health. However, further research, especially in human trials, is needed to confirm these findings and determine optimal dosage and administration methods.

Ethics statement

Not applicable.

Funding statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Additional information

No additional information is available for this paper.

Data availability statement

Credit authorship contribution statement.

Fatemeh Jafari: Methodology, Conceptualization. Somayyeh Khalilzadeh: Supervision. Fatemeh Nejatbakhsh: Writing – review & editing, Maziar Naderi, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Appendix 1. 

Prisma_2020_checklist.

From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021; 372:n71. https://doi.org/10.1136/bmj.n71 .

Appendix 2. 

Prisma_2020_abstract_checklist.

From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al. The PRISMA 2020 statement: an updated guideline for reporting systematic.

Reviews: BMJ 2021; 372:n71. https://doi.org/10.1136/bmj.n71 .