research study on food

Fruits, vegetables, and health: A comprehensive narrative, umbrella review of the science and recommendations for enhanced public policy to improve intake

Affiliations.

• 1 Department of Nutrition and Food Studies, George Mason University, Fairfax, Virginia, USA.
• 2 Think Healthy Group, Inc., Washington, DC, USA.
• 3 Department of Nutrition Science, Purdue University, West Lafayette, Indiana, USA.
• 4 Friedman School of Nutrition Science and Policy, Tufts University, Boston, Massachusetts, USA.
• 5 Center for Nutrition Research, Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, Illinois, USA.
• 6 Biofortis Research, Merieux NutriSciences, Addison, Illinois, USA.
• 7 Department of Human Nutrition, University of Alabama, Tuscaloosa, Alabama, USA.
• 8 Department of Epidemiology, University of Washington, Seattle, Washington, USA.
• 9 School of Exercise and Nutritional Sciences, San Diego State University, San Diego, California, USA.
• 10 Bone and Body Composition Laboratory, College of Family and Consumer Sciences, University of Georgia, Athens, Georgia, USA.
• 11 College of Education and Human Ecology, The Ohio State University, Columbus, Ohio, USA.
• 12 Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey, USA.
• 13 D&V Systematic Evidence Review, Bronx, New York, USA.
• PMID: 31267783
• DOI: 10.1080/10408398.2019.1632258

Fruit and vegetables (F&V) have been a cornerstone of healthy dietary recommendations; the 2015-2020 U.S. Dietary Guidelines for Americans recommend that F&V constitute one-half of the plate at each meal. F&V include a diverse collection of plant foods that vary in their energy, nutrient, and dietary bioactive contents. F&V have potential health-promoting effects beyond providing basic nutrition needs in humans, including their role in reducing inflammation and their potential preventive effects on various chronic disease states leading to decreases in years lost due to premature mortality and years lived with disability/morbidity. Current global intakes of F&V are well below recommendations. Given the importance of F&V for health, public policies that promote dietary interventions to help increase F&V intake are warranted. This externally commissioned expert comprehensive narrative, umbrella review summarizes up-to-date clinical and observational evidence on current intakes of F&V, discusses the available evidence on the potential health benefits of F&V, and offers implementation strategies to help ensure that public health messaging is reflective of current science. This review demonstrates that F&V provide benefits beyond helping to achieve basic nutrient requirements in humans. The scientific evidence for providing public health recommendations to increase F&V consumption for prevention of disease is strong. Current evidence suggests that F&V have the strongest effects in relation to prevention of CVDs, noting a nonlinear threshold effect of 800 g per day (i.e., about 5 servings a day). A growing body of clinical evidence (mostly small RCTs) demonstrates effects of specific F&V on certain chronic disease states; however, more research on the role of individual F&V for specific disease prevention strategies is still needed in many areas. Data from the systematic reviews and mostly observational studies cited in this report also support intake of certain types of F&V, particularly cruciferous vegetables, dark-green leafy vegetables, citrus fruits, and dark-colored berries, which have superior effects on biomarkers, surrogate endpoints, and outcomes of chronic disease.

Keywords: Fruit; health; nutrition; produce; vegetable.

Publication types

• Diet, Healthy*
• Nutrition Policy*
• Observational Studies as Topic
• Systematic Reviews as Topic
• United States
• Vegetables*

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• 25 Jan 2021
• Working Paper Summaries

India’s Food Supply Chain During the Pandemic

Policy makers in the developing world face important tradeoffs in reacting to a pandemic. The quick and complete recovery of India’s food supply chain suggests that strict lockdown measures at the onset of pandemics need not cause long-term economic damage.

• 08 Jun 2020

Food Security and Human Mobility During the Covid-19 Lockdown

COVID-19 represents not only a health crisis but a crisis of food insecurity and starvation for migrants. Central governments should ensure that food security policies are implemented effectively and engage with local governments and local stakeholders to distribute food to migrants in the immediate term.

• 29 May 2020

How Leaders Are Fighting Food Insecurity on Three Continents

The pandemic could almost double the number of people facing food crises in lower-income populations by the end of 2020. Howard Stevenson and Shirley Spence show how organizations are responding. Open for comment; 0 Comments.

• 31 Jan 2019
• Cold Call Podcast

How Wegmans Became a Leader in Improving Food Safety

Ray Goldberg discusses how the CEO of the Wegmans grocery chain faced a food safety issue and then helped the industry become more proactive. Open for comment; 0 Comments.

• 15 Nov 2018

Can the Global Food Industry Overcome Public Distrust?

The public is losing trust in many institutions involved in putting food on our table, says Ray A. Goldberg, author of the new book Food Citizenship. Here's what needs to be done. Open for comment; 0 Comments.

• 15 Mar 2018

Targeted Price Controls on Supermarket Products

Governments sometimes consider targeted price controls when popular goods become less affordable. Looking at price controls in Argentina between 2007 and 2015, this study’s findings suggest that new technologies like mobile phones are allowing governments to better enforce targeted price control programs, but the impact of these policies on aggregate inflation is small and short-lived.

• 26 Jun 2017
• Research & Ideas

How Cellophane Changed the Way We Shop for Food

Research by Ai Hisano exposes cellophane's key role in developing self-service merchandising in American grocery stores, and how its manufacturers tried to control the narrative of how women buy food. Open for comment; 0 Comments.

• 31 May 2017
• Sharpening Your Skills

10 Harvard Business School Research Stories That Will Make Your Mouth Water

The food industry is under intense study at Harvard Business School. This story sampler looks at issues including restaurant marketing, chefs as CEOs, and the business of food science. Open for comment; 0 Comments.

• 18 Nov 2016

Standardized Color in the Food Industry: The Co-Creation of the Food Coloring Business in the United States, 1870–1940

Beginning in the late 19th century, US food manufacturers tried to create the “right” color of foods that many consumers would recognize and in time take for granted. The United States became a leading country in the food coloring business with the rise of extensive mass marketing. By 1938, when Congress enacted the Food, Drug, and Cosmetic Act, the food coloring business had become a central and permanent component of food marketing strategies. This paper shows how food manufacturers, dye makers, and regulators co-created the food coloring business. Food-coloring practices became integrated into an entire strategy of manufacturing and marketing in the food industry.

• 16 May 2016

Food Safety Economics: The Cost of a Sick Customer

When restaurants source from local growers, it can be more difficult to assess product safety—just another wrinkle in high-stakes efforts to keep our food from harming us. Just ask Chipotle. John A. Quelch discusses a recent case study on food testing. Open for comment; 0 Comments.

• 15 May 2007

I’ll Have the Ice Cream Soon and the Vegetables Later: Decreasing Impatience over Time in Online Grocery Orders

How do people’s preferences differ when they make choices for the near term versus the more distant future? Providing evidence from a field study of an online grocer, this research shows that people act as if they will be increasingly virtuous the further into the future they project. Researchers examined how the length of delay between when an online grocery order is completed and when it is delivered affects what consumers order. They find that consumers purchase more "should" (healthy) groceries such as vegetables and less "want" (unhealthy) groceries such as ice cream the greater the delay between order completion and order delivery. The results have implications for public policy, supply chain managers, and models of time discounting. Key concepts include: Consumers spend less and order a higher percentage of "should" items and a lower percentage of "want" items the further in advance of delivery they place a grocery order. Encouraging people to order their groceries up to 5 days in advance of consumption could influence the healthfulness of the foods that people consume. Similarly, asking students in schools to select their lunches up to a week in advance could considerably increase the healthfulness of the foods they elect to eat. Online and catalog retailers that offer a range of goods as well as different delivery options might be able to improve their demand forecasting by understanding these findings. Closed for comment; 0 Comments.

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News Release

Thursday, May 16, 2019

NIH study finds heavily processed foods cause overeating and weight gain

Small-scale trial is the first randomized, controlled research of its kind.

People eating ultra-processed foods ate more calories and gained more weight than when they ate a minimally processed diet, according to results from a National Institutes of Health study. The difference occurred even though meals provided to the volunteers in both the ultra-processed and minimally processed diets had the same number of calories and macronutrients. The results were published in Cell Metabolism .

This small-scale study of 20 adult volunteers, conducted by researchers at the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), is the first randomized controlled trial examining the effects of ultra-processed foods as defined by the NOVA classification system . This system considers foods “ultra-processed” if they have ingredients predominantly found in industrial food manufacturing, such as hydrogenated oils, high-fructose corn syrup, flavoring agents, and emulsifiers.

Previous observational studies looking at large groups of people had shown associations between diets high in processed foods and health problems. But, because none of the past studies randomly assigned people to eat specific foods and then measured the results, scientists could not say for sure whether the processed foods were a problem on their own, or whether people eating them had health problems for other reasons, such as a lack of access to fresh foods.

“Though we examined a small group, results from this tightly controlled experiment showed a clear and consistent difference between the two diets,” said Kevin D. Hall, Ph.D., an NIDDK senior investigator and the study’s lead author. “This is the first study to demonstrate causality — that ultra-processed foods cause people to eat too many calories and gain weight.”

For the study, researchers admitted 20 healthy adult volunteers, 10 male and 10 female, to the NIH Clinical Center for one continuous month and, in random order for two weeks on each diet, provided them with meals made up of ultra-processed foods or meals of minimally processed foods. For example, an ultra-processed breakfast might consist of a bagel with cream cheese and turkey bacon, while the unprocessed breakfast was oatmeal with bananas, walnuts, and skim milk.

The ultra-processed and unprocessed meals had the same amounts of calories, sugars, fiber, fat, and carbohydrates, and participants could eat as much or as little as they wanted.

On the ultra-processed diet, people ate about 500 calories more per day than they did on the unprocessed diet. They also ate faster on the ultra-processed diet and gained weight, whereas they lost weight on the unprocessed diet. Participants, on average, gained 0.9 kilograms, or 2 pounds, while they were on the ultra-processed diet and lost an equivalent amount on the unprocessed diet.

“We need to figure out what specific aspect of the ultra-processed foods affected people’s eating behavior and led them to gain weight,” Hall said. “The next step is to design similar studies with a reformulated ultra-processed diet to see if the changes can make the diet effect on calorie intake and body weight disappear.”

For example, slight differences in protein levels between the ultra-processed and unprocessed diets in this study could potentially explain as much as half the difference in calorie intake.

“Over time, extra calories add up, and that extra weight can lead to serious health conditions,” said NIDDK Director Griffin P. Rodgers, M.D. “Research like this is an important part of understanding the role of nutrition in health and may also help people identify foods that are both nutritious and accessible — helping people stay healthy for the long term.”

While the study reinforces the benefits of unprocessed foods, researchers note that ultra-processed foods can be difficult to restrict. “We have to be mindful that it takes more time and more money to prepare less-processed foods,” Hall said. “Just telling people to eat healthier may not be effective for some people without improved access to healthy foods.”

Support for the study primarily came from the NIDDK Division of Intramural Research.

About the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): The NIDDK, a component of the National Institutes of Health (NIH), conducts and supports research on diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition and obesity; and kidney, urologic and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe, and disabling conditions affecting Americans. For more information about the NIDDK and its programs, see https://www.niddk.nih.gov .

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov .

NIH…Turning Discovery Into Health ®

Hall KD, et al. Ultra-processed diets cause excess calorie intake and weight gain: A one-month inpatient randomized controlled trial of ad libitum food intake. Cell Metabolism . May 16, 2019.

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Watch CBS News

Limit these ultra-processed foods for longer-term health, 30-year study suggests

By Sara Moniuszko

Edited By Paula Cohen

Updated on: May 10, 2024 / 11:09 AM EDT / CBS News

New research is adding to the evidence linking  ultra-processed foods  to health concerns. The study tracked people's habits over 30 years and found those who reported eating more of certain ultra-processed foods had a slightly higher risk of death — with four categories of foods found to be the biggest culprits. 

For the study, published in The BMJ , researchers analyzed data on more than 100,000 U.S. adults with no history of cancer, cardiovascular disease or diabetes. Every four years between 1986 and 2018, the participants completed a detailed food questionnaire.

The data showed those who ate the most  ultra-processed food — about 7 servings per day — had a 4% higher risk of death by any cause, compared to participants who ate the lowest amount, a median of about 3 servings per day.

Ultra-processed foods include "packaged baked goods and snacks, fizzy drinks, sugary cereals, and ready-to-eat or heat products,"  a news release  for the study noted. "They often contain colors, emulsifiers, flavors, and other additives and are typically high in energy, added sugar, saturated fat, and salt, but lack vitamins and fiber."

Foods with the strongest associations with increased mortality, according to the study, included:

• Ready-to-eat meat, poultry and seafood-based products
• Sugary drinks
• Dairy-based desserts
• Highly processed breakfast foods

Ultra-processed food is a "very mixed group of very different foods," the lead author of the study, Mingyang Song,  told CBS News , meaning these categories can offer a helpful distinction. 

"Some of the foods actually have really beneficial ingredients like vitamins, minerals, so that's why we always recommend that people not focus too much on the (whole of) ultra-processed food, but rather the individual categories of ultra-processed food."

The research included a large number of participants over a long timespan, but it did have some limitations. As an observational study, no exact cause-and-effect conclusions can be drawn. And the participants were health professionals and predominantly White and non-Hispanic, "limiting the generalizability of our findings," the authors acknowledged.

But they wrote that the findings "provide support for limiting consumption of certain types of ultra-processed food for long term health." 

"Future studies are warranted to improve the classification of ultra-processed foods and confirm our findings in other populations," they added.

This study comes after other research published earlier this year found diets high in ultra-processed food are associated with an increased risk of 32 damaging health outcomes , including higher risk for cancer, major heart and lung conditions, gastrointestinal issues, obesity, type 2 diabetes, sleep issues, mental health disorders and early death.

Sara Moniuszko is a health and lifestyle reporter at CBSNews.com. Previously, she wrote for USA Today, where she was selected to help launch the newspaper's wellness vertical. She now covers breaking and trending news for CBS News' HealthWatch.

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ORIGINAL RESEARCH article

Explainable artificial intelligence and microbiome data for food geographical origin: the mozzarella di bufala campana pdo case of study.

• 1 Department of Soil, Plant, and Food Sciences, Faculty of Agricultural Science, University of Bari Aldo Moro, Bari, Italy
• 2 Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Bari, Italy
• 3 Department of Agriculture, School of Agriculture and Veterinary Medicine, University of Naples Federico II, Portici, Italy
• 4 Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, Bari, Italy

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Identifying the origin of a food product holds paramount importance in ensuring food safety, quality, and authenticity. Knowing where a food item comes from provides crucial information about its production methods, handling practices, and potential exposure to contaminants. Machine learning techniques play a pivotal role in this process by enabling the analysis of complex data sets to uncover patterns and associations that can reveal the geographical source of a food item.This study aims to investigate the potential use of explainable artificial intelligence for identifying the food origin. The case of study of Mozzarella di Bufala Campana PDO has been considered by examining the composition of the microbiota in each samples. Three different supervised machine learning algorithms have been compared and the best classifier model is represented by Random Forest with an Area Under the Curve (AUC) value of 0.93 and the top accuracy of 0.87. Machine learning models effectively classify origin, offering innovative ways to authenticate regional products and support local economies. Further research can explore microbiota analysis and extend applicability to diverse food products and contexts for enhanced accuracy and broader impact.

Keywords: Explainable artificial intelligence, machine learning, microbiome, Food origin, PDO

Received: 28 Feb 2024; Accepted: 13 May 2024.

Copyright: © 2024 Magarelli, Novielli, De Filippis, Magliulo, Di Bitonto, Diacono, Bellotti and Tangaro. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Sabina Tangaro, Department of Soil, Plant, and Food Sciences, Faculty of Agricultural Science, University of Bari Aldo Moro, Bari, 70121, Italy

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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• Published: 11 May 2024

Natural approach of using nisin and its nanoform as food bio-preservatives against methicillin resistant Staphylococcus aureus and E.coli O157:H7 in yoghurt

• Walaa M. Elsherif 1 , 2 ,
• Alshimaa A. Hassanien 3 ,
• Gamal M. Zayed 2 , 4 &
• Sahar M. Kamal 5  

BMC Veterinary Research volume  20 , Article number:  192 ( 2024 ) Cite this article

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Metrics details

Natural antimicrobial agents such as nisin were used to control the growth of foodborne pathogens in dairy products. The current study aimed to examine the inhibitory effect of pure nisin and nisin nanoparticles (nisin NPs) against methicillin resistant Staphylococcus aureus (MRSA) and E.coli O157:H7 during the manufacturing and storage of yoghurt. Nisin NPs were prepared using new, natural, and safe nano-precipitation method by acetic acid. The prepared NPs were characterized using zeta-sizer and transmission electron microscopy (TEM). In addition, the cytotoxicity of nisin NPs on vero cells was assessed using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The minimum inhibitory concentrations (MICs) of nisin and its nanoparticles were determined using agar well-diffusion method. Further, fresh buffalo’s milk was inoculated with MRSA or E.coli O157:H7 (1 × 10 6 CFU/ml) with the addition of either nisin or nisin NPs, and then the inoculated milk was used for yoghurt making. The organoleptic properties, pH and bacterial load of the obtained yoghurt were evaluated during storage in comparison to control group.

The obtained results showed a strong antibacterial activity of nisin NPs (0.125 mg/mL) against MRSA and E.coli O157:H7 in comparison with control and pure nisin groups. Notably, complete eradication of MRSA and E.coli O157:H7 was observed in yoghurt formulated with nisin NPs after 24 h and 5th day of storage, respectively. The shelf life of yoghurt inoculated with nisin nanoparticles was extended than those manufactured without addition of such nanoparticles.

Conclusions

Overall, the present study indicated that the addition of nisin NPs during processing of yoghurt could be a useful tool for food preservation against MRSA and E.coli O157:H7 in dairy industry.

Peer Review reports

Introduction

Using of bacteriocins such as nisin alone or combined with other natural materials such as essential oils, could be represented as a useful candidate for improving the microbiological quality and maintaining the sensory properties of milk and milk products [ 1 , 2 ]. The utility of nisin as a bio preservative in food industry has been approved and this bacteriocins was effective enough to extended shelf life in regions with inadequate preservation facilities such as developing countries [ 3 ]. Nisin is a natural water-soluble antibacterial peptide (AMP) composed of 34 amino acid residues produced by Lactococcus lactis. It has the ability to inhibit the growth of some foodborne pathogens and many of Gram-positive spoilage bacteria [ 4 , 5 ]. This antibacterial peptide is generally regarded as a safe food preservative by the joint Food and Agriculture Organization and World Health Organization (FAO/WHO), also by the US Food and Drug Administration (FDA) [ 6 , 7 ]. Based on aforementioned permissions, it is widely commercialized as a safe and natural food preservative in the food industry in more than 50 countries around the world [ 8 ].

The antibacterial activity of nisin in food is depending on several factors such as its solubility, pH and structural properties of target bacteria. It could exhibit potent antimicrobial activities against many species of Gram-positive pathogens, while it has little effect against Gram-negative bacteria, yeast and fungi due to their outer membrane barriers [ 9 ]. The exact antibacterial mechanism of nisin is attributed to the passage of nisin through the cell wall of bacteria and its interaction with lipid II, which considered as an essential element in the bacterial cell wall [ 9 ].

There are some obstacles that can hinder the antimicrobial efficacy of free nisin as a food bio preservative such as its ability to interact with food components (e.g. proteolytic enzymes, phospholipids, fatty acids and proteins), high pH and many other food additives. These factors could drastically reduce or completely diminish the antimicrobial effect of nisin [ 10 ]. Hence, different strategies were developed to improve the preservative efficacy of nisin such as liposomes [ 11 ] and nanoparticles [ 12 ]. However, these reported techniques are not suitable for applications in food industries due to the utility of inorganic solvents and chemical compounds, in addition to they are expensive and complicated. For these reasons, alternative organic chemicals and solvents or green synthesized nanoparticles were developed to overcome the inactivation of free nisin by many food components through protecting nisin and releasing it in sustained manner [ 13 ]. For instance, acetic acid, a well-known biocompatible organic acid, has no adverse effects, no dietary restrictions and it is generally recognized as a safe food additive. This organic acid is commonly used, as a natural preservative, in the preservation of food especially in cheese and dairy products where it inhibit the development of bacteria, yeast and fungi [ 14 , 15 ]. Besides acetic acid, tween 80 has a great potential to stabilize nanoparticles dispersion through formation of a protective coat around the nanoparticles, so it was used in food without adverse health effect [ 16 , 17 ].

Application of nisin in dairy industry was reported in more than 55 countries due to its prominent antimicrobial, technological characteristics, safety, stability and flavorless. Commercially, nisin was used in several food matrices to ensure safety, extend shelf life, and to improve the microbial quality either through addition of nisin directly in its purified form or through its production in situ by live bacteria [ 18 , 19 , 20 ]. For instance, nisin was added as a bio-preserving ingredient in some kinds of cheese [ 21 , 22 , 23 ], skim milk and whole milk [ 24 , 25 , 26 , 27 ]. Nisin has a potent antibacterial effect against spore-forming bacteria that are the main spoilage concerns in the food industry [ 26 ]. However, several factors such as neutral pH [ 4 ], Fat% [ 25 ], protein% [ 28 ] as well as calcium and magnesium concentrations that can reduce the antimicrobial efficacy of nisin were reported when used directly in dairy foods [ 15 , 29 , 30 ]. Certain previously reported strategies, such as encapsulation and nano-encapsulation of nisin, were applied to increase the antimicrobial efficacy of nisin in dairy industry [ 31 , 32 ]. . Importantly, there is no available data about the use of nisin or nisin NPs as antimicrobial agents during yoghurt preparation.

Accordingly, the current study was designed to prepare nisin NPs by simple nanoprecipitation technique using natural, biocompatible and safe materials. Also the aims of this study were extended to investigate the antibacterial effect of obtained nanoparticles on MRSA and E.coli O157:H7 during manufacturing and storage of yoghurt. Additionally, the effect of the used nisin NPs on the organoleptic properties of yoghurt was addressed.

Materials and methods

Acetic acid (Merck Co., Germany), nisin (Sigma Aldrich from Lactococcus lactis , potency ≥ 900 IU/mg, purity ≥ 95%, CAS Number 1414-45-5), Brain Heart Infusion (BHI) (BBL 11,407, USA), phosphate buffer saline (PBS) (Oxoid, Basingstoke, UK) were purchased and used as received. Polyethylene glycol sorbitan monooleate (Tween 80) was purchased from Sigma Aldrich. Additionally, Mueller Hinton agar (M173) was purchased from HiMedia (Pvt., India), and LAB204 Neogen Company. While, 0.5 McFarland Standard (8.2 log 10 CFU/ml) (Cat. No. TM50) was purchased from Dalynn Biologicals Co. The deionized water was obtained from the Molecular Biology Unit, Assiut University, Egypt.

Preparation of nisin nanoparticles

Nisin (2 mg/mL) was completely dissolved in 100 mL of 0.1 M aqueous acetic acid solution with the aid of sonication using cold probe sonication (UP100H Hielscher Ultrasound). Then, 50 mL of deionized distilled water was gradually added to the nisin solution while maintaining the pH value within the range of 2.5 to 3. Further, 0.01% tween 80 was added as a stabilizer and the mixture was constantly stirred at 25 oC for 7 h to eliminate acetic acid as much as possible. Finally, the nanoparticles suspensions were then sonicated for 5 min before stored at refrigerator temperature for further use. The obtained nanoparticles were examined for size, shape, antibacterial activity and stability after six months.

Characterization of the prepared nisin NPs

Dynamic light scattering (dls).

The prepared nanoparticles was characterized by DLS at a fixed scattered angle of 90° using a Zetasizer, ZS 90 (3000 HS, Malvern Instruments, Malvern, UK) at the Nanotechnology Unit, Al-Azhar University at Assiut, Egypt. Measurements were taken at 25 °C and Zetasizer® software (version 7.03) was used to collect and analyze the data [ 33 ].

Fourier-transform infrared spectroscopy (FTIR)

FTIR was performed at the Chemistry Department at the Faculty of Science, Assiut University. This experiment was used to identify the functional groups and the fingerprint of the molecule. Samples were prepared by compressing potassium bromide with either free nisin or NNPs into small discs. The produced discs were then scanned using FTIR spectrometer (FTIR, NICOLET, iS10, Thermo Scientific) in the wave number ranged from of 4000 to 500 cm − 1 [ 34 ].

High resolution transmission electron microscopy (HRTEM)

The morphology of the prepared nisin NPs was determined using HRTEM (JEM2100, Jeol, Japan) at the Electronic Microscope Unit, National Research Center, Egypt. The sample was diluted with deionized water, and a small drop of nisin NPs was dropped onto 200-mesh copper coated grids at room temperature and negatively stained with uranyl acetate for 3 min. Excess liquid was removed using Whatman filter paper and samples were dried at room temperature [ 35 ].

Bacterial strains and inoculum preparation

The tested pathogens (MRSA and E. coli O157:H7) were previously isolated from dairy products (milk, cheese and yoghurt) samples by culture method and identified using conventional biochemical method and PCR at a certified food lab, Animal Health Research Institute (AHRI), Egypt [ 36 , 37 ]. These isolates were inoculated in trypticase soy broth (Himedia, India) and incubated at 37˚C for 24 h, then co-cultured on selective agars such as MRSA agar base (Acumedia, 7420, USA) and Sorbitol MaCconkey agar (Himedia, India) [ 38 , 39 ] for MRSA and E. coli O157:H7, respectively. The isolates were inoculated in BHI broth and incubated at 37 °C for 24 h until turbidity was comparable to a 0.5 McFarland turbidity standard. Before inoculating bacteria in milk, the inoculum was washed twice in PBS and then re-suspended in skim milk.

Determination of minimum inhibitory concentration (MIC) of free nisin and nisin nanoparticles against MRSA and E. Coli O157:H7

To determine the MIC of nisin NPs against MRSA and E.coli O157:H7, the agar well diffusion method was used according to Suresh et al. [ 40 ] with minor modifications. In brief, 0.1 mL of the previously prepared bacterial suspensions was spread on Mueller Hinton agar plates and left for 10 min to be absorbed. Then, 8 mm wells were punched into the agar plates for testing the antimicrobial activity of nanoparticles. One-hundred µl of different concentrations of free nisin and nisin NPs (from 0.0313 mg/mL to 2 mg/mL) were poured onto the wells. One well in each plate contained 100 µL of sterile deionized water was kept as a negative control. After overnight incubation at 35 ± 2 °C, the diameters of the inhibition zones were observed and measured in mm [ 41 ]. Each concentration was performed in triplicate.

Assessment of nisin nanoparticles cytotoxicity

The biocompatibility and the cytotoxicity of the nisin NPs were evaluated using a MTT assay against a Vero cell line after culture at 37 °C in a humidified incubator with 5% CO 2 in Dulbecco’s Modified Eagle’s Medium supplemented with 10% Fetal Bovine Serum. The cells were seeded into a 96-well plate at a density of 1 × 10 4 cells/well overnight before treatment. Different dilutions (0.5×MIC, MIC, 2×MIC, 4×MIC) of optimized nisin NPs were added to the seeded cells. Cells without nanoparticles served as control group. After 72 h, the consumed media was replaced with phosphate buffered saline, 10 µL from 12 mM MTT stock solution was added to each well and cells were incubated for 4 h at 37 °C. Next, 50 µL DMSO was added to dissolve formazan crystals and then the absorbance was measured at 570 nm using a BMG LABTECH®-FLUO star Omega microplate reader (Ortenberg, Germany). All experiments were performed in triplicate.

Antibacterial efficacy of the free nisin and nisin NPs against MRSA and E. Coli O157:H7 during manufacturing and storage of yoghurt

Fresh milk was heated at 85 °C for 5 min in water bath then suddenly cooled. The prepared inoculums were added to the warmed milk (41 ºC) in a count of 10 6 CFU/mL. The inoculated milk was divided into four parts for further use as following, part 1 is the positive control (contained MRSA or E. coli O157:H7 only, one jar each), part 2 (contained MRSA or E. coli O157:H7 with nisin NPs at MIC and 2×MIC, two jars each), part 3 (contained MRSA or E. coli O157:H7 with free nisin at MIC and 2×MIC, two jars each) and part 4 (negative control; free from pathogens and contained free nisin or nisin NPs only, one jar each). After inoculation of the different treatments, yoghurt was manufactured according to Sarkar [ 42 ] by adding 2% yoghurt starter culture ( Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus ) at 41 °C to milk. The prepared yoghurt was placed in a constant-temperature incubator at 40 °C until pH reached 4.6 to 4.5. Finally, the obtained products were stored at refrigeration temperature (4 ± 1 °C) for 5 days. Samples were collected just after manufacturing of yoghurt and every 2 days during storage, then tested for the count of MRSA using MRSA agar base media [ 43 ], and E. coli O157:H7 using Sorbitol MacConkey (SMAC) agar plates [ 44 ]. In addition, pH values were determined in the examined samples as previously described by Igbabul et al. [ 45 ]. In brief, 10 g o f yoghurt sample was dissolved in 100 mL of distilled water. The mixture was left to equilibrate at room temperature. Then, the pH of the samples was then measured by a pH meter (Microprocessor pH meter, pH 537, WTW, Germany).

Organoleptic assay of manufactured yogurt

Pathogen-free yoghurt jars (negative control) were prepared with two concentrations of either free nisin or nisin NPs (MIC and 2×MIC) as previously mentioned to be used for organoleptic evaluation. Thirty-five panelists were selected in teams of different ages, sex and education. The perception of consumers toward samples with two concentrations of nisin NPs was recorded. Consumers were asked to evaluate the color, flavor, mouth feel, appearance, and overall acceptability (OAA) of the prepared yoghurt samples containing nisin NPs [ 46 ]. The scale points were excellent (5); very good (4); good (3); acceptable (2); and poor (1).

Statistical analysis

One-way analysis of variance (ANOVA) was performed using the SPSS program (SPSS Inc., Chicago, IL, USA, 18) to determine the statistical significance of differences between groups. Results with P  < 0.05 were considered statistically significant. The microbiological and cytotoxicity assay data were prepared using Excel software version 2017. While, the FTIR results were performed using Origin Lab 2021 for graphing and analysis. All experiments were carried out in triplicate.

Characterization of the prepared nanoparticles

The freshly prepared nisin NPs had 26.55 nm size and PDI 0.227 as determined by zetasizer. While, the diameter of the same after 6 months at refrigeration temperature was 86.50 nm with a PDI equal to 0.431 (Table  1 ). These results indicated that reasonable small-sized particles of nisin were obtained by precipitation technique using acetic acid. The small size of the prepared particles and the small PDI range (from 0.2 to 0.4) indicated a mono size dispersion and a good stability of the prepared nisin NPs.

The size and morphology of the freshly prepared nisin NPs and after 6 months of storage were measured by HRTEM are presented in Fig.  1 . Both freshly prepared and stored nisin NPs were approximately uniform in size with adequate distribution of particles. The shape of the particles was nearly spherical with slightly a bit of agglomeration just after 6 months of storage. The average size of freshly prepared nisin NPs was 7.35 nm while, after 6 months was 15.4 nm. The size of particles determined by TEM is usually smaller than the dynamic particles determined by zeta-sizer because TEM determine the actual particle diameter while zeta-sizer determine the particles diameter with adjacent moving layers of solvents.

The TEM images of freshly prepared nisin NPs (A) and after 6th months of storage (B)

Figure  2 showed the FTIR of pure and nisin NPs; both spectrum showed the characteristic peaks of nisin at 3425, 1599 and 1493 cm − 1 corresponded to O-H stretching of COOH, C = O stretching of amide I and N-H bending amide II. Bands 1530 cm − 1 in free nisin indicated the stretching of amid II and which, increased to 1549 cm − 1 in nisin NPs that indicated increase the H- bond in nano form than free one. The results of FTIR spectrum confirmed that the formation of nisin NPs did not result in any chemical changes or interaction of nisin with used the materials. These results also demonstrated the suitability of the applied method for the preparation of chemically stable and small-sized nisin NPs.

The FTIR of pure nisin and nisin NPs

Assessment of Nisin nanoparticles cytotoxicity

In the present study, Veros cells were exposed to nisin NPs for 48 and 72 h, and the cytotoxicity was measured by MTT assays. Results showed that the MIC did not exhibit an anti-proliferation effect (Fig.  3 ). Interestingly, even at very high concentrations (4xMIC), there were no cytotoxicity effect as the percentage of viable cells reach 92% and 89.98% after 48 and 72 h, respectively. The obtained findings confirmed the safety and good biocompatibility of the prepared nisin NPs at MIC level.

Cytotoxicity and cell viability of different concentrations nisin NPs using Vero cells after 48 and 72 h using MTT assay

MIC of free nisin and nisin NPs against MRSA and E. Coli O157:H7

The efficacy of the free nisin and prepared nisin NPs against MRSA and E. coli O157:H7 was investigated using agar well diffusion assay (Table  2 ). Nisin and its nanoparticles showed potent antibacterial effect against MRSA than E. coli O157:H7. The MICs of nisin and nisin NPs toward MRSA were 0.0625 and 0.0313 mg/mL, respectively. While, 0.125 mg/mL was the MIC of both nisin and nisin NPs against E. coli O157:H7. Of note, growth inhibition zone was not observed against MRSA at 0.0313 mg/mL of nisin, and toward E. coli O157:H7 at both 0.0625 and 0.0313 mg/mL nisin (Table  2 ). On the other hand, the prepared nisin NPs could produce inhibition zones against MRSA with a mean diameter ranged from 25.4 ± 2.1 mm to 7.1 ± 0.89 mm at concentrations of 2 to 0.0313 mg/mL, respectively. Also, the nisin NPs showed anti- E. coli O157:H7 activity at different concentrations of 2, 1, 0.5, 0.25 and 0.125 mg/mL with average size of 20.1, 15.4, 12.7, 9.5 and 7.2 mm of the inhibitory zones, respectively. There were no inhibition zones against E. coli O157:H7 at 0.0625 and 0.0313 mg/mL of nisin NPs. Overall, the obtained findings indicated that the most effective MICs of nisin and nisin NPs for both organisms were 0.125 mg/mL (Table  2 ).

Antibacterial effect of nisin and nisin NPs against MRSA and E. Coli O157:H7 during manufacturing and storage of yoghurt

Figure  4 presented the antibacterial activity of nisin against the examined foodborne pathogens (MRSA and E. coli O157:H7). Here, nisin at 0.125 and 0.25 mg/ml could induce antibacterial effect against MRSA (3.3 and 3 log 10 CFU/g, respectively) after 24 h of yoghurt storage. However the effect was not higher as in case of nisin NPs (2.3 and 1 log 10 CFU/g) at the same concentrations and time of storage. While, the inhibitory impact of the free nisin on E. coli O157:H7 was observed after 24 h (3.7 log 10 CFU/g) and 3 days (3.8 log 10 CFU/g) of storage at the concentrations of 0.25 and 0.125 mg/mL, respectively. The pathogens were still detected till the end of the experiment in nisin treated yoghurt (Fig.  4 ).

Antibacterial effect of free nisin (A) and nisin NPs (B) on MRSA and E.coli O157:H7 during manufacturing and storage of yoghurt

On the other hand, there was a clear reduction in mean count of MRSA and E.coli O157:H7 in the laboratory-manufactured yoghurt supplemented with different concentrations (0.125 and 0.25 mg/mL) of nisin NPs. A complete inhibition of MRSA was observed after 24 h and at the 3rd day of storage by 0.25 and 0.125 mg/mL of nisin NPs, respectively (Fig.  5 ). While, E. coli O157:H7 was undetectable at the 5th day of storage with 0.25 mg/mL nisin NPs, however it was still detected till the end of the experiment in either yoghurt inoculated with 0.125 mg/mL nisin NPs or in the positive control group (Fig.  4 ). Taken together, the antimicrobial count tests revealed that the free nisin is not effective as the nisin NPs at same time points during processing and storage of yoghurt.

During storage, the pH did not change significantly between different treatments. However, the negative control group showed little decrease in pH in comparison to other groups at the 3rd and 5th day of storage (3.5 and 3, respectively).

Evaluation of pH levels during processing and storage of yoghurt inoculated with different concentrations of free nisin or nisin NPs

Organoleptic evaluation of the laboratory-manufactured yoghurt

Figure  6 clarified that there was no difference in the sensory properties between the different groups (contained 0.125 or 0.25 mg/mL nisin (Fig. 6A) or nisin NPs (Fig. 6B)) in comparison to the control group. The OAA of yoghurt inoculated with 0.125 mg/mL and 0.25 mg/mL of free nisin was 3 and 2.5, respectively (Fig. 6A). While, the control samples had the highest score in mouth feel (4.5), followed in order with yoghurt loaded with 0.125 mg/mL and 0.25 mg/mL nisin NPs (3.8 and 2.7, respectively). Additionally, the overall acceptability (OOA) of control, 0.125 mg/mL and 0.25 mg/mL nisin NPs groups was 4, 3.7 and 3, respectively (Fig. 6B). Such findings indicated the high acceptability of yoghurt containing different concentrations of nisin NPs than those inoculated with free nisin.

Organoleptic properties of yoghurt inoculated with different concentrations of free nisin and nisin NPs

The current study elucidated for the first time the inhibitory effect of free nisin and nisin NPs on two of the most common foodborne pathogens (MRSA and E. coli O157:H7) during processing and storage of laboratory manufactured yoghurt. Strikingly, adding of nisin NPs to yoghurt could induce much higher antibacterial effect on MRSA and E. coli O157:H7 with high consumer acceptability than free nisin. Accordingly, nisin NPs could be a useful and effective bio-preservative candidate against MRSA and E. coli O157:H7 in dairy industry.

The present study revealed that nisin NPs was prepared by a novel and safe method using natural material such as acetic acid which is commonly applied in food products. Chang et al. [ 47 ]. prepared ultra-small sizes of nisin NPs by nanoprecipitation method using HCL while we obtained much smaller particle size of NNPs using acetic acid which is more safer, less toxic and accepted by consumers. The particle size determined by TEM is smaller than the size measured by DLS this difference could be attributed to the removal of solvent and shrinking of nanoparticles during the drying of nisin NPs samples for TEM investigations. In addition, DLS measures the hydrodynamic diameter of the dispersed moving particles with the surrounding moving layers of solvents [ 48 , 49 ].

The result of FTIR was in consistent with that of Flynn et al. [ 50 ]. Herein, we found that the -OH stretching peak of nisin NPs displayed a greater intensity than that of free nisin, which indicated a stronger hydrogen bonding formation within nisin NPs. In case of free nisin, the peak at 1620 cm − 1 corresponding to COO − was shifted to 1610 cm − 1 in nisin NPs indicating that the hydrogen bonding was increased within nisin NPs. In contrast, the amid II band in free nisin appeared at 1530 cm − 1 became more obvious at 1549 cm − 1 in nisin NPs which was in agreement with Webber et al. [ 51 ]. . Band of amide I at wave number of 1632 cm − 1 could be due to the change in the structure of free nisin when converted into nisin NPs by using natural acetic acid.

In food chain, nisin has been approved for use in over 50 countries due to its safety and its potent antimicrobial activity without inducing microbial resistance [ 52 ]. Of particular note, the FAO/WHO Codex Committee and US FDA allow using nisin as a food additive in dairy products at a concentration up to 250 mg/kg [ 1 , 53 ]. Moreover, European Food Safety Authority [ 54 ] reported that nisin has been shown to be non-toxic to humans and it is safe as a food preservative for dairy and meat products. In the current study, the examined organisms (MRSA and E. coli O157:H7) have been involved in many food outbreaks worldwide as well as their resistance to many antibiotics, considered a challenge to be controlled [ 55 , 56 , 57 ]. Therefore, the present study could be a useful alternative strategy to avoid the possible health hazards of these organisms after consumption of yoghurt using either nisin or nisin NPs as natural food preservatives.

The obtained results revealed that the MICs of nisin and nisin NPs against MRSA were lower than that of E. coli O157:H7. This could be due to the ability of nisin to penetrate the cell wall of Gram-positive bacteria, however, it is difficult for nisin to penetrate the outer membrane barrier of Gram-negative bacteria [ 58 ]. Nisin could destroy bacteria through two mechanisms, either by making pores in the plasma membrane or by inhibiting the cell wall biosynthesis through binding to lipid II [ 59 , 60 , 61 ]. Importantly, the obtained results in the current study showed that that MIC of nisin NPs against MRSA was lower than that of pure nisin. Similarly, Zohri et al. [ 62 ] reported that the MICs of nisin and Nisin-Loaded nanoparticles was 2 and 0.5 mg/mL after 72 h of incubation period with the S. aureus samples, respectively. In addition, Moshtaghi et al. [ 63 ] examined the antibacterial effect of nisin on S. aureus and E. coli at different pH values and they found that the MICs against S. aureus were ranged from 19 to 312 µg/mL of nisin at pH levels from 8 to 5.5, respectively. While for E. coli , the MICs were from 78 to 1250 µg/mL at the same range of pH, respectively [ 63 ].

Interestingly, nisin inhibited the pathogenic foodborne bacteria and many other Gram-positive food spoilage microorganisms [ 13 ]. In the present study, evaluation of the kinetic growth of MRSA and E. coli O157:H7 based on the total counts in the laboratory manufactured yoghurt revealed that nisin NPs was able to inhibit more effectively the growth of such foodborne pathogens than free nisin during manufacturing and storage of yoghurt. These findings were in concurrent with those obtained by Zohri et al. [ 62 ] who demonstrated that nisin-loaded chitosan/alginate nanoparticles showed more antibacterial effect than free nisin on the growth of S. aureus in raw and pasteurized milk samples. Additionally, nisin Z in liposomes can provide a powerful tool to improve nisin stability and inhibitory action against Listeria innocua in the cheddar cheese [ 64 ]. In our study, nisin NPs showed a complete inhibition of MRSA after curdling of yoghurt and reduced the survivability of E. coli O157:H7 when applied at two different concentrations during storage of such product. Nisin NPs with high specific surface area could be easily attached to the target cell surface leading to increased permeability of the cell membrane, and finally cause bacterial cell death. Furthermore, nisin NPs were thermo-tolerant because of the internal non-covalent interactions in the nanoparticles [ 4 , 65 ]. Additionally, the decline in the mean count of the examined pathogens (MRSA and E.coli O157: H7) in the current study may be due to the effect of low pH (high acidity) of yoghurt that leads to shrinkage and death of the bacterial cells [ 66 ]. Similarly, Al-Nabulsi et al. [ 67 ] reported that the combination of a starter culture, low temperature, and pH ( ∼ 5.2) had inhibitory effects on the growth of S. aureus .

The effect of adding different levels of nisin and nisin NPs on OAA scores of yoghurt was recorded and the obtained results were in agreement with Hussain et al. [ 68 ], Radha [ 3 ], and Gharsallaoui et al. [ 4 ] who reported that a Nigerian fermented milk product had acceptable sensory scores till 25th day of storage when loaded with nisin at 400 IU/mL. Additionally, Chang et al. [ 47 ] said that the thermal treatments are known to cause undesirable changes in the sensory, nutritional and/or technological properties of milk. Taking advantage of the antimicrobial action of nisin NPs against several spoilage and pathogenic microorganisms, this innovative non-thermal food preservative offers the inactivation of microorganisms with minimal impact on the quality, safety, nutritional values and acceptability of dairy products.

Overall, as the demand for preservative-free food products increased, natural antimicrobials have gained more and more attention because of their effectiveness and safety. Consequently, the current study investigated that the addition of nisin NPs to milk for manufacturing of yoghurt can be used as an innovative preventive measure to inhibit the contamination with foodborne pathogens. However, further researches are required to determine the effective and safe dose of nisin NPs for application in other dairy products.

The present study prepared nisin NPs using acetic acid by precipitation method and the obtained particles were small in size with good stability and consumer acceptability. The antibacterial effect of nisin and nisin NPs against MRSA and E. coli O157:H7 in yoghurt was impressive. Additionally, the studied nanoparticles did not affect the sensory and textural characteristics of the finished product. Hence, this study could be useful for yoghurt makers and dairy products factories through using this novel preservation technology to inhibit the growth of MRSA and E. coli O157:H7, in yoghurt and dairy products, and subsequently avoid food spoilage and foodborne diseases.

Data availability

All data and materials are available here in the current study.

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W.M.E., A.A.H., G.M.Z., and S.M.K. conceived and designed the experiment. W.M.E., A.A.H., G.M.Z., and S.M.K. collected the experimental data. W.M.E., A.A.H., and S.M.K. performed the microbiological analysis. A.A.H. and G.M.Z. performed the preparation and analysis of nanoparticles. W.M.E. and S.M.K. performed the statistical analysis. All authors interpreted the data. W.M.E. wrote the first draft of the manuscript. All authors reviewed the manuscript.

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Elsherif, W.M., Hassanien, A.A., Zayed, G.M. et al. Natural approach of using nisin and its nanoform as food bio-preservatives against methicillin resistant Staphylococcus aureus and E.coli O157:H7 in yoghurt. BMC Vet Res 20 , 192 (2024). https://doi.org/10.1186/s12917-024-03985-1

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Department of Agricultural, Food, and Resource Economics Innovation Lab for Food Security Policy, Research, Capacity and Influence

Effect of Pesticide Use on Crop Production and Food Security in Uganda

May 14, 2024 - Linda Nakato, Umar Kabanda, Pauline Nakitende, Tess Lallemant & Milu Muyanga

The increasing pest proliferation has continued to cause a serious threat to food security in Uganda. This study explores the impact of pesticide adoption on food security in Uganda. Specifically, it seeks to assess whether the use of pesticides ensures food security, with crop productivity serving as an intervening variable. Employing the control function approach with fixed effects estimation on a dataset comprising 1,656 households spanning the periods 2013/2014, 2016/2015, and 2018/19 to 2019/20 obtained from the Uganda National Panel Survey, the study reveals several determinants influencing pesticide use in Uganda. The findings also highlight that the adoption of pesticides demonstrates a positive influence on crop productivity. However, when assessed through indicators such as Food Consumption Score (FCS), Minimum Acceptable Household Food Consumption (MAHFP), and Household Dietary Diversity Score (HDDS) at the pre-harvest stage, the results do not indicate a statistically significant correlation of pesticide use and food security outcomes. Consequently, beyond enhanced crop productivity and the pre-harvest activities focused on in the study, it is imperative to consider the post-harvest application of pesticides to comprehensively explain how pesticide use effects food security in Uganda. Based on the positive link between pesticides and crop productivity, its recommended that government should increase awareness on and access of insecticides among farmers. Given that insects are the main pests damaging crops in Uganda. It is also important for Uganda to reform and reactive a regulatory framework having a licensing system to regulate private local market dealers’ sale of pesticides. Given that the majority of the households purchase their pesticides from private traders in the local/village market. This approach might improve the quality of pesticide purchased by farmers and, increase pesticide use to diversify produce of more nutritious foods, to ultimately enhance access and nutrient intake per meal in Uganda.

 Pesticide use, crop productivity, food security.

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Americans’ Perceptions about Fast Food and How They Associate with Its Consumption and Obesity Risk

Jungwon min.

1 Systems-Oriented Global Childhood Obesity Intervention Program, Fisher Institute of Health and Well-being, College of Health, Ball State University, Muncie, IN

2 Grand Forks Human Nutrition Research Center, US Department of Agriculture-Agricultural Research Service, Grand Forks, ND

3 Department of Health Behavior and Policy, School of Medicine, Virginia Commonwealth University, Richmond, VA

Jayanthi Kandiah

4 Department of Nutrition and Health Sciences, College of Health, Ball State University, Muncie, IN

Associated Data

We aimed to systematically examine Americans’ perceptions of fast food (FF) and how these perceptions might affect fast food consumption (FFC) and obesity risk. We searched PubMed and Google for studies published in English until February 17, 2017 that reported on Americans’ perceptions (defined as their beliefs, attitudes, and knowledge) regarding FF as well as those on their associations with FFC and obesity risk. Thirteen articles met inclusion criteria. Limited research has been conducted on these topics, and most studies were based on convenience samples. A 2013 nationally representative phone survey of about 2000 subjects showed that one-fifth of Americans thought FF was good for health, whereas two-thirds considered FF not good. Even over two-thirds of weekly FF consumers (47% of the total population) thought FF not good. Americans seem to have limited knowledge of calories in FF. Negative and positive FF perceptions were associated with FFC. Those who consumed less FF seemed more likely to view FF negatively. When Americans valued the convenience and taste of FF and preferred FF restaurants with kid's menus and play areas, they were likely to purchase more FF. Available research indicates neither perceived availability of FF nor Geographical Information System (GIS)-based FF presence in the neighborhood has significant associations with weekly FFC. No studies examined potential links between FF perceptions and obesity risk. Americans’ perceptions of FF and how they might associate with FFC and obesity risk are understudied. Considerable variation was observed in Americans’ perceptions and FFC.

Introduction

Consumption of fast food (FF, food being mass-produced and served quickly) is common in the United States and many other industrialized countries, and it has been increasing steadily in some developing countries as well owing to factors such as its convenience, low cost, consistent taste, easy access through a variety of restaurant chains, and the FF industry's marketing effort ( 1 , 2 ). A 2013 survey showed that about half of Americans reported eating at FF restaurants at least weekly ( 3 ), and ∼80% of adults went to FF restaurants at least once per month ( 3 , 4 ). FF is one of the major components of Americans’ diet, as about 11% of their calories are derived from fast food consumption (FFC) among adults ( 5 ).

FF is often made with ingredients such as high-fat meat, refined grains, and added sugar and fats ( 6 ) and is high in sodium, saturated fat, and cholesterol, which are harmful to health ( 7 , 8 ). FF often contributes to higher energy intake compared with traditional food items ( 9 ). Multiple studies have found that frequent FFC is associated with elevated BMI and cholesterol, and increased risk for obesity, hypertension, and diabetes ( 2 , 10–12 ). As obesity is becoming a global public health crisis and has resulted in high health and economic costs ( 13 ), researchers have recommended avoiding frequent FFC ( 14 , 15 ).

Although some FF industries have altered their menus to include healthier options (e.g., whole-wheat buns, low-fat milk, grilled chicken nuggets), their aggressive FF marketing via television, mobile devices, and social media promotes liking of FF, but not specifically healthier FF choices ( 16 ). Research suggests that heavy television viewing might lead to less negative and more positive beliefs about FF's health consequences ( 17 ). Compared with adults, children are more susceptible to frequent FFC owing to peer influence and impulsive actions ( 18 ). Also, subgroups of American adults who have the highest percentage of total energy intake from FF include young adults (16%), non-Hispanic blacks (15%), and obese individuals (13%) ( 5 ). Young non-Hispanic blacks have the greatest intake from FF, contributing 21% of their total energy intake.

An inverse socioeconomic gradient in FFC among adults and children has also been reported in the United States ( 19 , 20 ). Low-income and food-insecure people consume more FF owing in part to lack of access to healthy and affordable foods ( 21 ) and perceived barriers of higher prices for healthy foods and lower prices for FF ( 22 ), which also contributes to sustaining FF as a major contributor to Americans’ diets. Additionally, a systematic review found that FF restaurants are more prevalent in low-income areas compared with middle- to higher-income areas and in areas with higher concentrations of ethnic minority groups compared with Caucasians ( 23 ). Disproportionately high access to FF in the United States is prevalent in predominantly black neighborhoods ( 24 ).

Some research suggests that individuals’ beliefs, attitudes, and knowledge, such as perceived barriers, self-confidence, or risks/benefits in dietary behaviors, statistically predict eating behavior ( 25 ); those having strong confidence in diet control are less likely to consume high-calorie diets ( 26 ). Impulsive individuals prefer convenience meals more than health-conscious individuals ( 27 ), whereas those who pay more attention to food labels are more likely to consume a healthy diet. Yet, no study has systemically examined how Americans think about FFC, and whether they want to limit or continue their FFC, as reducing FFC has been recommended for preventing obesity. Differences in nutrition- and health-related attitudes, beliefs, and knowledge, including making informed food choices and awareness of nutrition-related health risks ( 28 ), could be implicated in high FFC in the United States.

This study aimed to systematically examine Americans’ perceptions of FF, defined as their beliefs, attitudes, and knowledge regarding FF, and to assess how FF perceptions are related to FFC and obesity risk.

Literature search

We searched PubMed and Google ( http://google.com/ ) for relevant studies published in English through February 17, 2017. We used the following related keywords with Medical Subject Heading (MeSH) terms and conducted title and abstract searches: fast food, intake, consumption, knowledge, attitude, belief, perception, obesity, overweight, weight, BMI, the United States, and America. We also consulted several experts in the field. The search yielded 169 titles. We reviewed the titles and abstracts to exclude duplicates and publications not related to the topic, which resulted in 69 publications. We then reviewed the full papers. Thirteen publications met our inclusion criteria, with 3 of them brought to our attention by experts we consulted ( Figure 1 ).

Flowchart of literature search and study selection procedure. FF, fast food; FFC, fast food consumption.

Study inclusion and exclusion criteria

Inclusion criteria were: 1) an original study (i.e., based upon quantitative data analysis), 2) conducted in the United States, 3) focused on FF, 4) that reported results on people's perceptions, attitudes, knowledge, or beliefs about FF or FFC, 5) included healthy people without disease, and 6) had a sample size ≥100.

Our study's exclusion criteria included: 1) review papers or qualitative research without structured data collection, 2) studies conducted outside the United States, 3) studies focused only on selected food groups (i.e., sugar-sweetened beverages, unhealthy snacks, or convenience foods), 4) absence of results on people's perceptions, attitudes, knowledge, or beliefs about FF or FFC, 5) participants having diet-related diseases, and 6) sample size <100.

Data extraction

We extracted information including study setting, study design and objective, sample characteristics (e.g., age, sex, sample size, race/ethnicity, sampling area, prevalence of overweight/obesity), FF definition in the study, level of FFC, assessment and level of attitudes, knowledge, beliefs, and perceptions of FF and its associations with FFC and obesity, while following PRISMA guidelines, into a standardized data extraction form. Two co-authors carried out the literature search and data extraction.

Study quality assessment

We modified the NIH quality assessment tool for observational cohort and cross-sectional studies ( 29 ) to assess the quality of each included study by 7 criteria according to the study characteristics. For each criterion, a score of 1 was assigned if “yes” was the response, whereas “0” was assigned otherwise (i.e., an answer of “no”, “not applicable”, “not reported”, or “cannot determine”). A study-specific global score, ranging from 0 to 7 (a higher score indicates a better rank than a lower score), was calculated by summing scores across all criteria. This quality assessment helped to describe the strength of the scientific evidence, but was not used to determine the inclusion of studies ( Supplemental Table 2 ).

Main characteristics of the included studies

Study design and quality.

From a pool of 13 studies, there was 1 longitudinal study and 12 cross-sectional studies. The cohort study collected information from paper questionnaires administered in person. Seven cross-sectional surveys were web-based or random-digit-dial telephone-based, whereas the remaining studies were conducted through intercept interviews at FF restaurants, colleges, and public health centers from the following states: California, Maryland, Minnesota, New Jersey, New York, North Carolina, Philadelphia, and South Carolina ( Table 1 ). The study quality assessment score ranged from 3 to 6 out of 7 ( Supplemental Tables 1 and 2 ). All studies included study samples of >100 participants [the smallest sample was 107 ( 30 ) and the largest 10,450 ( 31 )], and specified measures of FFC and FF-related knowledge, attitudes, beliefs, and perceptions.

Main characteristics of the 13 studies regarding Americans’ perceptions of fast food (FF) and FF consumption (FFC) 1

Participant characteristics

Demographics of study subjects were heterogeneous in the 13 studies. Two studies targeted children (<18 y) ( 17 , 32 ). The range of mean age in the 11 other studies was from 34.9 y to 57.6 y. Except for 1 study ( 33 ), the studies included both males and females. Five (42%) studies were race/ethnicity-based: 2 studies included mostly African-Americans and Latinos ( 34 , 35 ), 3 studies were specifically composed of African Americans ( 36 ), whites (94%) ( 37 ), or first-generation Mexican immigrant Latinos ( 33 ), whereas 8 studies (55%) had diverse race/ethnic groups ( 3 , 17 , 30 , 31 , 32 , 38 , 39 , 40 ).

Among the 6 studies reporting participants’ weight status, 1 study had all obese participants ( 38 ), and in the majority of the studies at least two-thirds of participants were either overweight or obese ( 33 , 34 , 36 , 38–40 ). Three studies reported data from low-SES populations ( 34 , 35 , 38 ). A single study collected data from public health clinic clients ( 34 ).

Definition of FF in the studies reviewed

FF refers to foods that are mass-produced and can be served quickly. They often provide lower nutritional value and higher sugar, fat, or sodium content compared with other dishes. In these studies, the most common definition of FF was foods derived from FF restaurants such as McDonald's, Pizza Hut, Burger King, Kentucky Fried Chicken, Taco Bell, Wendy's, and other similar establishments ( Table 1 ), unlike Piron and colleagues who focused solely on McDonald's ( 34 ). The consumption of FF was measured through various FFQs or 5-point Likert scales. Studies reported FFC with a frequency of 1 wk, 1 mo, 3 mo, or 1 y. Percentages or mean number of FF meals per week were reported [e.g., 50% of subjects ate FF 1–2 times/wk ( 32 ), having FF 1.0 time/wk on average ( 33 ), see Table 1 ].

Main research focus of the studies

The majority of the 13 studies investigated Americans’ psychosocial factors/personal preference in FF purchases ( 30 , 32 , 33 , 36 , 37 , 39 ) or perceived food environments ( 31 , 40 ), such as FF availability in the neighborhood. The link between weight loss attempts ( 38 ) and individuals’ health concerns about FF ( 3 , 17 ) with FFC were addressed in 3 studies. Two studies examined the association of nutrition knowledge [e.g., required daily calorie level ( 34 , 35 ) and FF calorie estimation ( 35 )] with FFC. No studies directly compared obesity risk by different FF perceptions ( Figure 2 ).

Number of fast food perception studies by research focus and study design. (A) Research focus. (B) Sampling pool. (C) Age group of study subjects.

Perceptions of FF

Interviews, questionnaires, and focus group discussions were used to assess perceptions of FF regarding beliefs, attitudes, and knowledge. A nationally representative survey (which included >2000 adults matched to national sociodemographic characteristics) reported that in 2003, 23% of Americans considered FF to be “good” (i.e., “very good” or “fairly good”), which did not change over 10 y. About two-thirds of Americans thought FF was “not good” (i.e., “not too good”, “not good at all”) in both 2003 and 2013, while the percentage who considered FF “not good at all” increased from 23% to 28% ( Figure 3 ) ( 3 ). One study directly measured adolescents’ beliefs about risks and benefits of eating FF in online panels using a 5-point Likert scale (range: 1–5). The mean score of adolescents’ reported experience of positive health consequences (e.g., feeling good) after eating at FF restaurants every day was 2.8 (SD: 1.1) and that for negative health consequences (e.g., harming their health) was 3.5 (SD: 1.2) ( 17 ).

Americans’ perception and consumption of fast food based on Gallup daily tracking survey in 2003, 2006, and 2013 (3). (A) Americans’ perception of fast food by year (%). (B) Americans’ frequency of eating fast food by year (%). (C) Americans’ perception of fast food by fast food consumption level in 2013 (%). Data source: Gallup daily tracking survey based on telephone interviews conducted in 2003, 2006, and 2013 with a random sample of >2000 adults (aged ≥18 y old) per wave, living in all 50 US states and the District of Columbia. The samples were weighted to match the national demographics of gender, age, race, Hispanic ethnicity, education, region, population density, and phone status (3). This is the best related study we identified that reported on Americans’ perceptions of FF, although it was not published in a peer-reviewed journal.

Seven studies examined reasons or personal factors for purchasing FF with multiple-choice or open-ended questions, regarding negative compared with positive attitudes/beliefs toward FF and related health concerns, such as 1) preferred convenience [e.g., I eat at FF restaurants because they are easy to get to, quick, no need to cook ( 37 ), fewer time barriers to FFC ( 32 ), I buy FF since it is convenient ( 30 ), and being not far away from home/work ( 33 )], 2) affordability [e.g., I eat at FF restaurants because they are inexpensive ( 37 ) and affordable with low price ( 33 , 36 ), I buy FF due to its amount of food for the money ( 30 )], 3) good taste [e.g., I buy FF since it is tasty ( 30 ), I have less taste barrier to FF vs. healthy foods ( 32 ), I'm not fully confident to eat less fat (56%) or keep healthy eating (40%) ( 36 )], 4) more fun and socializing opportunities than other eating places [e.g., I eat at FF restaurants because they are fun and entertaining, other people in my life chose to eat there; it is a way of socializing with friends or family ( 37 ), my child loves the kids’ menu and play area ( 33 , 39 )], and, on the other hand, 5) perceptions of FF as unhealthful [e.g., I think FF restaurants serve not good food for health ( 3 ), I think FF restaurants serve mostly high-fat foods or unsafe foods ( 37 ), I have concerns about health issues of FF ( 32 ), FF is bad for weight loss ( 38 )], etc. However, these studies were unable to fully document the diverse perspectives of Americans’ FF perceptions in the studies owing to the limitations of survey questionnaires.

People's perceptions of FF availability [high: 44% ( 40 )] and food environments (e.g., poor supermarket accessibility: 31.6%, poor grocery quality: 13.9%) ( 31 ), knowledge of daily caloric requirements [23% correctly answered ( 34 , 35 )], and estimation of FF calories [15% ( 35 )] were estimated with a Likert scale or open-ended questions ( Table 1 ).

Associations between FF perceptions, FFC, and obesity risk

No published studies examined the association between FF perception and obesity risk. Some reported on diverse associations between Americans’ perceptions of FF and FFC (see Table 2 ). Several salient points emerged regarding FF and obesity risk factors. First, an individual's positive attitudes about FF may associate with a high level of FFC. People had more frequent FF intake when they thought of FF as convenient (likelihood of FFC >1 time/wk, OR: 1.2; 95% CI: 1.1, 1.2 compared with not perceived as convenient) ( 37 ), and preferred having a kid's menu and play area [data were not shown, P  < 0.05 ( 33 )]. Americans who consumed less FF seemed more likely to view FF negatively. Those who ate FF least often (< a few times per year) were about 2 times more likely to report FF as “not good at all” than those who ate FF at least weekly (43% compared with 19%) ( 3 ). In addition, girls who reported barriers in time (per 1 SD change, OR: 1.18; 95% CI: 1.04, 1.34) ( 32 ) and taste (OR: 1.26; 95% CI: 1.11, 1.44) ( 32 ) to healthy eating compared with FF had more frequent consumption of FF than others. Having low self-efficacy to avoid fat or the unhealthfulness of FF were also predictors of frequent FF restaurant use [risk of more frequent FFC per 1 SD change of self-efficacy for healthy eating, OR: 0.80; 95% CI: 0.75, 0.98 ( 32 ); data were not shown, all P values <0.05 ( 36 )]. Those who attempted weight loss ate less FF [likelihood of weekly FFC, OR: 0.77, 95% CI: 0.62, 0.97 compared with not trying to lose weight ( 38 )], which indicated weight concerns surrounding FFC. However, health care provider's advice to lose weight among obese subjects was not associated with lower FFC (likelihood of weekly FFC, OR: 0.82; 95% CI: 0.66, 1.02) ( 38 ). In another study, neither ease of access nor fastness of FF had a significant association with FFC among Latina women ( 33 ).

The association between Americans’ perceptions of FF and FFC 1

Reported associations between beliefs about health consequences of FF and FFC were inconsistent by gender. One study reported that FFC was higher in individuals reporting positive perceptions about FF's impact on health [number of FFC days in the past month per perception score about the health benefit of FF, β ± SE = 0.23 ± 0.03, P  < 0.01 ( 17 )]. However, FFC did not differ by perceived health risks of FF ( P  > 0.05) in 2 cross-sectional studies among adolescents and adults ( 17 , 37 ), whereas the risk of more frequent FFC lowered with the degree of concern about health (per 1 SD change, OR: 0.83; 95% CI: 0.73, 0.95) among girls in a longitudinal study ( 32 ).

Nutrition knowledge could influence Americans’ FF perceptions and consumption. About four-fifths of FF restaurant users have an incorrect estimation of daily caloric requirements ( 34 , 35 ). On the other hand, the mandatory menu labeling in FF restaurants in New York City increased the correct estimation for FF calories among consumers in a low-income neighborhood by 60%, although the correct rate was still low (before menu labeling: 15%; after menu labeling: 24%) ( 35 ). The majority of individuals thought FF calorie labeling was important (93%), and that FF calorie information should be posted on the menu next to the food items (85%) ( 34 ).

Overall, the link between FFC, FF establishments, and other food restaurants/market options being reported seems inconsistent. One study reported higher FFC among those with a negative perception of the food environment, such as poor produce availability [among individuals nested in census tracts, incidence rate ratios (IRRs) of FFC, IRR: 1.31; 95% CI: 1.19, 1.45], supermarket accessibility (IRR: 1.06; 95% CI: 1.00, 1.11), and grocery quality (IRR: 1.20; 95% CI: 1.12, 1.28) around the neighborhood ( 31 ). However, another study found that neither personal perception of FF restaurants in neighborhoods (OR: 1.04; 95% CI: 0.73, 1.50) nor the Geographic Information System (GIS)-based presence of FF outlets within 1 mile of home (OR: 0.64; 95% CI: 0.38, 1.09) was associated with a higher weekly FFC ( 40 ).

Factors that might affect Americans’ FF perception and FFC

FF perceptions among obese individuals may be critical for diet behavior change and weight loss efforts. One study showed that obese adults attempting to lose weight consumed less FF than those not trying to lose weight (OR: 0.77; 95% CI: 0.62, 0.97) after adjusting for health care provider's advice to lose weight. However, health care provider's advice to lose weight had insignificant differences on obese individuals’ weekly FFC after adjusting for the respondent's weight loss attempts ( 38 ). These findings indicate that FFC was perceived as bad for weight loss among obese adults. It may be that receiving health care providers’ advice to lose weight is not associated with a further reduction in FFC among those who are trying to lose weight, as they already consume energy-dense foods less often. On the other hand, health care providers may not educate patients well about FF as a typical example of energy-dense food, since those having a health care provider's advice but no weight loss attempts did not show a significant difference in FFC in that study.

In addition, different levels of FFC across age, gender, and race/ethnicity may indicate demographic differences in FF perceptions. Most of the studies consistently found that the young ( 33 , 36 , 40 ) [young parents ( 39 )], males ( 32 , 37 , 41 ), African Americans and Hispanics ( 41 ), the employed ( 33 , 40 ), the unmarried ( 36 , 40 ), obese or physically inactive people ( 36 ), or people who were not attempting to lose weight ( 38 ) were more likely to have higher FFC (or ate more frequently in FF restaurants) than old, female, white, unemployed, married, non-obese, or physically active people or people who were attempting to lose weight. In contrast, 1 study found a higher likelihood of weekly FFC in white compared with African American, Hispanic, and other race/ethnic groups ( 40 ); but no significant sex difference in FFC among African Americans ( 36 ) ( Table 1 ).

Our systemic review found that only a relatively small number of studies ( n  = 13) have examined Americans’ perceptions of FF, and only 1 was a longitudinal study. Some of them assessed how Americans’ perceptions about FF might associate with FFC, but none examined whether or not Americans’ perceptions of FF affect obesity risk. Americans had both positive and negative beliefs and attitudes about FF. However, thus far, only 1 study has reported such specific results; and it was based on a phone survey. Future studies are needed in this field.

A 2013 nationally representative phone survey of about 2000 American adults found that about 22% of Americans considered FF good, whereas 28% thought FF was “not good at all” ( 3 ). The others (about 50%) thought FF was “not too good”. Some of these perceptions had significant associations with the level of FFC. Those who perceived FF as convenient and beneficial to health, preferred the taste of FF compared with healthy foods, or had low self-efficacy for eating less fat were more likely to frequently eat FF than their counterparts. Americans who consumed less FF seemed more likely to view FF negatively. However, inconsistent findings were shown in the association between perceived FF health risks and FFC. Perceived FF availability in neighborhoods was not associated with FFC.

Our systematic review found that Americans do not have good knowledge of FF calories, or daily caloric requirements ( 34 , 35 ). However, two-thirds of Americans thought the food served at FF restaurants is not good for them, and even 73% of weekly FF consumers did so ( 3 ). Nonetheless, Americans continue to consume FF and think of FF as one of their casual dining options ( 42 ). FF images on television and frequent exposures to FF may induce people to perceive FF more positively by appealing to the perceptions of low cost, good taste, and convenience and desensitizing viewers to the possible health risks of FF. One study found that heavy television viewers perceived more positive health consequences but fewer health risks of eating in a FF restaurant every day than others ( 17 ).

Furthermore, perceived health benefits of FF ( 17 ) were associated with higher FFC, although perceived health risks of FF did not result in a significant difference in FFC in 2 studies ( 17 , 37 ). One study concluded that educating the public about the health risks of FF may not bring either people's attention to or desired changes in dietary behavior ( 37 ). Not just the convenience, entertainment, and socializing opportunities of FF ( 32 , 33 , 37 ), but also Americans’ low self-efficacy to eat less fat and avoid the unhealthfulness of FF ( 32 ) may influence FFC. However, African Americans and Latina women did not take into account low price ( 36 ), easy access, and fastness of FF ( 33 ) when choosing a FF restaurant; instead the taste and familiarity of FF guided their choices.

Previous studies have noted that the presence of FF in the neighborhood was not associated with individuals’ FFC ( 43 , 44 ), although higher BMI was found among subjects living with FF restaurants in the neighborhood ( 40 ). Yet, 1 study found that FF outlet density in low-income neighborhoods was positively associated with FFC ( 45 ). The negative perception of other food environments (e.g., poor produce availability and supermarket accessibility, and poor grocery quality in the surrounding area) was also associated with greater FFC ( 31 ). We speculate that the conflicting research findings could be due to several reasons. First, methodological issues in Oexle and colleagues’ study ( 40 ), e.g., the conventional study design, examining a selective overweight/obese population, and not a using rigid boundary for FFC near the home, could have biased the findings. Second, individual perceptions and awareness of food environments are not fully captured by GIS-based data ( 31 , 46 ). Third, results may indicate that perceiving a short distance to FF availability in the neighborhood is not the major factor Americans use to decide their amount of FFC. Compared with others in developing countries who were exposed to FF later, Americans are less sensitive to nearby FF availability ( 47 ). Also Americans’ typical food shopping behaviors by car ( 48 ) may lead them to feel no barriers to visiting relatively faraway FF restaurants. A study found that Americans travel an average of 2.6 (SD: 3.7) miles from home to food establishments ( 49 ).

A longitudinal study in the United States reported that instead of FF availability, FF price had a significant effect on adolescents’ BMI ( 11 ). Another study reported that a 10% higher FF outlet density in the neighborhood indicated by zip code was associated with a 0.3% higher frequency of children's weekly FFC; but a 10% higher FF price resulted in 5.3% lower FFC (all P values <0.01) ( 41 ). Overweight/obese people can be more vulnerable to the FF availability in their neighborhood than others regarding their FFC ( 41 ). Only overweight/obese children had a sensitivity to FF availability (indicated by FF restaurant density) influencing their FFC compared with non-overweight children (β ± SE = 0.08 ± 0.03, P  < 0.01 compared with −0.40 ± 0.33, P  > 0.05) ( 41 ). Obese people may purchase more calories when they go to FF restaurants than non-overweight individuals do ( 41 ).

Future research is needed to confirm the association between perceived FF availability and FFC in the United States. Regulating accessibility of FF chains in the United States might not be as effective as raising FF price for obesity interventions ( 11 , 15 , 50 ), although the sustainable effects of health taxes on reducing consumption of targeted products and related harms are not known ( 51 ). Demonstrating quick and convenient preparation of nutritious alternatives (e.g., healthier prepacked meals) to FF ( 37 ) or providing restricted or guided choices in food outlets ( 52 ) could be more promising interventions for the obesity epidemic in the United States as shown in intervention studies.

Our reviewed research findings have several limitations. The quality of the studies reviewed was relatively low, e.g., predominately based on convenience sampling, local, cross-sectional, and race/ethnicity-based study designs, which may bias the results due to under/overrepresentation of certain groups. Also, the definition of FF used varied across the studies, and some of the studies did not directly measure FF perceptions. Cross-sectional data cannot assess causal relationships. None of the studies examined the association between FF perception and obesity risk.

Nevertheless, to our knowledge, our study is the first to systematically examine people's perception of FF and its association with FFC in the United States, and provides useful insight into obesity intervention strategies considering FF. To improve research into Americans’ FF perception and its impact on FFC, future studies should use longitudinal study designs with representative samples to examine the causal relationship between FF perceptions and FFC, and directly measure Americans’ perceptions regarding FF. For example, questions should assess whether Americans think FFC is good or bad for health and should be limited, or whether Americans think frequent FFC increases the risk of obesity and reducing FFC helps with weight loss. As shown here, perceptions may be more proximal drivers of FFC behavior than external factors, such as FF availability. For example, changing the perceived importance of calorie counts on menus for weight loss strategies may be needed to complement the environmental changes of posting the information. This would allow for the development of behavioral intervention strategies regarding food choice dictated by positive/negative perceptions, knowledge and attitude, and food environment/prices.

In conclusion, only a small number of studies have examined Americans’ perceptions of FF and their associations with FFC. None have examined how they might link to obesity risk. Americans have both negative and positive perceptions of FF, and are likely to purchase more FF as they valued the convenience and taste of FF, and preferred kid's menus and play areas in FF restaurants over other eating places. Those who consumed less FF seemed more likely to view FF negatively. Further studies with longitudinal study designs and standardized direct measures of FF perceptions are needed.

Supplementary Material

Supplement tables, acknowledgments.

We thank Linda Nguyen for her assistance in helping to conduct some related literature search. All authors have read and approved the final manuscript.

Supported in part by research grants from the US NIH (U54HD070725), the Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD, 1R01HD064685-01A1), the USDA Agricultural Research Service (3062-51000-051-00D), and the National Aeronautics and Space Administration (NASA) Mission X program. The content of the paper is solely the responsibility of the authors and does not necessarily represent the official views of the funders.

Author disclosures: JM, LJ, HX, JK, and YW, no conflicts of interest.

Supplemental Tables 1 and 2 are available from the “Supplementary data” link in the online posting of the article and from the same link in the online table of contents at https://academic.oup.com/advances/ .

Abbreviations used:

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• Published: 20 March 2024

On the value of food systems research

Nature Food volume  5 ,  page 183 ( 2024 ) Cite this article

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Every study has limitations; the question is whether it moves the field forward and what this entails for each community.

A great deal of research is exclusively assessed in terms of technical quality, a metric that is arguably easier to measure in exact than non-exact sciences and that doesn’t say much about the impact of the research results to society. Its relevance is therefore limited when it comes to food systems research, which involves social and cultural elements and is motivated by grand societal challenges such as the fight against hunger, poverty and climate change. Questions related to food security and the sustainability of food systems, no matter whether they are approached through a nutritional, environmental or socioeconomic lens, tend to involve a great deal of complexity and context specificity.

Given the above, a question we ought to ask when assessing a food systems study is whether it moves the field forward and offers a substantial contribution despite its limitations. Equally important is to ask whether these limitations are transparently laid out. Ideally, the study would have a well-defined analytical framework and discuss the potential implications of its main assumptions, particularly if they are likely to change conclusions in a significant way. The line that marks the divide between ‘substantial’ and ‘non-substantial’ or ‘significant’ and ‘non-significant’, as used above, is to be drawn by the relevant research community — and is bound to change over time, based on that community’s understanding of what is useful or insightful in light of the field’s uncertainties. In the scientific peer-review process, the feedback of reviewers — as representatives of the research community — is key to making such a call.

What makes a piece of research valuable when it comes to food systems isn’t necessarily its degree of technical advance, but rather the conceptual advance it represents and the potential impact associated with it. For instance, the angle through which a problem is addressed and how it is framed can yield arresting and important conclusions, even when calculation methodologies remain unaltered. This point is well illustrated by food-related greenhouse gas (GHG) emissions, which were traditionally reported for each sector (transport, energy, industry, and so on) and supply stage (production, processing, distribution, consumption and waste) separately but have been more recently combined under ‘systems emissions’. While their breakdown informs sectoral policies, the sum of all GHG emissions is needed for synergies and trade-offs to be properly identified and accounted for 1 . Besides, the global overview of emissions is crucial for creating awareness around the impact of food choices and catalysing mitigation action. The message that food systems are currently responsible for a third of all current anthropogenic GHG emissions 2 , so widely publicized, was determinant for food systems to be placed at the centre of the climate agenda and to receive due attention from world leaders.

A recently proposed food classification system based on the degree of food processing that has singled out ultra-processed foods (UPFs) 3 provides another interesting case for reflection on how to evaluate research. Some scientists were critical of this new categorization, arguing that processing in itself isn’t what makes a food item good or bad for people and the environment, and highlighting mixed evidence on the impact of UPFs on biochemical risk factors for disease 4 . Others found it extremely useful for eliciting the association between the consumption of UPFs and many of their distinctive characteristics, which are themselves harmful to human health (either directly, like high sugar and/or additive content, or indirectly, through shifts in consumers’ preferences towards impoverished diets) and the environment. Undeniably, this classification has stimulated a healthy debate around modern dietary habits, the intricate factors behind them, and public policies’ sole focus on nutritional characteristics of foods.

As the examples above suggest, two more points deserve attention when thinking of the value — and contribution — of food systems research. The first point is about clarity over what a study can and cannot answer, and consequently what it should be used for. The combined account of food-related GHG emissions sheds light on food systems’ total footprint, underscoring the need for coordinated policies, but doesn’t replace sectoral granularity. Likewise, a food classification system based on UPFs may not say much about processing as a food engineering technique, yet it highlights important issues surrounding these products. The second point refers to the scope of the analysis and the multiplicity of aspects that are considered given the urgency of food systems transformation. Whether that’s done in a meaningful way and to a sufficient extent is for the food community to judge.

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Title: What These Class of 2024 Graduating Seniors Will Miss Most About Georgetown

In the coming days, Georgetown will celebrate Hoyas in the Class of 2024 as they earn their degrees.

As these students prepare to graduate, many of them will remember the lifelong friendships, treasured lessons and favorite memories long after they’ve flipped their graduation tassels. Ingrained in every Georgetown experience are those little moments that make a deep impression, from random conversations in Lau with friends to a daily morning stroll under Healy Hall and countless hours of studying in the library.

We asked the seniors behind Georgetown Stories about those little moments and what they’ll miss the most about Georgetown. Here’s what the soon-to-be graduates said.

Countless Hours in Leo’s

Ava Culoso (C’24) 

I’ve been off the Georgetown meal plan for a year now, and even though I found ways to complain about the dining hall my sophomore and junior year, some of my fondest memories in college happened while sitting with my friends. We would turn hopes of “quick dinners” into hours of chatting. It always seemed whenever we had the most work, we would sit in Leo’s after we finished eating, just talking and laughing and losing track of time. 

I still have dinners with my roommates in my off-campus house, but nothing compares to the many nights when Leo’s dinner ended up being over two hours long. When I graduate and leave Georgetown, what I’ll remember are those conversations about nothing that somehow meant everything to me. 

Daily Joys on the Hilltop

Renato Llontop Calosi (SFS’24)

Waking up to the sight of beautiful Healy Hall right outside my window, walking to Leo’s for breakfast and greeting Suru — the front desk worker at Leo’s — working out early with all my roommates, and having bagels with Chaplain Michelle are just some of the daily joys that make Georgetown special. From greeting many students while walking around campus to making a new friend in class every day, there’s nothing more meaningful than savoring the graces we’ve received here. 

One of the things I’ll miss most is engaging in fascinating conversations about faith, culture, politics or simply Georgetown events with faculty and friends. Visiting our sacred spaces on campus, especially Dahlgren Chapel on Sundays, and chatting with our wonderful Campus Ministry staff — “God’s Squad” — are among those little things that truly make Georgetown so unique. As a campus tour guide since freshman year, I’ll miss showing our home to prospective students and their families. But I know for sure that every time I return, I’ll fall in love with this place all over again.

I know for sure that every time I return, I’ll fall in love with this place all over again. Renato Llontop Calosi (SFS’24)

Blissful Laundry Days

Christine Mauvais (N’24) 

It’s Sunday morning. The light is hitting my eyes, and I wake up to the natural rhythm of my own body instead of a bothersome ringtone. I roll around in my white comforter as I take in the scene of my room. My hamper is stuffed to the brim, reminding me that it’s laundry day. This means that I will dedicate the rest of my day  to only one task, and then follow suit with relaxation. 

I spent most of my laundry days “rotting” away while catching up on my dramas or New York Times crossword puzzles. The naps I had on that twin-sized bed were when I had the best hours of rest. It’s something about a full day of leisure that wraps up an exhausting school week and kicks off an upcoming exciting one. 

I will miss those moments of bliss. Even when I return home, my Sundays don’t hit as much as they do at Georgetown. I don’t know if it’s the mattress or the college air, but there’s something special about my lazy laundry days on the Hilltop. It will truly be missed!

The Hunt for Free Food

Maliha Kahn (SFS’24)

It’s been nearly a week since I graduated from Georgetown University in Qatar, and there are so many small things that made the last four years memorable. The city does not feel the same without the familiar routine of waking up and taking a tram to the campus. I miss the rush of running to the tram station knowing I’m already late yet managing to catch the tram just before it leaves (on good days). Visiting the atrium made me realize how much I miss the bustling noise and chaos. No matter how lonely I felt, all I needed to do was to step into the atrium and I’d feel at home. I’ll miss the many events that happened simultaneously and being mad at having to miss some.

The epitome of college life was scouring campus for events solely for the free food with my friends. Every now and then we’d stumble upon an event hosted by the dean’s office and then comment on how fancy the food and tiny hors d’oeuvres were. Even better were the midnight snacks from the vending machine when we pulled late nights at the library. I’ll miss my beloved couch, my faithful companion for studying and deep sleep.

Late Night Lau Study Breaks

Zehra Mizra (C’24)

I’m going to miss all the nights in Lau 2 (the 2nd floor of Lauinger Library) when I figured the presence of my friends would help me get work done. It may have helped me achieve about 20% more studying than I would’ve done if studying by myself, as we always got caught up talking to each other, seeing other classmates and friends and chatting with them, and taking study breaks to get a snack or coffee from the Midnight Mug coffee shop.

I am going to miss enjoying the first snowfall of the year on the Hilltop and watching my friends from warmer hometowns be fascinated by the snow, and find any material to sled down our small hills on campus, from extra mattresses to Adirondack chairs and cardboard boxes. 

I am going to miss the joy in the air as soon as the air starts to get warm after the winter and you see herds of students flock to the front lawn to have picnics, hammock, play spikeball and just sit outside and enjoy the weather despite being in the midst of midterms. 

Around-the-World Roommate Dinner Parties

Alara Karahan (SFS’24)

I’ll miss walking up the stairs next to Lau and seeing the towering Healy clock come into view. I’ll miss wandering past Corp spots, ears tuned for new songs to add to my playlist. I’ll miss seeing the familiar faces at Yates and silently acknowledging the shared misery of a treadmill workout. 

I’ll miss themed roommate dinner parties that take us from Argentinian alfajores to Hyderabadi biryani. I’ll miss wearing florals on Farmers Market Wednesdays and sunbathing under Copley’s “tree of life.” I’ll miss my friends spam-calling me whenever they spot Jack and dropping everything to go see him. I’ll miss doing my world tour on the library’s “social floor,” procrastinating by making small talk with every person I’ve ever encountered over four years. 

I’ll miss post-class debates with a professor because the hour and 15 minutes just wasn’t enough time. I’ll miss attending events in DC with big-name politicians and professionals and proudly telling them I attend Georgetown. I’ll miss watching my friends lead organizations that invest millions for the alumni association, organize tours for the 55,000 annual campus visitors, or run the world’s largest student-run nonprofit. 

Amidst these goodbyes, there’s one thing that’s true for all of us — we’ll always be Hoyas.

Celebrate the Class of 2024

Meet the class of 2024: the must-read stories from georgetown’s graduating seniors.

The Best Spots for Graduation Photos at Georgetown University

No Longer First-Gen: A Mother and Daughter Graduate From College at the Same Time

The graduating senior, journalist who once (or twice) skipped class to cover biden at the white house.

The Soon-to-Be SFS Grad Ready to Start a Career in Conflict Mediation in the Middle East

How This Graduating Senior Uses Public Health Research to Improve Lives Around the World