research on gmo foods

What’s the latest on GMOs and gene-edited foods – and what are the concerns? An expert explains

Research Fellow, Centre for Crop Science, The University of Queensland

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Karen Massel does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

University of Queensland provides funding as a member of The Conversation AU.

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Advances in genetic engineering have given rise to an era of foods – including genetically modified organisms (GMOs) and gene-edited foods – that promise to revolutionise the way we eat.

Critics argue these foods could pose risks to human health and the environment. Proponents point to their potential for enhancing yields, reducing food waste, and even combating climate change.

What are GMOs and gene-edited foods? And how are they shaping the future of our food systems?

GMOs and gene-edited foods aren’t the same

GMOs are organisms whose genetic material has been artificially altered by inserting a piece of foreign DNA. This DNA may be synthetic in origin or sourced from other organisms.

Gene editing involves making precise changes to an organism’s genome without the integration of foreign DNA elements. Using techniques such as CRISPR/Cas, scientists make precise “cuts” in the DNA to create new genetic variation. Unlike with GMOs, this introduces only minor modifications, which are indistinguishable from natural mutations.

Although GMOs and gene-edited foods have been in circulation for almost three decades, research in this space continues to deliver breakthroughs. These technologies are being applied to provide a range of benefits, from improved nutrition in food, to reduced food waste and increased crop tolerance against climate stresses.

Read more: What is CRISPR, the gene editing technology that won the Chemistry Nobel prize?

What are the concerns?

The major criticisms of GMOs are related to the overuse of specific herbicides.

GMOs are mainly used to produce crops that are herbicide-resistant or produce pesticides. Farmers can then use herbicides on those crops to control weeds more effectively, without the plants themselves dying. This leads to higher yields on less land, and often with less chemicals used overall.

However, these crops rely on the use of said lab-made chemicals . And although the government regulates them, ethical and safety debates continue. People raise concerns over potential long-term health impacts, impacts on biodiversity and ecosystems, and the increased corporate control over agriculture.

Concerns generally aren’t related to the actual manipulation of the plants’ DNA.

Is genetic modification itself unsafe?

When it comes to the food we eat, how much do we really know about its DNA? Even among experts with genome-sequencing information, most have only one or a few sequenced “reference” varieties, and these often aren’t the same as the plants we eat.

The fact is, we don’t really understand the genomes of many plants and animals we eat. So there’s no reason to suggest tweaking their gene sequences will make consumption harmful. Moreover, there’s currently no evidence regulator-approved GMOs or gene-edited foods aren’t safe for human consumption.

In regards to food safety, one valid concern would be the potential creation of new allergens: proteins within the crop the body recognises and creates an immune response to.

But it’s important to remember many foods we eat are already allergenic. Common examples include wheat, peanuts, soy, milk and eggs. Some common foods are even toxic if consumed in large quantities or without appropriate preparation, such as rhubarb leaves, raw cassava, raw kidney beans and raw cashews.

Ironically, researchers are using gene editing to work towards eliminating proteins that cause allergies and intolerances. Gluten-free wheat is one example.

GMOs and gene-edited foods are widespread

Due to inconsistent rules about labelling GMOs and gene-edited foods around the world, many consumers may not realise they’re already eating them.

For example, the most widely used enzyme in cheese-making, rennet , is produced from a GMO bacterium. GMO microbial rennet produces a specific enzyme called chymosin, which helps coagulate milk and form curds. Historically, chymosin was extracted from young cow stomachs, but in the 1990s scientists managed to genetically engineer a bacterium to synthesise it.

GMOs and gene-edited cereal and oilseed products are also widely used in stockfeeds. There is ongoing research to improve feed through enhanced nutrition , and produce crops that will decrease methane emissions from cattle .

When it comes to modifying animals themselves, ethical considerations must be balanced alongside potential benefits.

In Australia, about 70% of cattle are genetically polled (hornless). Having polled cows improves meat quality through less injury to meat, and is considered better for animal welfare. In the US, fast-growing genetically modified salmon has been approved for consumption.

In a horticultural context, the genetically modified rainbow papaya stands out. It was developed in the late 1990s in response to a ringspot virus outbreak that nearly wiped out the global papaya industry. Researchers created the virus-resistant “transgenic” papaya, which now makes up a significant proportion of papayas consumed.

In terms of boosting nutritional content, “ golden rice ” biofortified with Vitamin A (GMO) is being cultivated in the Philippines, as are tomatoes biofortified with Vitamin D (GE) in the United Kingdom, and GABA-enriched tomatoes (GE) in Japan.

Research is also being done to create non-browning mushrooms , apples and potatoes. A simple gene edit can help inhibit the browning oxidation reaction, leading to a longer shelf-life and less food waste.

Regulation in Australia and New Zealand

So why don’t you see non-browning mushrooms at your local supermarket?

In Australia, the Office of the Gene Technology Regulator regulates GMOs. It has approved four GMO crops for cultivation: cotton, canola, safflower and Indian mustard. However, many more are imported for food ingredients (including modified soy, cottonseed oil, corn and sugar beet) and stockfeed (canola, maize and soy).

Gene-edited food crops can be cultivated without any regulatory restrictions or labelling in Australia. The Gene Technology Act 2000 deregulated these products in 2019.

On the other hand, New Zealand’s Environmental Protection Authority has maintained regulatory restrictions on both gene-edited foods and GMOs. Divergent definitions have led the bi-national agency Food Standards Australia New Zealand (FSANZ) to adopt a cautious approach, regulating gene-edited foods and feeds as GMOs.

The lack of alignment in definitions in Australian has confused producers and consumers alike. FSANZ has said it will continue to monitor developments in gene-editing technology, and will consider reviewing its regulatory approach.

Responsible research

Both GMOs and gene-edited foods offer great promise. Of course there are valid concerns, such as the potential to create new allergens, unintended consequences for ecosystems, and growing corporate control over food. But these can be addressed through responsible research and regulatory frameworks.

Ultimately, the development of future foods must be guided by a commitment to sustainability, social justice and scientific rigour.

Correction: This article previously said the transgenic rainbow papaya made up the majority of papayas consumed worldwide. This was incorrect and the wording has been amended.

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Food, genetically modified

These questions and answers have been prepared by WHO in response to questions and concerns from WHO Member State Governments with regard to the nature and safety of genetically modified food.

Genetically modified organisms (GMOs) can be defined as organisms (i.e. plants, animals or microorganisms) in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination. The technology is often called “modern biotechnology” or “gene technology”, sometimes also “recombinant DNA technology” or “genetic engineering”. It allows selected individual genes to be transferred from one organism into another, also between nonrelated species. Foods produced from or using GM organisms are often referred to as GM foods.

GM foods are developed – and marketed – because there is some perceived advantage either to the producer or consumer of these foods. This is meant to translate into a product with a lower price, greater benefit (in terms of durability or nutritional value) or both. Initially GM seed developers wanted their products to be accepted by producers and have concentrated on innovations that bring direct benefit to farmers (and the food industry generally).

One of the objectives for developing plants based on GM organisms is to improve crop protection. The GM crops currently on the market are mainly aimed at an increased level of crop protection through the introduction of resistance against plant diseases caused by insects or viruses or through increased tolerance towards herbicides.

Resistance against insects is achieved by incorporating into the food plant the gene for toxin production from the bacterium Bacillus thuringiensis (Bt). This toxin is currently used as a conventional insecticide in agriculture and is safe for human consumption. GM crops that inherently produce this toxin have been shown to require lower quantities of insecticides in specific situations, e.g. where pest pressure is high. Virus resistance is achieved through the introduction of a gene from certain viruses which cause disease in plants. Virus resistance makes plants less susceptible to diseases caused by such viruses, resulting in higher crop yields.

Herbicide tolerance is achieved through the introduction of a gene from a bacterium conveying resistance to some herbicides. In situations where weed pressure is high, the use of such crops has resulted in a reduction in the quantity of the herbicides used.

Generally consumers consider that conventional foods (that have an established record of safe consumption over the history) are safe. Whenever novel varieties of organisms for food use are developed using the traditional breeding methods that had existed before the introduction of gene technology, some of the characteristics of organisms may be altered, either in a positive or a negative way. National food authorities may be called upon to examine the safety of such conventional foods obtained from novel varieties of organisms, but this is not always the case.

In contrast, most national authorities consider that specific assessments are necessary for GM foods. Specific systems have been set up for the rigorous evaluation of GM organisms and GM foods relative to both human health and the environment. Similar evaluations are generally not performed for conventional foods. Hence there currently exists a significant difference in the evaluation process prior to marketing for these two groups of food.

The WHO Department of Food Safety and Zoonoses aims at assisting national authorities in the identification of foods that should be subject to risk assessment and to recommend appropriate approaches to safety assessment. Should national authorities decide to conduct safety assessment of GM organisms, WHO recommends the use of Codex Alimentarius guidelines (See the answer to Question 11 below).

The safety assessment of GM foods generally focuses on: (a) direct health effects (toxicity), (b) potential to provoke allergic reaction (allergenicity); (c) specific components thought to have nutritional or toxic properties; (d) the stability of the inserted gene; (e) nutritional effects associated with genetic modification; and (f) any unintended effects which could result from the gene insertion.

While theoretical discussions have covered a broad range of aspects, the three main issues debated are the potentials to provoke allergic reaction (allergenicity), gene transfer and outcrossing.

Allergenicity

As a matter of principle, the transfer of genes from commonly allergenic organisms to non-allergic organisms is discouraged unless it can be demonstrated that the protein product of the transferred gene is not allergenic. While foods developed using traditional breeding methods are not generally tested for allergenicity, protocols for the testing of GM foods have been evaluated by the Food and Agriculture Organization of the United Nations (FAO) and WHO. No allergic effects have been found relative to GM foods currently on the market.

Gene transfer

Gene transfer from GM foods to cells of the body or to bacteria in the gastrointestinal tract would cause concern if the transferred genetic material adversely affects human health. This would be particularly relevant if antibiotic resistance genes, used as markers when creating GMOs, were to be transferred. Although the probability of transfer is low, the use of gene transfer technology that does not involve antibiotic resistance genes is encouraged.

Outcrossing

The migration of genes from GM plants into conventional crops or related species in the wild (referred to as “outcrossing”), as well as the mixing of crops derived from conventional seeds with GM crops, may have an indirect effect on food safety and food security. Cases have been reported where GM crops approved for animal feed or industrial use were detected at low levels in the products intended for human consumption. Several countries have adopted strategies to reduce mixing, including a clear separation of the fields within which GM crops and conventional crops are grown.

Environmental risk assessments cover both the GMO concerned and the potential receiving environment. The assessment process includes evaluation of the characteristics of the GMO and its effect and stability in the environment, combined with ecological characteristics of the environment in which the introduction will take place. The assessment also includes unintended effects which could result from the insertion of the new gene.

Issues of concern include: the capability of the GMO to escape and potentially introduce the engineered genes into wild populations; the persistence of the gene after the GMO has been harvested; the susceptibility of non-target organisms (e.g. insects which are not pests) to the gene product; the stability of the gene; the reduction in the spectrum of other plants including loss of biodiversity; and increased use of chemicals in agriculture. The environmental safety aspects of GM crops vary considerably according to local conditions.

Different GM organisms include different genes inserted in different ways. This means that individual GM foods and their safety should be assessed on a case-by-case basis and that it is not possible to make general statements on the safety of all GM foods.

GM foods currently available on the international market have passed safety assessments and are not likely to present risks for human health. In addition, no effects on human health have been shown as a result of the consumption of such foods by the general population in the countries where they have been approved. Continuous application of safety assessments based on the Codex Alimentarius principles and, where appropriate, adequate post market monitoring, should form the basis for ensuring the safety of GM foods.

The way governments have regulated GM foods varies. In some countries GM foods are not yet regulated. Countries which have legislation in place focus primarily on assessment of risks for consumer health. Countries which have regulatory provisions for GM foods usually also regulate GMOs in general, taking into account health and environmental risks, as well as control- and trade-related issues (such as potential testing and labelling regimes). In view of the dynamics of the debate on GM foods, legislation is likely to continue to evolve.

GM crops available on the international market today have been designed using one of three basic traits: resistance to insect damage; resistance to viral infections; and tolerance towards certain herbicides. GM crops with higher nutrient content (e.g. soybeans increased oleic acid) have been also studied recently.

The Codex Alimentarius Commission (Codex) is the joint FAO/WHO intergovernmental body responsible for developing the standards, codes of practice, guidelines and recommendations that constitute the Codex Alimentarius, meaning the international food code. Codex developed principles for the human health risk analysis of GM foods in 2003.

Principles for the risk analysis of foods derived from modern biotechnology

The premise of these principles sets out a premarket assessment, performed on a caseby- case basis and including an evaluation of both direct effects (from the inserted gene) and unintended effects (that may arise as a consequence of insertion of the new gene) Codex also developed three Guidelines:

Guideline for the conduct of food safety assessment of foods derived from recombinant-DNA plants

Guideline for the conduct of food safety assessment of foods produced using recombinant-DNA microorganisms

Guideline for the conduct of food safety assessment of foods derived from recombinant-DNA animals

Codex principles do not have a binding effect on national legislation, but are referred to specifically in the Agreement on the Application of Sanitary and Phytosanitary Measures of the World Trade Organization (SPS Agreement), and WTO Members are encouraged to harmonize national standards with Codex standards. If trading partners have the same or similar mechanisms for the safety assessment of GM foods, the possibility that one product is approved in one country but rejected in another becomes smaller.

The Cartagena Protocol on Biosafety, an environmental treaty legally binding for its Parties which took effect in 2003, regulates transboundary movements of Living Modified Organisms (LMOs). GM foods are within the scope of the Protocol only if they contain LMOs that are capable of transferring or replicating genetic material. The cornerstone of the Protocol is a requirement that exporters seek consent from importers before the first shipment of LMOs intended for release into the environment.

The GM products that are currently on the international market have all passed safety assessments conducted by national authorities. These different assessments in general follow the same basic principles, including an assessment of environmental and human health risk. The food safety assessment is usually based on Codex documents.

Since the first introduction on the market in the mid-1990s of a major GM food (herbicide-resistant soybeans), there has been concern about such food among politicians, activists and consumers, especially in Europe. Several factors are involved. In the late 1980s – early 1990s, the results of decades of molecular research reached the public domain. Until that time, consumers were generally not very aware of the potential of this research. In the case of food, consumers started to wonder about safety because they perceive that modern biotechnology is leading to the creation of new species.

Consumers frequently ask, “what is in it for me?”. Where medicines are concerned, many consumers more readily accept biotechnology as beneficial for their health (e.g. vaccines, medicines with improved treatment potential or increased safety). In the case of the first GM foods introduced onto the European market, the products were of no apparent direct benefit to consumers (not significantly cheaper, no increased shelflife, no better taste). The potential for GM seeds to result in bigger yields per cultivated area should lead to lower prices. However, public attention has focused on the risk side of the risk-benefit equation, often without distinguishing between potential environmental impacts and public health effects of GMOs.

Consumer confidence in the safety of food supplies in Europe has decreased significantly as a result of a number of food scares that took place in the second half of the 1990s that are unrelated to GM foods. This has also had an impact on discussions about the acceptability of GM foods. Consumers have questioned the validity of risk assessments, both with regard to consumer health and environmental risks, focusing in particular on long-term effects. Other topics debated by consumer organizations have included allergenicity and antimicrobial resistance. Consumer concerns have triggered a discussion on the desirability of labelling GM foods, allowing for an informed choice of consumers.

The release of GMOs into the environment and the marketing of GM foods have resulted in a public debate in many parts of the world. This debate is likely to continue, probably in the broader context of other uses of biotechnology (e.g. in human medicine) and their consequences for human societies. Even though the issues under debate are usually very similar (costs and benefits, safety issues), the outcome of the debate differs from country to country. On issues such as labelling and traceability of GM foods as a way to address consumer preferences, there is no worldwide consensus to date. Despite the lack of consensus on these topics, the Codex Alimentarius Commission has made significant progress and developed Codex texts relevant to labelling of foods derived from modern biotechnology in 2011 to ensure consistency on any approach on labelling implemented by Codex members with already adopted Codex provisions.

Depending on the region of the world, people often have different attitudes to food. In addition to nutritional value, food often has societal and historical connotations, and in some instances may have religious importance. Technological modification of food and food production may evoke a negative response among consumers, especially in the absence of sound risk communication on risk assessment efforts and cost/benefit evaluations.

Yes, intellectual property rights are likely to be an element in the debate on GM foods, with an impact on the rights of farmers. In the FAO/WHO expert consultation in 2003 , WHO and FAO have considered potential problems of the technological divide and the unbalanced distribution of benefits and risks between developed and developing countries and the problem often becomes even more acute through the existence of intellectual property rights and patenting that places an advantage on the strongholds of scientific and technological expertise. Such considerations are likely to also affect the debate on GM foods.

Certain groups are concerned about what they consider to be an undesirable level of control of seed markets by a few chemical companies. Sustainable agriculture and biodiversity benefit most from the use of a rich variety of crops, both in terms of good crop protection practices as well as from the perspective of society at large and the values attached to food. These groups fear that as a result of the interest of the chemical industry in seed markets, the range of varieties used by farmers may be reduced mainly to GM crops. This would impact on the food basket of a society as well as in the long run on crop protection (for example, with the development of resistance against insect pests and tolerance of certain herbicides). The exclusive use of herbicide-tolerant GM crops would also make the farmer dependent on these chemicals. These groups fear a dominant position of the chemical industry in agricultural development, a trend which they do not consider to be sustainable.

Future GM organisms are likely to include plants with improved resistance against plant disease or drought, crops with increased nutrient levels, fish species with enhanced growth characteristics. For non-food use, they may include plants or animals producing pharmaceutically important proteins such as new vaccines.

WHO has been taking an active role in relation to GM foods, primarily for two reasons:

on the grounds that public health could benefit from the potential of biotechnology, for example, from an increase in the nutrient content of foods, decreased allergenicity and more efficient and/or sustainable food production; and

based on the need to examine the potential negative effects on human health of the consumption of food produced through genetic modification in order to protect public health. Modern technologies should be thoroughly evaluated if they are to constitute a true improvement in the way food is produced.

WHO, together with FAO, has convened several expert consultations on the evaluation of GM foods and provided technical advice for the Codex Alimentarius Commission which was fed into the Codex Guidelines on safety assessment of GM foods. WHO will keep paying due attention to the safety of GM foods from the view of public health protection, in close collaboration with FAO and other international bodies.

Food, Genetically modified

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GMO Crops, Animal Food, and Beyond

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Am I eating foods that come from GMO crops?

It is very likely you are eating foods and food products that are made with ingredients that come from GMO crops. Many GMO crops are used to make ingredients that Americans eat such as cornstarch, corn syrup, corn oil, soybean oil, canola oil, or granulated sugar. A few fresh fruit and vegetables are available in GMO varieties, including potatoes, summer squash, apples, papayas, and pink pineapples. Although GMOs are in a lot of the foods we eat, most of the GMO crops grown in the United States are used for animal food.

To make it easier for consumers to know if the foods they eat contain GMO ingredients, the U.S. Department of Agriculture maintains a list of bioengineered foods available throughout the world. Additionally, you will start seeing the “bioengineered” label on some of the foods we eat because of the new National Bioengineered Food Disclosure Standard .

GMOs, Farm to Table

Where can you find gmos.

GMO Crops in the U.S.

What GMO crops are in the United States?

Only a few types of GMO crops are grown in the United States, but some of these GMOs make up a large percentage of the crop grown (e.g., soybeans, corn, sugar beets, canola, and cotton).

In 2020 , GMO soybeans made up 94% of all soybeans planted, GMO cotton made up 96% of all cotton planted, and 92% of corn planted was GMO corn.

In 2013 , GMO canola made up 95% of canola planted while GMO sugar beets made up 99.9% of all sugar beets harvested.

Most GMO plants are used to make ingredients that are then used in other food products. For example, cornstarch can be made with GMO corn and sugar can be made with GMO sugar beets.

Corn is the most commonly grown crop in the United States, and most of it is GMO. Most GMO corn is created to resist insect pests or tolerate herbicides. Bacillus thuringiensis (Bt) corn is a GMO corn that produces proteins that are toxic to certain insect pests but not to humans, pets, livestock, or other animals. These are the same types of proteins that organic farmers use to control insect pests, and they do not harm beneficial insects, such as ladybugs. GMO Bt corn reduces the need for spraying insecticides while still preventing insect damage. While a lot of GMO corn goes into processed foods and drinks, most of it is used to feed livestock, like cows, and poultry, like chickens.

Most soy grown in the United States is GMO soy. Most GMO soy is used for food for animals, predominantly poultry and livestock, and making soybean oil. It is also used as ingredients (lecithin, emulsifiers, and proteins) in processed foods.

GMO cotton was created to be resistant to bollworms and helped revive the Alabama cotton industry. GMO cotton not only provides a reliable source of cotton for the textile industry, it is also used to make cottonseed oil, which is used in packaged foods and in many restaurants for frying. GMO cottonseed meal and hulls are also used in food for animals.

Some GMO potatoes were developed to resist insect pests and disease. In addition, some GMO potato varieties have been developed to resist bruising and browning that can occur when potatoes are packaged, stored, and transported, or even cut in your kitchen. While browning does not change the quality of the potato, it often leads to food being unnecessarily thrown away because people mistakenly believe browned food is spoiled.

By the 1990s, ringspot virus disease had nearly wiped out Hawaii’s papaya crop, and in the process almost destroyed the papaya industry in Hawaii. A GMO papaya , named the Rainbow papaya, was created to resist ringspot virus. This GMO saved papaya farming on the Hawaiian Islands.

Summer Squash:

GMO summer squash is resistant to some plant viruses. Squash was one of the first GMOs on the market, but it is not widely grown.

GMO canola is used mostly to make cooking oil and margarine. Canola seed meal can also be used in food for animals. Canola oil is used in many packaged foods to improve food consistency. Most GMO canola is resistant to herbicides and helps farmers to more easily control weeds in their fields.

GMO alfalfa is primarily used to feed cattle—mostly dairy cows. Most GMO alfalfa is resistant to herbicides, allowing farmers to spray the crops to protect them against destructive weeds that can reduce alfalfa production and lower the nutritional quality of the hay.

A few varieties of GMO apples were developed to resist browning after being cut. This helps cut down on food waste, as many consumers think brown apples are spoiled.

Sugar Beet:

Sugar beets are used to make granulated sugar. More than half the granulated sugar packaged for grocery store shelves is made from GMO sugar beets. Because GMO sugar beets are resistant to herbicides, growing GMO sugar beets helps farmers control weeds in their fields.

Pink Pineapple:

The GMO pink pineapple was developed to have pink flesh by increasing the levels of lycopene. Lycopene is naturally found in pineapples, and it is the pigment that makes tomatoes red and watermelons pink.

What about animals that eat food made from GMO crops?

More than 95% of animals used for meat and dairy in the United States eat GMO crops. Independent studies show that there is no difference in how GMO and non-GMO foods affect the health and safety of animals. The DNA in the GMO food does not transfer to the animal that eats it. This means that animals that eat GMO food do not turn into GMOs. If it did, an animal would have the DNA of any food it ate, GMO or not. In other words, cows do not become the grass they eat and chickens don’t become the corn they eat.

Similarly, the DNA from GMO animal food does not make it into the meat, eggs, or milk from the animal. Research shows that foods like eggs, dairy products, and meat that come from animals that eat GMO food are equal in nutritional value, safety, and quality to foods made from animals that eat only non-GMO food.

Learn more about GMO Crops and Food for Animals .

Who makes sure animal food is safe?

The U.S. Food and Drug Administration (FDA) is the primary regulatory agency responsible for ensuring the safety of GMO and non-GMO food for animals. The FDA Center for Veterinary Medicine manages this responsibility. FDA requires that all food for animals, like food for human foods, be safe for animals to eat, be produced under clean conditions, contain no harmful substances, and be accurately labeled.

Are there GMO animals in the food supply?

Yes. FDA has approved an application allowing the sale of the AquAdvantage Salmon to consumers. The AquAdvantage Salmon has been genetically modified to reach an important growth point faster. FDA has also approved an alteration in the GalSafe pig for human food consumption and potential therapeutic uses. The GalSafe pig was developed to be free of detectable alpha-gal sugar on its cell surfaces. People with Alpha-gal syndrome (AGS) may have allergic reactions to alpha-gal sugar found in red meat (e.g., beef, pork, and lamb). FDA has determined that food from the AquAdvantage Salmon and the GalSafe pig are as safe and nutritious to eat as food from non-GMO salmon and pigs.

Are GMOs used to make anything besides food?

When you hear the term “GMO” you probably think of food. However, techniques used to create GMOs are important in creating some medicines as well. In fact, genetic engineering, which is the process used to create GMOs, was first used to make human insulin, a medicine used to treat diabetes. Medicines developed through genetic engineering go through an in-depth FDA approval process. All medicines must be proven to be safe and effective before they are approved for human use. GMOs are also used in the textile industry. Some GMO cotton plants are used to create cotton fiber that is then used to make fabric for clothing and other materials.

How GMOs Are Regulated in the United States

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College of Agriculture, Health and Natural Resources

Science of GMOs

Gmos and food safety.

Food products which are developed via Genetically Modified Organisms (GMOs) are widely distributed in the U.S. food supply. In addition, new products are being approved for use as techniques are developed and new uses for GMOs are considered. Biotech/GMO derived foods currently in use include corn used in milled corn products; soy used in milled soy products such as soybean oil and textured soy protein; animal feeds; and sugar beets. In addition, the Arctic apple (resists browning) and GMO Salmon have been recently approved as “safe” by the U.S. Food and Drug Administration (FDA).

The safety of Genetically Modified Organisms (GMO) has been debated almost since the phrase was attributed to the development of antibiotic resistant tobacco in 1983. Consumers continue to be concerned about both the food safety and the nutritional equivalence of GMO foods. In a 2015 Pew Research Center survey of consumers, 57% of adults believe that eating GMO foods is unsafe, while 37% say they believe it is generally safe.

Yet, science continues to suggest that there is no substantiated evidence that GMO foods are less safe than non-GMO derived food products. A 2016 report from the National Academies of Science, Genetically Engineered Crops:  Experiences and Prospects discusses effects on human health. Claims regarding human health and safety of GMO foods included increased risks from cancers, kidney disease, obesity, celiac disease, diabetes and allergies. When comparing rates of these conditions in the United States, where GMOs are ubiquitous in the food supply to the United Kingdom, where essentially no GMOs are consumed, there were no significant differences.

That said, it must be emphasized that science is ever changing, the science of genetic engineering is relatively young, and there is still uncertainty around long term effects. Absolute safety cannot be guaranteed for any specific food. However, companies do withdraw products from consideration that are determined to be unsafe. In 1996, researchers found that an allergen from Brazil nuts continued to be allergenic when transferred into a GMO soybean. That soybean was never approved. This experience resulted in policies that proteins that have ever been suspected of being or shown to be an allergen should never be introduced in GMO crops.

The FDA developed its Plant Biotechnology Consultation Program in the 1990’s to cooperatively work with GE (genetically engineered) plant developers to help make sure that foods made from their new GE plant varieties are safe and meet all regulations. FDA evaluates the safety of food produced by new GE crops before it enters the market. This is a voluntary program and FDA has evaluated 150 genetically engineered foods since the program began. These evaluations are publicly available on the FDA website, www.fda.gov .

By Diane Hirsch, Extension Educator Emerita, UConn Extension

Published October 18, 2017

September 1, 2013

13 min read

The Truth about Genetically Modified Food

Proponents of genetically modified crops say the technology is the only way to feed a warming, increasingly populous world. Critics say we tamper with nature at our peril. Who is right?

By David H. Freedman

Robert Goldberg sags into his desk chair and gestures at the air. “Frankenstein monsters, things crawling out of the lab,” he says. “This the most depressing thing I've ever dealt with.”

Goldberg, a plant molecular biologist at the University of California, Los Angeles, is not battling psychosis. He is expressing despair at the relentless need to confront what he sees as bogus fears over the health risks of genetically modified (GM) crops. Particularly frustrating to him, he says, is that this debate should have ended decades ago, when researchers produced a stream of exonerating evidence: “Today we're facing the same objections we faced 40 years ago.”

Across campus, David Williams, a cellular biologist who specializes in vision, has the opposite complaint. “A lot of naive science has been involved in pushing this technology,” he says. “Thirty years ago we didn't know that when you throw any gene into a different genome, the genome reacts to it. But now anyone in this field knows the genome is not a static environment. Inserted genes can be transformed by several different means, and it can happen generations later.” The result, he insists, could very well be potentially toxic plants slipping through testing.

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Williams concedes that he is among a tiny minority of biologists raising sharp questions about the safety of GM crops. But he says this is only because the field of plant molecular biology is protecting its interests. Funding, much of it from the companies that sell GM seeds, heavily favors researchers who are exploring ways to further the use of genetic modification in agriculture. He says that biologists who point out health or other risks associated with GM crops—who merely report or defend experimental findings that imply there may be risks—find themselves the focus of vicious attacks on their credibility, which leads scientists who see problems with GM foods to keep quiet.

Whether Williams is right or wrong, one thing is undeniable: despite overwhelming evidence that GM crops are safe to eat, the debate over their use continues to rage, and in some parts of the world, it is growing ever louder. Skeptics would argue that this contentiousness is a good thing—that we cannot be too cautious when tinkering with the genetic basis of the world's food supply. To researchers such as Goldberg, however, the persistence of fears about GM foods is nothing short of exasperating. “In spite of hundreds of millions of genetic experiments involving every type of organism on earth,” he says, “and people eating billions of meals without a problem, we've gone back to being ignorant.”

So who is right: advocates of GM or critics? When we look carefully at the evidence for both sides and weigh the risks and benefits, we find a surprisingly clear path out of this dilemma.

Benefits and worries

The bulk of the science on GM safety points in one direction. Take it from David Zilberman, a U.C. Berkeley agricultural and environmental economist and one of the few researchers considered credible by both agricultural chemical companies and their critics. He argues that the benefits of GM crops greatly outweigh the health risks, which so far remain theoretical. The use of GM crops “has lowered the price of food,” Zilberman says. “It has increased farmer safety by allowing them to use less pesticide. It has raised the output of corn, cotton and soy by 20 to 30 percent, allowing some people to survive who would not have without it. If it were more widely adopted around the world, the price [of food] would go lower, and fewer people would die of hunger.”

In the future, Zilberman says, those advantages will become all the more significant. The United Nations Food and Agriculture Organization estimates that the world will have to grow 70 percent more food by 2050 just to keep up with population growth. Climate change will make much of the world's arable land more difficult to farm. GM crops, Zilberman says, could produce higher yields, grow in dry and salty land, withstand high and low temperatures, and tolerate insects, disease and herbicides.

Credit: Jen Christiansen

Despite such promise, much of the world has been busy banning, restricting and otherwise shunning GM foods. Nearly all the corn and soybeans grown in the U.S. are genetically modified, but only two GM crops, Monsanto's MON810 maize and BASF's Amflora potato, are accepted in the European Union. Ten E.U. nations have banned MON810, and although BASF withdrew Amflora from the market in 2012, four E.U. nations have taken the trouble to ban that, too. Approval of a few new GM corn strains has been proposed there, but so far it has been repeatedly and soundly voted down. Throughout Asia, including in India and China, governments have yet to approve most GM crops, including an insect-resistant rice that produces higher yields with less pesticide. In Africa, where millions go hungry, several nations have refused to import GM foods in spite of their lower costs (the result of higher yields and a reduced need for water and pesticides). Kenya has banned them altogether amid widespread malnutrition. No country has definite plans to grow Golden Rice, a crop engineered to deliver more vitamin A than spinach (rice normally has no vitamin A), even though vitamin A deficiency causes more than one million deaths annually and half a million cases of irreversible blindness in the developing world.

Globally, only a tenth of the world's cropland includes GM plants. Four countries—the U.S., Canada, Brazil and Argentina—grow 90 percent of the planet's GM crops. Other Latin American countries are pushing away from the plants. And even in the U.S., voices decrying genetically modified foods are becoming louder. In 2016 the U.S. federal government passed a law requiring labeling of GM ingredients in food products, replacing GM-labeling laws in force or proposed in several dozen states.

The fear fueling all this activity has a long history. The public has been worried about the safety of GM foods since scientists at the University of Washington developed the first genetically modified tobacco plants in the 1970s. In the mid-1990s, when the first GM crops reached the market, Greenpeace, the Sierra Club, Ralph Nader, Prince Charles and a number of celebrity chefs took highly visible stands against them. Consumers in Europe became particularly alarmed: a survey conducted in 1997, for example, found that 69 percent of the Austrian public saw serious risks in GM foods, compared with only 14 percent of Americans.

In Europe, skepticism about GM foods has long been bundled with other concerns, such as a resentment of American agribusiness. Whatever it is based on, however, the European attitude reverberates across the world, influencing policy in countries where GM crops could have tremendous benefits. “In Africa, they don't care what us savages in America are doing,” Zilberman says. “They look to Europe and see countries there rejecting GM, so they don't use it.” Forces fighting genetic modification in Europe have rallied support for “the precautionary principle,” which holds that given the kind of catastrophe that would emerge from loosing a toxic, invasive GM crop on the world, GM efforts should be shut down until the technology is proved absolutely safe.

But as medical researchers know, nothing can really be “proved safe.” One can only fail to turn up significant risk after trying hard to find it—as is the case with GM crops.

A clean record

The human race has been selectively breeding crops, thus altering plants' genomes, for millennia. Ordinary wheat has long been strictly a human-engineered plant; it could not exist outside of farms, because its seeds do not scatter. For some 60 years scientists have been using “mutagenic” techniques to scramble the DNA of plants with radiation and chemicals, creating strains of wheat, rice, peanuts and pears that have become agricultural mainstays. The practice has inspired little objection from scientists or the public and has caused no known health problems.

The difference is that selective breeding or mutagenic techniques tend to result in large swaths of genes being swapped or altered. GM technology, in contrast, enables scientists to insert into a plant's genome a single gene (or a few of them) from another species of plant or even from a bacterium, virus or animal. Supporters argue that this precision makes the technology much less likely to produce surprises. Most plant molecular biologists also say that in the highly unlikely case that an unexpected health threat emerged from a new GM plant, scientists would quickly identify and eliminate it. “We know where the gene goes and can measure the activity of every single gene around it,” Goldberg says. “We can show exactly which changes occur and which don't.”

And although it might seem creepy to add virus DNA to a plant, doing so is, in fact, no big deal, proponents say. Viruses have been inserting their DNA into the genomes of crops, as well as humans and all other organisms, for millions of years. They often deliver the genes of other species while they are at it, which is why our own genome is loaded with genetic sequences that originated in viruses and nonhuman species. “When GM critics say that genes don't cross the species barrier in nature, that's just simple ignorance,” says Alan McHughen, a plant molecular geneticist at U.C. Riverside. Pea aphids contain fungi genes. Triticale is a century-plus-old hybrid of wheat and rye found in some flours and breakfast cereals. Wheat itself, for that matter, is a cross-species hybrid. “Mother Nature does it all the time, and so do conventional plant breeders,” McHughen says.

Could eating plants with altered genes allow new DNA to work its way into our own? It is possible but hugely improbable. Scientists have never found genetic material that could survive a trip through the human gut and make it into cells. Besides, we are routinely exposed to—and even consume—the viruses and bacteria whose genes end up in GM foods. The bacterium Bacillus thuringiensis , for example, which produces proteins fatal to insects, is sometimes enlisted as a natural pesticide in organic farming. “We've been eating this stuff for thousands of years,” Goldberg says.

In any case, proponents say, people have consumed as many as trillions of meals containing genetically modified ingredients over the past few decades. Not a single verified case of illness has ever been attributed to the genetic alterations. Mark Lynas, a prominent anti-GM activist who in 2013 publicly switched to strongly supporting the technology, has pointed out that every single news-making food disaster on record has been attributed to non-GM crops, such as the Escherichia coli –infected organic bean sprouts that killed 53 people in Europe in 2011.

Critics often disparage U.S. research on the safety of genetically modified foods, which is often funded or even conducted by GM companies, such as Monsanto. But much research on the subject comes from the European Commission, the administrative body of the E.U., which cannot be so easily dismissed as an industry tool. The European Commission has funded 130 research projects, carried out by more than 500 independent teams, on the safety of GM crops. None of those studies found any special risks from GM crops.

Plenty of other credible groups have arrived at the same conclusion. Gregory Jaffe, director of biotechnology at the Center for Science in the Public Interest, a science-based consumer-watchdog group in Washington, D.C., takes pains to note that the center has no official stance, pro or con, with regard to genetically modifying food plants. Yet Jaffe insists the scientific record is clear. “Current GM crops are safe to eat and can be grown safely in the environment,” he says. The American Association for the Advancement of Science, the American Medical Association and the National Academy of Sciences have all unreservedly backed GM crops. The U.S. Food and Drug Administration, along with its counterparts in several other countries, has repeatedly reviewed large bodies of research and concluded that GM crops pose no unique health threats. Dozens of review studies carried out by academic researchers have backed that view.

Opponents of genetically modified foods point to a handful of studies indicating possible safety problems. But reviewers have dismantled almost all of those reports. For example, a 1998 study by plant biochemist Árpád Pusztai, then at the Rowett Institute in Scotland, found that rats fed a GM potato suffered from stunted growth and immune system–related changes. But the potato was not intended for human consumption—it was, in fact, designed to be toxic for research purposes. The Rowett Institute later deemed the experiment so sloppy that it refuted the findings and charged Pusztai with misconduct.

Similar stories abound. Most recently, a team led by Gilles-Éric Séralini, a researcher at the University of Caen Lower Normandy in France, found that rats eating a common type of GM corn contracted cancer at an alarmingly high rate. But Séralini has long been an anti-GM campaigner, and critics charged that in his study, he relied on a strain of rat that too easily develops tumors, did not use enough rats, did not include proper control groups and failed to report many details of the experiment, including how the analysis was performed. After a review, the European Food Safety Authority dismissed the study's findings. Several other European agencies came to the same conclusion. “If GM corn were that toxic, someone would have noticed by now,” McHughen says. “Séralini has been refuted by everyone who has cared to comment.”

Some scientists say the objections to GM food stem from politics rather than science—that they are motivated by an objection to large multinational corporations having enormous influence over the food supply; invoking risks from genetic modification just provides a convenient way of whipping up the masses against industrial agriculture. “This has nothing to do with science,” Goldberg says. “It's about ideology.” Former anti-GM activist Lynas agrees. He has gone as far as labeling the anti-GM crowd “explicitly an antiscience movement.”

Persistent doubts

Not all objections to genetically modified foods are so easily dismissed, however. Long-term health effects can be subtle and nearly impossible to link to specific changes in the environment. Scientists have long believed that Alzheimer's disease and many cancers have environmental components, but few would argue we have identified all of them.

And opponents say that it is not true that the GM process is less likely to cause problems simply because fewer, more clearly identified genes are replaced. David Schubert, an Alzheimer's researcher who heads the Cellular Neurobiology Laboratory at the Salk Institute for Biological Studies in La Jolla, Calif., asserts that a single, well-characterized gene can still settle in the target plant's genome in many different ways. “It can go in forward, backward, at different locations, in multiple copies, and they all do different things,” he says. And as U.C.L.A.'s Williams notes, a genome often continues to change in the successive generations after the insertion, leaving it with a different arrangement than the one intended and initially tested. There is also the phenomenon of “insertional mutagenesis,” Williams adds, in which the insertion of a gene ends up quieting the activity of nearby genes.

True, the number of genes affected in a GM plant most likely will be far, far smaller than in conventional breeding techniques. Yet opponents maintain that because the wholesale swapping or alteration of entire packages of genes is a natural process that has been happening in plants for half a billion years, it tends to produce few scary surprises today. Changing a single gene, on the other hand, might turn out to be a more subversive action, with unexpected ripple effects, including the production of new proteins that might be toxins or allergens.

Opponents also point out that the kinds of alterations caused by the insertion of genes from other species might be more impactful, more complex or more subtle than those caused by the intraspecies gene swapping of conventional breeding. And just because there is no evidence to date that genetic material from an altered crop can make it into the genome of people who eat it does not mean such a transfer will never happen—or that it has not already happened and we have yet to spot it. These changes might be difficult to catch; their impact on the production of proteins might not even turn up in testing. “You'd certainly find out if the result is that the plant doesn't grow very well,” Williams says. “But will you find the change if it results in the production of proteins with long-term effects on the health of the people eating it?”

It is also true that many pro-GM scientists in the field are unduly harsh—even unscientific—in their treatment of critics. GM proponents sometimes lump every scientist who raises safety questions together with activists and discredited researchers. And even Séralini, the scientist behind the study that found high cancer rates for GM-fed rats, has his defenders. Most of them are nonscientists, or retired researchers from obscure institutions, or nonbiologist scientists, but the Salk Institute's Schubert also insists the study was unfairly dismissed. He says that as someone who runs drug-safety studies, he is well versed on what constitutes a good-quality animal toxicology study and that Séralini's makes the grade. He insists that the breed of rat in the study is commonly used in respected drug studies, typically in numbers no greater than in Séralini's study; that the methodology was standard; and that the details of the data analysis are irrelevant because the results were so striking.

Schubert joins Williams as one of a handful of biologists from respected institutions who are willing to sharply challenge the GM-foods-are-safe majority. Both charge that more scientists would speak up against genetic modification if doing so did not invariably lead to being excoriated in journals and the media. These attacks, they argue, are motivated by the fear that airing doubts could lead to less funding for the field. Says Williams: “Whether it's conscious or not, it's in their interest to promote this field, and they're not objective.”

Both scientists say that after publishing comments in respected journals questioning the safety of GM foods, they became the victims of coordinated attacks on their reputations. Schubert even charges that researchers who turn up results that might raise safety questions avoid publishing their findings out of fear of repercussions. “If it doesn't come out the right way,” he says, “you're going to get trashed.”

There is evidence to support that charge. In 2009 Nature detailed the backlash to a reasonably solid study published in the Proceedings of the National Academy of Sciences USA by researchers from Loyola University Chicago and the University of Notre Dame. The paper showed that GM corn seemed to be finding its way from farms into nearby streams and that it might pose a risk to some insects there because, according to the researchers' lab studies, caddis flies appeared to suffer on diets of pollen from GM corn. Many scientists immediately attacked the study, some of them suggesting the researchers were sloppy to the point of misconduct.

A way forward

There is a middle ground in this debate. Many moderate voices call for continuing the distribution of GM foods while maintaining or even stepping up safety testing on new GM crops. They advocate keeping a close eye on the health and environmental impact of existing ones. But they do not single out GM crops for special scrutiny, the Center for Science in the Public Interest's Jaffe notes: all crops could use more testing. “We should be doing a better job with food oversight altogether,” he says.

Even Schubert agrees. In spite of his concerns, he believes future GM crops can be introduced safely if testing is improved. “Ninety percent of the scientists I talk to assume that new GM plants are safety-tested the same way new drugs are by the FDA,” he says. “They absolutely aren't, and they absolutely should be.”

Stepped-up testing would pose a burden for GM researchers, and it could slow down the introduction of new crops. “Even under the current testing standards for GM crops, most conventionally bred crops wouldn't have made it to market,” McHughen says. “What's going to happen if we become even more strict?”

That is a fair question. But with governments and consumers increasingly coming down against GM crops altogether, additional testing may be the compromise that enables the human race to benefit from those crops' significant advantages.

David H. Freedman is a journalist who has been covering science, business and technology for more than 30 years.

• Open access
• Published: 13 January 2022

Evaluation of adverse effects/events of genetically modified food consumption: a systematic review of animal and human studies

• Chen Shen 1 ,
• Xiang-Chang Yin 2 ,
• Bo-Yang Jiao 3 ,
• Jing Li 4 ,
• Peng Jia 5 ,
• Xiao-Wen Zhang 1 ,
• Xue-Hao Cheng 6 ,
• Jian-Xin Ren 6 ,
• Hui-Di Lan 7 ,
• Wen-Bin Hou 1 ,
• Min Fang 1 ,
• Yu-Tong Fei 1 ,
• Nicola Robinson 1 , 8 &
• Jian-Ping Liu   ORCID: orcid.org/0000-0002-0320-061X 1 , 9  

Environmental Sciences Europe volume  34 , Article number:  8 ( 2022 ) Cite this article

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A systematic review of animal and human studies was conducted on genetically modified (GM) food consumption to assess its safety in terms of adverse effects/events to inform public concerns and future research.

Seven electronic databases were searched from January 1st 1983 till July 11th 2020 for in vivo, animal and human studies on the incidence of adverse effects/events of GM products consumption. Two authors independently identified eligible studies, assessed the study quality, and extracted data on the name of the periodical, author and affiliation, literature type, the theme of the study, publication year, funding, sample size, target population characteristics, type of the intervention/exposure, outcomes and outcome measures, and details of adverse effects/events. We used the Chi-square test to compare the adverse event reporting rates in articles funded by industry funding, government funding or unfunded articles.

One crossover trial in humans and 203 animal studies from 179 articles met the inclusion criteria. The study quality was all assessed as being unclear or having a high risk of bias. Minor illnesses were reported in the human trial. Among the 204 studies, 59.46% of adverse events (22 of 37) were serious adverse events from 16 animal studies (7.84%). No significant differences were found in the adverse event reporting rates either between industry and government funding ( χ 2  = 2.286, P  = 0.131), industry and non-industry funding ( χ 2  = 1.761, P  = 0.185) or funded and non-funded articles ( χ 2  = 0.491, P  = 0.483). We finally identified 21 GM food-related adverse events involving 7 GM events (NK603 × MON810 maize, GTS 40-3-2 soybean, NK603 maize, MON863 maize, MON810 maize, MON863 × MON810 × NK603 maize and GM Shanyou 63 rice), which had all been on regulatory approval in some countries/regions.

Serious adverse events of GM consumption include mortality, tumour or cancer, significant low fertility, decreased learning and reaction abilities, and some organ abnormalities. Further clinical trials and long-term cohort studies in human populations, especially on GM food-related adverse events and the corresponding GM events, are still warranted. It suggests the necessity of labelling GM food so that consumers can make their own choice.

Introduction

Genetic modification is defined as introducing transgene(s) with desired traits into the recipient organism’s genome by recombinant deoxyribonucleic acid (DNA) technology, and therefore it does not occur naturally [ 1 , 2 , 3 ]. Genetically modified (GM) crops are thought to address food security, sustainability and climate change solutions by improving crop yields, conserving biodiversity, providing a better environment in terms of the insect-resistant and herbicide-tolerant traits, reducing CO 2 emissions and helping alleviate poverty through uplifting the economic situation [ 4 ]. Insect-resistant and herbicide-tolerant traits were first introduced into four types of crop, canola, cotton, maize and soybeans, at the beginning of GM production [ 5 ]. At present, the mainstream characteristics of new crops still pursue higher-yielding, more nutritious, pest- and disease-resistant and climate-smart to meet future demand for a yield increase of major crops such as wheat, rice and corn, due to the growing population [ 6 ].

Since 1996, the first year of commercialization of GM crops, 70 countries had adopted GM crops until 2018, including 26 countries that cumulatively planted 2.5 billion hectares of GM crops and an additional 44 countries that imported GM crops. During the 27 years (1992 to 2018), 4349 approvals for 387 GM events from 27 GM crops were granted by 70 countries involving 2063 for food (when the direct consumers are mainly humans), 1461 for feed (the products only intended for animal consumption) use and 825 for environmental release or cultivation [ 4 , 7 ]. The major agricultural product exporting countries like the U.S.A., Brazil and Argentina show over 90% adoption of biotech crops [ 4 ]. For GM animal products, biotech salmon, considered to be the first genetically engineered animal for human consumption, was approved by the United States Department of Agriculture and Food & Drug Administration in 2015 [ 8 ]. In addition, it is illegal to grow major GM food crops in China while there are substantial investments in biotechnology research and GM maize, soybeans, and canola are allowed to import and eat [ 9 ].

Genetically modified food, however, is an example of the controversial relation between the inherent uncertainty of the scientific approach and the need of consumers to use products resulting from scientific developments thought to be safe [ 10 ]. Significant health risks have not been reported in peer-reviewed studies on GM food safety/security, which may cause some publication bias [ 11 ] but with a few exceptions, like the most famous “Monarch Butterfly controversy” [ 12 ], "Pusztai case" [ 13 ] and the "Séralini case" [ 14 ]. Unexpected effects of GM crops were reported in these studies, occupying an important place in the pages of scientific journals. Nevertheless, the above controversies severely impacted the public image, leading to full or partial bans in 38 countries including the European Union [ 15 ].

The complexity of risk evaluation is shown in these conflicting results, and concerns about the citizen-consumers have been raised against GM food [ 10 ]. Of most concern, aroused from the controversial events and some research results, is the potential of carcinogenesis, teratogenesis [ 16 ], lethal effects and adverse influences on fertility. GM agriculture is now widely discussed in both positive and negative frames and currently serves as a hotbed of debate in the public and policymakers. Although there are some reports and evidence from human and animal studies on the potential health effects of GM food/feed, the evidence is not conclusive and public concerns have not been resolved.

We aimed to conduct a systematic review of animal and human studies on GM food consumption to assess its safety in terms of adverse effects/events to inform public concerns and future research.

This study was a systematic review of previously published studies, conducted and reported in adherence with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [ 17 ] guideline.

Search strategy

China National Knowledge Infrastructure (CNKI), Wanfang, VIP Database, Chinese Biomedical Database (SinoMed), PubMed, the Cochrane Library and Embase databases were searched from January, 1st, 1983 till July, 11th, 2020, using a predefined search strategy (Additional file 1 : Appendix S1). Reference lists of retrieved articles were also searched.

Eligibility criteria

Based on the evidence pyramid proposed by the Medical Center of State University of New York in 2001, we determined the type of research we included in the study. For a comprehensive evaluation of the literature, all in vivo animal studies and human studies (cross-sectional studies, case reports, case series, case–control studies, case–crossover studies, cohort studies, controlled clinical trials, including randomized trials, quasi-randomized trials and non-randomized trials) in multiple languages were included. Animal studies in all fields were included, that is, they could be clinical, agricultural and animal husbandry, veterinary medicine, life sciences, etc. Field studies were excluded.

The study population in animal studies was applied with inclusion criteria based on the categorization approach that highlights the actual use of them: laboratory animals and economical animals (livestock and aquatilia) were included, with no prespecified limitations on age, population, species/races, health status or others. Interventions/exposures of the genetically modified animal/plant/microorganism products included for animal/human ingestion referred to GM food, GM food ingredients and GM feed, regardless of their dosage or duration. The GM strain (line) and GM event were not limited. There was no restriction on whether controls were or were not included. The studies were excluded if they focused on the effects of GM food/feed on secondary or multilevel consumers in the food chain where GM food/feed was only consumed by primary consumers in the predator relationships. For instance, if non-GM fishes were fed with diet containing GM ingredients and then the fish was fed to the experimental cats, the study was excluded.

Outcomes focused on the incidence of adverse effects or adverse events in GM food/feed consumption, including primary outcomes on carcinogenesis, teratogenesis, lethal effect (all-cause mortality) and reproduction and secondary outcomes on other biomarkers were included. Toxicity studies of general toxicity studies (acute, sub-acute, sub-chronic, chronic and carcinogenicity toxicity studies) and specific toxicity studies (genotoxicity, reproductive and developmental toxicity, immunotoxicity and other toxicology studies) were included. Mortality in pups before weaning was considered as an outcome of reproductive toxicity but not as a lethal effect. Outcomes of adverse events in laboratory testing would not be included only when they could indicate tissue or organ toxicity. Outcomes of adverse events in breeding performance in animal husbandry studies, which focused on the economic benefits of the animal products, were included and these indicators were regarded as reproduction biomarkers in this research.

Outcomes of adverse events on growth performance, carcass traits, meat and fur production performance and meat quality for economic benefit evaluation of live stocks were excluded, of which the indicators included final body weight, weight gain, feed to gain ratio, half-eviscerated weight, eviscerated weight, percentage of eviscerated yield and muscle lean meat, sebum rate in some parts of the body, etc. Studies on the insecticidal effect of insect-resistant GM feed and outcomes of adverse events in gene fragments residual in the digestive tract were excluded. Besides, duplicate publications, studies with duplicate statistics, or references devoid of necessary information of participants, sample size, interventions/exposures or results were excluded.

Study selection and data extraction

Titles and abstracts of the retrieved articles were reviewed by 6 researchers in pair (C Shen, XC Yin, BY Jiao, J Peng, YZ Li, XH Cheng). 6 authors (C Shen, XC Yin, BY Jiao, JX Ren, J Li and XW Zhang) independently reviewed the full texts to identify the studies meeting eligibility criteria and then 8 researchers in pair (C Shen, XC Yin, BY Jiao, J Li, P Jia, XW Zhang, XH Cheng and JX Ren) independently extracted data from the included studies according to a predesignated extraction table. The discrepancies were resolved through consensus and if necessary, arbitrated by another author (JP Liu).

We extracted the name of the periodical, author and affiliation, literature type, the theme of the study, publication year, funding, sample size, target population characteristics, type of the intervention/exposure, outcomes and outcome measures. For those studies in which adverse effects/events occurred, details of interventions/exposures and control conditions (if any), dosage, duration, number of the generation, and the results were extracted.

Quality assessment

The methodological quality for animal studies was assessed, using criteria from the SYRCLE’s risk of bias tool for animal studies. The quality of animal studies was categorized into low risk of bias, unclear risk of bias, or high risk of bias according to the risk for each important outcome within included studies, including the adequacy of generation of the sequence generation, baseline characteristics, allocation concealment, random housing, blinding (performance bias), random outcome assessment, blinding (detection bias), incomplete outcome data, selective outcome reporting, or other sources of bias. The judgment of other risk of bias was based on whether there were contamination (pooling drugs), inappropriate influence of funders, unit of analysis errors, design-specific risks of bias or new animals added to the control and experimental groups to replace drop-outs from the original population.

Statistical synthesis and analyses

Statistical analyses were carried out using Microsoft Excel 2016 and SPSS 20.0. The findings were reported mainly in two parts, characteristics of the included studies and detailed information on the studies in which adverse effects/events occurred. Initially, descriptive statistics, frequencies, and percentages were calculated to summarize the data. Subsequently, studies that evaluated similar populations, interventions, controls (if any) and outcomes were pooled using a random-effects meta-analysis, and data from other studies were presented in tables and described in a narrative summary. The incidence of adverse events reported in articles funded by industry funding, government funding or unfunded articles were, respectively, counted and the Chi-square test was used for the comparisons.

Besides, we figured the incidence of serious adverse events (SAEs) by percentage. With reference to the Food and Drug Administration’s definition [ 18 ], our study defined SAEs as death, life-threatening, hospitalization (initial or prolonged), disability or permanent change, disruption, impairment or damage in a body function or structure (including cancer or tumour), in physical activities or quality of life, congenital anomaly or birth defect in the newborn child or pups, infertility or significant low in the number of deliveries or live birth rate than the non-GM commercial, conventional or blank controls, and an event resulting in intervention/treatment to prevent permanent impairment, damage or to prevent one of the other outcomes.

Meanwhile, the adverse events which cannot be ruled out that it has nothing to do with GM food (hereinafter abbreviated as GM food-related adverse events) were identified and the percentages under each outcome were calculated.

Description of studies

The flow diagram of the literature selection is shown in Fig.  1 . A total of 9668 records were identified, including 9584 from the initial search through seven databases and 84 from other sources. After removal of duplicates and exclusion of references by reading titles and abstracts, 455 full-text articles were screened and 276 references were excluded with reasons (seen in the flow chart). Finally, 204 studies from 179 articles [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 , 166 , 167 , 168 , 169 , 170 , 171 , 172 , 173 , 174 , 175 , 176 , 177 , 178 , 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 , 195 , 196 , 197 ] (153 journal articles, 22 dissertations, 3 conference proceedings and 1 unpublished report) were included in data synthesis, since there were more than one study conducted in each of the 2 included dissertations [ 107 , 127 ], 11 journal articles [ 19 , 33 , 35 , 63 , 67 , 88 , 102 , 118 , 132 , 172 , 184 ] and 1 unpublished report [ 32 ]. The included studies were of 203 in vivo animal studies and 1 crossover trial [ 97 ] in humans.

The flow of literature search and selection of studies on the safety of GM food

Study characteristics

Of the 179 included articles, 94 were in English [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 ], 83 were published in Chinese [ 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 , 166 , 167 , 168 , 169 , 170 , 171 , 172 , 173 , 174 , 175 , 176 , 177 , 178 , 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 , 195 ], and 2 in Japanese [ 196 , 197 ]. The earliest included reference dated back to 1998 [ 153 ] (shown in Fig.  2 ), after which the remaining articles were distributed from 2000 to 2020 (45 articles in the 2000s, while 131 in the 2010s and 2 in the 2020s). The year 2012 witnessed the largest volume of publication (n = 26 articles, 14.53%). For funding sources or sponsors (Additional file 1 : Appendix S2), in addition to 57 articles not mentioning the funding/sponsor (hereinafter as non-funded articles), there were 116 articles (64.8% of the 179 articles) supported by 56 kinds of government funding from 12 countries/government organizations and, still, 9 articles (5.03%) by 10 kinds of industry/institute funding sources/sponsors from 4 countries (America, Australia, French and German). Among them, 3 articles [ 29 , 62 , 74 ] claimed to have been funded or sponsored by both government and industry. China had undertaken the most government/school-level funding projects (39 of 56 projects, 69.64%).

The publications (number of articles) on the safety of GM food by year

The periodicals that have published more than 5 included articles were Food and Chemical Toxicology (published 25 included articles), EFSA Journal (13), Regulatory Toxicology and Pharmacology (9), Journal of Hygiene Research (9) and Chinese Journal of Food Hygiene (8). 11 of 13 authors, who have published ten or more included studies, were from European Food Safety Authority and published 12 included articles as co-authors. They were Christina Tlustos (published 12 included articles), Claudia Bolognesi (12), Konrad Grob (12), Vittorio Silano (12), Andre Penninks (11), Gilles Riviere (11), Holger Zorn (11), Karl-Heinz Engel (11), Yi Liu (11), Natalia Kovalkovicova (10), Sirpa Karenlampi (10). In addition to the above 12 articles, the top 3 of the 11 authors who published five or more included studies was Yang Xiao-Guang (from Chinese Center for Disease Control and Prevention, published 11 included articles), Wang Jing (from Tianjin Centre for Disease Control and Prevention, published 10 included articles) and Zhuo Qin (from Chinese Center for Disease Control and Prevention, published 7 included articles). The top 5 affiliations which published included articles were Chinese Center for Disease Control and Prevention (published 16 included articles), Tianjin Centre for Disease Control and Prevention (12), European Food Safety Authority (12), National Chung Hsing University (10), International Rice Research Institute (9).

Of the 204 included studies, one was a double-blind crossover trial ( n  = 36) in humans and the others were all animal studies. Individual sample sizes of the total 54,392 study population ranged from 4 (cats) [ 153 ] to 21,000 (Atlantic salmon) [ 23 ]. The studies involved 14 different kinds of animals (see Table 1 ). Apart from the most commonly used rats/mice (in 160 studies, 78.82%), pigs and chicks were two of the most extensively studied animals (in 23 studies, 11.33%). For themes of the 178 included animal studies, 158 were on clinical and 20 were on agricultural and animal husbandry. For the ones on clinical, 117 were on general toxicity (8 on acute, 6 sub-acute, 84 sub-chronic, 16 chronic toxicity, and still 3 on both acute, sub-acute and sub-chronic toxicity), 35 on specific toxicity (15 on reproductive and developmental toxicity, 16 on immunotoxicity, 3 on teratogenic effect and 1 on mutagenicity), 3 on allergenicity, 1 on learning and memory ability, 1 on athletic ability and 1 on both sub-chronic toxicity and allergenicity.

For interventions/exposures, 31 kinds of GM food were identified, including 18 kinds of GM plant food, 7 kinds of GM animal food and 6 kinds of GM microorganism food. Each included study covered one intervention/exposure, except for one study, Chen [ 29 ], that involved two kinds of GM products (sweet pepper and tomato) modified with the same gene (coat protein gene of cucumber mosaic virus), respectively, in two experimental groups. Maize, rice and soybean were the three most popular kinds of GM plant food (taken 79.38%) in research while milk/milk powder and animal-derived protein occupied the top two in GM animal food (56.25%). As for GM microorganism products, 5 kinds of food/feed enzyme derived from 5 different kinds of GM fungi or bacteria as well as 1 kind of microorganism-derived protein were among included studies.

Methodological quality of the animal studies

According to our predefined quality assessment criteria, all of the studies were identified as being unclear or having a high risk of bias (Fig.  3 ). None of the studies were reported to blind researchers from knowing which intervention each animal received. None of the studies reported prior sample-size calculation, 31 studies (15.27%) described wrong randomization procedures or did not mention the method of “randomization”, and 12 studies (5.91%) did not report adequate allocation concealment. 28 studies (13.79%) described that the groups were similar at baseline and 76 studies (37.44%) claimed that the housing conditions of animals from the various experimental groups were identical. 10 studies (4.93%) described randomly pick an animal during outcome assessment while 7 studies (3.45%) failed to select animals at random for outcome assessment. 88 studies (43.35%) completely used objective outcome indicators for outcome measurement. 185 studies (91.13%) reported consistent outcomes in the method and result sections while 5 studies did not, but none of the study protocols were available.

Risk of bias of the included animal studies

Incidence of adverse events/effects

No meta-analysis was conducted due to the significant heterogeneity of the primary studies. Among the 204 studies, a total of 29 studies (14.22%) from 23 articles reported 37 adverse events, involving 13 on mortality, 6 on reproductive toxicity, 3 on carcinogenesis and 15 on other biomarkers (including one human trial). It is worth noting that when, in one study, there were multiple aspects of adverse events on “other biomarkers”, we recorded it as 1 adverse event. Then, 22 serious adverse events (59.46% of adverse events) were identified in 16 studies (7.84% of the included studies and 55.17% of the studies reporting adverse events, marked in the tables with double asterisks). The SAEs mainly rested on mortality (13 studies), tumour or cancer (3), significant low in the number of pup deliveries (2), decreased learning and reaction abilities (1), severe stomach inflammation (1), intestinal adenoma lesions (1), and other pathology abnormalities (1) as hypertrophies and hyperplasia in mammary glands and pituitary, liver congestions and necrosis as well as severe chronic progressive nephropathies.

The incidence of adverse events reporting in government funding, industry funding and non-funded articles were 10.34% (12 of 116), 33.33% (3 of 9) and 15.79% (9 of 57), respectively. When comparing the adverse event reporting rates using the Chi-square test, we found that there were no significant differences either between industry funding and government funding ( χ 2  = 2.286, P  = 0.131), industry funding and non-industry funding ( χ 2  = 1.761, P  = 0.185) or funded and non-funded articles ( χ 2  = 0.491, P  = 0.483).

Incidence of adverse events/effects in human trial

As for the human trial [ 97 ], shown in Table 2 , a randomized double-blind crossover design was conducted for acute consumption of two single breakfasts, with a 14-day washout period, containing either seed oil generated from transgenic Camelina sativa plants or commercially blended fish oil. 36 healthy people were randomly allocated into two groups and venous blood samples were collected after the postprandial session, 8 h after each meal. No follow-up was reported. No major adverse symptoms or health effects were reported but some unrelated minor illnesses for the 72 postprandial sessions from 36 participants, such as minor upper respiratory tract infections (2.78%), minor nose bleed (1.39%), pyelonephritis (1.39%) and headaches (8.33%).

Incidence of adverse events/effects in animal studies

For the 203 animal studies, 28 studies (13.79%) from 22 articles reported 36 adverse events, including 13 on mortality (Table 3 , 36.11%), 6 on reproductive toxicity ( Table 4 , 16.67%), 3 on carcinogenesis (Table 5 , 8.33%) and 14 on other biomarkers (Additional file 1 : Appendix S3, 38.89%).

All causes of death were included in this analysis and 11 of the 13 studies claimed that the mortality was not significantly different between the groups or had nothing to do with GM food. One study (Ermakova [ 37 ]) reported higher pup mortality in the Roundup-Ready soya (40.3.2 line) group compared with the controls. In Séralini [ 74 ] , the general cause of death was large mammary tumours in females and other organ problems in males. Besides, rats in the Roundup-tolerant GM NK603 maize groups were 2–3 times more likely to die than controls, and more rapidly.

With respect to effects on reproduction, 5 animal feeding studies were reported to trigger reproductive toxicity but one study (Cisterna [ 31 ]) claimed to have no substantial impact on fertility. The reproductive toxicity manifested in the significant low in the number of deliveries, survival rate (from birth to weaning), litter weight, litter size and weight of some organs in the pups. For example, in Ermakova I 2005, the rats fed with Roundup-Ready soya had a 55.6% pup mortality rate during lactation periods compared to 9% in the control of traditional soya and 6.8% in the reference group. The pups kept dying during the lactation period while pups from the control group only died during the first week. Cyran N 2008 a and Cyran N 2008 c [ 32 ] were two rat feeding studies reported in one article, both given NK603 × MON810 maize. A multi-generation study was conducted as Cyran N 2008 a while Cyran N 2008 c did a continuous breeding study. Both of them indicated that fewer sum of pups was born and weaned in the GM groups. Pup losses, in Cyran N 2008 a, overall generations were about twice as many pups lost as compared to the control group (14.59% vs 7.4%) but was not significantly different and significantly lower litter weight was also reported in Cyran N 2008 c.

Three mouse/rat feeding studies reported triggering cancers/tumours when Tang [ 156 ] attributed the incidence of the tumour to the elder age of rats. Séralini 2014 (on Roundup-tolerant GM maize) found that females in the treatment groups almost always developed large mammary tumours more often than and controls. As for males, 4 times larger palpable tumours than controls were presented which emerged up to 600 days earlier. Cyran 2008 b [ 32 ] revealed a life term study where mice in the three groups were fed with transgenic maize NK603xMON810 (from 33.0% in the diet), control isoline diet and GM-free Austrian corn reference diet, respectively. The survival rate was not significantly different while cancer (leucosis) was the common cause of death.

GM food-related adverse events

Among the 37 adverse events reported, 16 of them claimed to have nothing to do with GM food, while the rest 21 (from 17 studies) did not, still leaving the question open. The GM food-related adverse events existed in mortality (2 studies), reproductive toxicity (5), carcinogenesis (2), and other biomarkers (12).

By gathering evidence, we identified 3 kinds of GM food associated with adverse events, GM soybean, GM maize as well as GM rice. For the 17 studies involved in the GM food-related adverse events, 4 studies were absent of information on the GM event of their test substance and the remainder concentrated on 7 GM events (3 studies on NK603 × MON810 maize, 2 on GTS 40-3-2 soybean, 2 on NK603 maize, 2 on MON863 maize, 2 on MON810 maize, 1 on maize mixed with MON863 × MON810 × NK603, NK603 × MON810 and NK603 and 1 on GM Shanyou 63 rice). When searching in the GM Approval Database on the ISAAA website, we found that all of the first 6 GM events listed, all developed by Monsanto Company, had been on regulatory approval for food, feed and cultivation in multiple countries/regions, including the European Union. GM -39 Shanyou 63 was developed in China and given approval for food, feed, and cultivation only by China in 2009.

Summary of findings

We included 203 in vivo animal studies and 1 human trial, and all of the studies were identified as being unclear or having a high risk of bias. Overall, we reported two main findings. First, we identified 37 adverse events for GM food consumption while 22 of them (59.46%) were serious adverse events extracted from 16 animal studies (7.84%). SAEs were mortality, tumour or cancer, significantly low in the number of pup deliveries, decreased learning and reaction abilities, severe stomach inflammation, intestinal adenoma lesions, and other pathological abnormalities in the mammary glands, pituitary, liver and kidney.

Second, there were 21 GM food-related adverse events indicating that GM food may have effects on increased mortality (2 studies), reproductive toxicity (5 studies), which referred to significantly low fertility in parental generation and low survival rate, litter weight, litter size and weight of some organs in the pups, carcinogenesis (2 studies) and other biomarkers (12 studies). The effect-related GM food included 7 GM events (NK603 × MON810 maize, GTS 40-3-2 soybean, NK603 maize, MON863 maize, MON810 maize, MON863 × MON810 × NK603 maize and GM Shanyou 63 rice), which had all been on regulatory approval for food, feed and cultivation in some countries/regions.

Agreements and disagreements with other reviews

To our knowledge, there have been 3 previous systematic reviews (SRs) [ 198 , 199 , 200 ] and 6 conventional reviews [ 16 , 201 , 202 , 203 , 204 , 205 ] addressing similar research questions on the unexpected effects of GM food consumption. Keshani et al. [ 198 ], searching in 4 English databases, included experimental studies on GM crops’ potential effects on sperm parameters. The study finally included 7 rat feeding studies, which were all identified in our study, and indicated no harm to GM plants consumers. Edge et al. [ 199 ] addressed 30 review questions for including human studies, published in recent 20 years (1994–2014), on health effects of genetically engineered (GE) food crops, but found no human study on 25 questions. The remaining 5 questions, related to allergenicity and nutrient adequacy, were answered based on 21 human studies. The human studies were all excluded in our research because of no direct ingestion of GE food in the allergenicity assessment studies or no targeted outcomes in the nutrient assessment trial. To illustrate, the above-mentioned nutrient assessment clinical trial evaluated the effect of carrots containing twofold higher calcium content on calcium absorption and we thought it was not on outcome related to adverse events/effects. The conclusion of the research also supported that there were no clear adverse health effects associated with the consumption of GE food. Moreover, Dunn et al. [ 200 ] included both human and animal studies for examining the allergenicity of GM organisms and finally found 34 human studies and 49 animal studies eligible. In addition to 32 human studies which involved human serum for IgE binding or inhibition studies and not direct consumption of GM product, the rest 2 [ 206 , 207 ]studies were on actual ingestion of a GM food. However, they were not included in our research because of not targeted study type and unrelated outcomes. The conclusion agreed with the first two SRs that GM foods did not appear to be more allergenic than their conventional counterparts.

As for conventional reviews, Domingo showed special attention to the safety of GM food and published four literature reviews in 2000 [ 203 ], 2007 [ 204 ], 2011 [ 205 ] and 2016 [ 16 ]. Domingo searched two databases, PubMed and Scopus, to assess adverse/toxic effects of GM plants. In the latest updated review, he addressed the conclusion that GM soybeans, rice, corn/maize and wheat would be as safe as the parental species of these plants. However, our results may not be consistent with Domingo’s conclusion: we focus on a summarization of adverse events for GM food consumption through a systematic search in 7 databases; we identified 37 adverse events, 22 serious adverse events and 21 GM food-related adverse events; GM maize, soybean and rice with some specific GM events were all related to GM food-related adverse events. In addition, Domingo found a notable advance of studies published in scientific journals by biotechnology companies. Coincidentally, we did a Chi-square test to compare the adverse event reporting rates and found no significant differences between industry funding, government funding and non-funded articles. Besides, our systematic review validated Domingo’s findings that some GM plants were studied scarcely in recent years including GM potatoes discussed in the controversy of Pusztai case.

Strengths and limitations

In this review, a systematic search of major databases was conducted to identify all available studies in all languages on the adverse effects/events of GM food consumption. To make the inclusion and data synthesis comprehensive, both in vivo human and animal studies in all fields were included, with no limitations on the type of participant, type of intervention/exposure or whether control was included. The terms used for searching, containing all kinds of names of GM food, were based on a basic search on the internet by the researchers and the list was perfected as much as possible. With respect to additional searching, we went through multifarious news which reported controversy of GM food and thus we identified several hot studies by following the clue. In order to trace the potential conflicts of interest, we performed a Chi-square test for comparing adverse events report rates in articles funded by industry funding, government funding or unfunded articles, but found no statistical significance. Nevertheless, it was hard to conduct a quantitative data synthesis for the effects of GM food consumption on the adverse events because of the significant heterogeneity of the primary studies.

There are several limitations in this review. The methodological quality of the included studies is generally poor, which indicates a high or unclear risk of bias resulting from insufficient reporting of methodological components in the studies. Methodological quality may not be fully reflected based solely on the reporting of the manuscript. There were unclear descriptions of randomization procedures and a lack of blinding in all of the studies, which may have created potential performance biases and detection biases, as researchers might have been aware of the effects of interventions. The ability to perform meta-analysis was limited because of the heterogeneity of the participants, interventions (GM food in various GM events), comparisons, feeding doses, administration time, other exposure factors, and the variance of composite outcome measures used in the 204 included studies. When we did the manual search, we found that related publications were retracted sometimes, under the name of inadequate experimental designs or statistical analysis. For example, Séralini 2012 was retracted by Food and Chemical Toxicology , but subsequently republished in another journal [ 14 , 74 ]. This indicates that it was hard for us to find the original full-text papers of the retracted publications and articles provided by databases still have some unavoidable publication bias. The retraction on controversial researches may also cause the controversy for the public to doubt the reality of the studies published and to concern the safety of GM food. In addition, the lack of human studies is another key limitation of this research. As for the searching strategy, we did not include publication types as newspaper articles and comments. This was thought to be a limitation of this research because these sources may give us clues of related researches and can help us to do a manual search comprehensively. It is also an implication for future systematic reviews.

Implications for research

Future research should be conducted in humans, especially observational cohort studies. High-quality animal studies according to the ARRIVE reporting standard focusing on reproductive toxicity and carcinogenesis are still needed. Trials or studies should be registered prospectively, and be accessible. Furthermore, to address public concerns, future studies should focus on SAEs and GM food-related adverse events reported in this research such as NK603 maize, MON863 maize and MON810 maize. Meanwhile, some implications of findings still could be explored such as how GM food affects people’s eating habits, labelling of GM food and public choice. Some of the included studies conducted an intergenerational or multigenerational evaluation of the safety of GM food, but only two studies (Cyran N 2008 a and Cyran N 2008 c) in one article reported adverse events related to fertility. The differences in the results may be due to different interventions/exposures (GM food in certain GM events), laboratory animals, intervention/exposure time, experiment environment, etc. Therefore, it is necessary for subsequent studies to start with intergenerational or multigenerational research to verify the safety of GM food in terms of study design.

Serious adverse events accounted for 59.46% of the total 37 identified adverse events of GM consumption, which include: mortality, tumour or cancer, significantly lower number of pup deliveries, decreased learning and reaction abilities, and organ abnormalities in the stomach, intestinal adenoma, mammary glands, pituitary, liver and kidney. The interventions/exposures in the adverse event related studies emphasized on GM soybean, maize and rice in specific GM events. Animal studies occupy the lowest hierarchy of evidence, and there are flaws in study design and is not convincing enough. The evidence on the effect of GM consumption on humans is still insufficient. Further clinical trials and long-term cohort studies in human populations, especially on GM food-related adverse events and the corresponding GM events, are still warranted. It is better to prove the safety before they are approved for food consumption and it also suggests the necessity of labelling on GM food so that consumers can make their own choice.

Availability of data and materials

All data generated or analysed during this study are included in this published article.

Abbreviations

Genetically modified

Deoxyribonucleic acid

China National Knowledge Infrastructure

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Serious adverse event

Camelina sativa Seed oil

Blended fish oil

Body weight

Systematic reviews

Genetically engineered

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We appreciate Yi-Zhen Li for participating in screening the titles and abstracts .

This work was supported by Innovation Team and Talents Cultivation Program of National Administration of Traditional Chinese Medicine (ZYYCXTD-C-202006). Prof. Nicola Robinson (visiting professor of Beijing University of Chinese Medicine) was funded by the International development and capacity enhancement of evidence-based Chinese medicine Project, Ministry of Science and Technology of the People's Republic of China, G20200001187.

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Additional file 1: appendix s1..

Search strategy applied in English language databases. Appendix S2. Funding sources or sponsors. Appendix S3. Adverse events/effects—other biomarkers.

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Shen, C., Yin, XC., Jiao, BY. et al. Evaluation of adverse effects/events of genetically modified food consumption: a systematic review of animal and human studies. Environ Sci Eur 34 , 8 (2022). https://doi.org/10.1186/s12302-021-00578-9

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About half of U.S. adults are wary of health effects of genetically modified foods, but many also see advantages

Americans have mixed views about genetically modified foods (GMOs) and their implications for society. About half of U.S. adults (51%) think GMOs are worse for people’s health than foods with no genetically modified ingredients, while 41% say GM foods have a neutral effect on health. Just 7% say they are better for health than other foods.

Views about the health effects of such foods grew more negative between 2016 and 2018 and have been steady since then, according to Pew Research Center surveys, the latest of which was conducted in October 2019.

As Americans think about the effects of GMOs, about three-quarters (74%) say it is at least fairly likely that GM foods will increase the global food supply. And 62% say GM foods are very or fairly likely to lead to more affordably priced food.

How we did this

Pew Research Center has been tracking the American public’s attitudes about genetically modified foods as part of its continuing research on public views on scientific and technological developments. These findings are based on a survey conducted Oct. 1-13, 2019, among 3,627 U.S. adults.

Everyone who took part is a member of Pew Research Center’s American Trends Panel, an online survey panel that is recruited through national, random sampling of residential addresses. Recruiting our panelists by phone or mail ensures that nearly all U.S. adults have a chance of selection. This gives us confidence that any sample can represent the whole population (see our  Methods 101 explainer  on random sampling). To further ensure that each survey reflects a balanced cross section of the nation, the data is weighted to match the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories.

Indeed, many of those who consider genetically modified foods worse for health than conventionally grown foods see both positive and negative effects ahead for society. A strong majority of this group thinks GM foods are at least fairly likely to result in health problems for the population as a whole (88%) or create problems for the environment (77%). At the same time, half or more also say that such foods are at least fairly likely to help increase the global food supply (64%) or result in more affordably priced food (50%).

Those who believe that genetically modified foods are neither better nor worse for health than conventionally grown foods tend to expect positive benefits from GM foods for the global food supply (78% say an increase is very or fairly likely). But only about three-in-ten of this group thinks GM foods are at least fairly likely to result in health problems for the population as a whole (27%) or problems for the environment (30%). The 7% of U.S. adults who say that GM foods are better for health than other foods make up too small a sample for separate analysis.

Women are more inclined than men to believe that GM foods are worse for health (58% vs. 42%). Similarly, women are more likely to think GMOs are at least fairly likely to result in health problems for the population as a whole or to create problems for the environment.

Roughly three-in-ten U.S. adults (29%) report that they have heard a lot about foods with genetically modified ingredients, while 59% have heard a little and 12% say they have heard nothing at all about these foods. People who are more familiar with genetically modified foods are more likely to be concerned about their health effects: 55% of those who know a lot and a similar share (51%) of those who know a little about GM foods believe such foods are worse for health, compared with 39% of those who say they know nothing about GM foods.

Note: Here are the questions used for this report, along with responses, and its methodology.

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The human health benefits from GM crops

Stuart j. smyth.

1 Department of Agricultural and Resource Economics, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon Saskatchewan, Canada

Genetically modified (GM) crops represent the most rapidly adopted technology in the history of agriculture, having now reached 25 years of commercial production. Grown by millions of farmers, many in developing countries, the technology is providing significant economic and environmental benefits, such as reductions in chemical use of 37%, increased yields of 22% and improved farm profits of 68% (Klümper and Qaim, 2014 ). While knowledge and awareness of these benefits are increasingly communicated, less well known are the benefits that GM crops are providing to humans and human health.

From an adoption percentage, countries with highly industrialized, large‐scale agricultural production are the significant benefactors. Production in Argentina, Australia, Brazil, Canada and the USA accounts for the majority of global GM crop acreage, with farmers in these five countries capturing the majority of the economic and environmental benefits. Conversely, because of the lack of mechanized agricultural production, it is the small landholder farmers in developing countries that accrue the majority of the human health benefits.

Reductions in pesticide poisonings

While the application of agricultural chemicals is highly mechanized in industrial countries, the same cannot be said for developing countries, where most applications are done through human labour using handheld applicators. With average farm sizes commonly <10 acres in many developing countries, field sizes are even smaller, resulting in much, if not all, of the fieldwork (seeding, weeding, spraying and harvesting), being done by hand. Chemical applications, especially insecticides on crops such as cotton and brinjal, require numerous applications throughout the course of the growing season to ensure insect damage is as minimal as possible. This is crucial with brinjal production as visual evidence of insect damage prevents the sale of products for public consumption, resulting in significant income losses. The application of insecticides must be done as the plants grow and mature, through the use of backpack sprayers, resulting in skin absorption of chemical residues. Exposures to chemicals such as this result in sickness of the person applying the chemicals, known as pesticide poisoning. GM crops, particularly Bt cotton, have resulted in significant reductions in pesticide poisoning cases due to reduced applications and reduced levels of insecticide exposure.

Reductions in farmer pesticide poisonings have been quantified in China, India, Pakistan and South Africa. Often, cases of pesticide poisoning are not formally reported to health centres and the results on pesticide poisoning may be underestimated due to the lack of reporting. In South Africa, farmers reduced pesticide applications from 11.2 per year to 3.8, with reported cases of pesticide poisoning declining from over 50 per year to <10 over the first 4 years of Bt cotton adoption (Bennet et al ., 2003 ). One third of non‐Bt cotton farmers in China reported cases of pesticide poisoning, compared with 9% of Bt cotton‐producing farmers (Hossain et al ., 2004 ). Assessing the health impacts in India reveals a reduction in cases of pesticide poisoning of 2.4–9 million cases per year (Kouser and Qaim, 2011 ). Cumulatively, since 2003, when Bt cotton was first commercialized in India, a minimum of 38 million fewer instances of pesticide poisoning have occurred, with an upper potential of 144 million. Farmers in Pakistan growing non‐Bt cotton reported up to seven instances of pesticide poisoning in the growing season with 35% reporting no instances, versus Bt cotton farmers reporting up to six poisonings with 45% reporting none (Kouser and Qaim, 2013 ).

A medical assessment of 246 Chinese farmers, involving 35 health indicators, found that fungicides associated with the production of non‐Bt cotton had linkages to damaged liver function, while the insecticides used in non‐Bt cotton production may be associated with severe nerve damage (Zhang et al ., 2016 ). The use of non‐glyphosate tolerant crops was found to likely reduce renal function and decrease serum folic acid.

Changes in farmer suicide

Mental health challenges and issues affect all walks of life and economic sectors, with agriculture being no different. Access to sufficient mental health resources can be problematic within the agriculture sector due to rural areas, remote locations and lack of access to mental health support systems. Unfortunately, suicide is a concern in agriculture. India has one of the highest suicide rates in the world, and research has examined the relationship between farmer suicide and the adoption of GM cotton.

Research examining the relationship between farm suicide and Bt cotton adoption revealed a plateauing of the suicide rate following the commercialization of Bt cotton (Gruère and Sengupta, 2011 ). Farmer suicides were trending upward from 15 000 per year, peaking in 2004, the year after Bt cotton was first commercialized in India. By 2007, the actual suicide rate was 25% below the extrapolated suicide rate. Cumulatively, the reduced rate of suicide associated with the adoption of Bt cotton represents the prevention of a minimum of 75 000 farmer suicides.

Lowering cancer incidences

The development of insect‐resistant crop varieties has begun to have a noticeable potential to improve human health through the reduction in cancer rates. Prior to the commercialization of Bt crops, maize in particular, insect damage to the harvested crop increased the potential for the development of harmful health effects. A study of 21 years of maize production quantified that Bt maize contained lower concentrations of mycotoxins (29%), fumonisins (31%) and thricotecens (37%) (Pellegrino et al ., 2018 ). Mycotoxins are both toxic and carcinogenic to humans and animals and are considerably more concerning in developing economy food systems where access to food safety toxicity tests is less prevalent. Fumonisins are correlated to being the cause of higher rates of neural tube defects in high maize‐based diets (Missmer et al ., 2006 ). With food security challenges existing in many developing countries, corn containing mycotoxins are consumed as part of the household diet due to the lack of any other option.

Mental health benefits

One factor not assessed to date is the mental health improvements incurred by GM crop adopters. Stress in agriculture is like every other sector of the business economy, although in the agriculture sector, the stresses may be more related to financial debt servicing and the potentials of crop failure. Both of these factors can contribute to the stress burden of farmers. With the quantified higher yields from GM crops (Klümper and Qaim, 2014 ), farmers can now gain some degree of confidence that their crop will not fail due to insect pressures, be overcome with weeds and be more resilient should a drought occur.

Nutritional benefits

Genetically modified crops have made significant contributions to address the United Nations Sustainable Development Goals, in particular goals 1 (reducing poverty) and 2 (reducing hunger). While increased yields have contributed to higher household incomes, which reduce poverty, the increased yields have also enhanced household food security. Biofortified GM crops have been adopted, increasing micronutrient availability (Hefferon, 2014 ). Nutritionally enhanced foods improve an individual's nutrient intake, preventing and/or treating leading causes of death such as cancer, diabetes, cardiovascular disease and hypertension. Improving the nutritional content of daily food consumption certainly has day‐to‐day effects, but of significant importance are the long‐term effects that extend for decades over the course of an individual's lifetime.

In many instances, improving macronutrients (proteins, carbohydrates, lipids, fibre) and micronutrients (vitamins, minerals, functional metabolites) has significant childhood health improvements, such as reducing blindness due to the lack of vitamin availability. Improved food nutrient content, especially the increase in mineral availability, contributes to improved immunity systems and reduces stunting. In many developing countries, plant‐based nutrient intake accounts for one hundred per cent of an individual's nutrient diet, further highlighting the importance of nutritionally enhanced crop‐derived foods. As the later in life benefits from improved childhood nutrition are better understood, the full value of nutritionally enhanced GM crops and foods may not be realized for several decades.

Concluding remarks

While millions of farmers growing Bt cotton are experiencing reduced incidences of pesticide poisoning, all of the estimated 17 million farmers growing GM crops globally have reduced chemical exposures. Certainly, the reduced rates of pesticide poisoning, possibly in excess of 100 million cases, are a vital statistic of the benefits of GM crops, but perhaps the most significant is the contribution to improved mental health from farmers, especially those in India. Suicide is a devastating part of agriculture, to which no country is immune and the observed plateauing and now reduction in Indian farmer suicide rates is a benefit that simply cannot be surpassed. By allowing cotton farmers to be more profitable, Bt cotton has allowed tens of thousands of Indian cotton farmers to have more options and opportunities to continue farming. The true benefit of GM crops can be measured through the thousands of family members who no longer have to deal with the anguish and grief suicide causes.

Ongoing mental health improvements from the reduced stress of the potential for crop failure and the damaging effects this has on profitability and food security, while significantly difficult to measure, will continue to be one of the exceptional, but silent, benefits from GM crop production.

Conflict of Interest

I declare no conflict of interest.

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After more than 25 years of research and development on the genetic modification of a wide range of crops for food and fodder, China has reached a decision point as to whether it should accept, reject, or go slow with the use of genetically modified (GM) technology to produce the food and feed needed to sustain its population growth and economic renaissance. Here, we report a consumer survey on GM food that includes input from all provinces in China. Chinese consumers were surveyed for their awareness, knowledge, and opinion on GM food. The survey resulted in 11.9, 41.4, and 46.7% of respondents having a positive, neutral, or negative view on GM food, respectively. A minority of respondents (11.7%) claimed they understood the basic principles of GM technology, while most were either “neutral” or “unfamiliar with GM technology”. Most respondents (69.3%) obtained their information on GM food through the Internet and 64.3% of respondents thought that media coverage was predominately negative on GM food. The reasons given by consumers in favor of, or against, the use of GM food, were complex, as seen by the response of 13.8% of respondents who felt GM technology was a form of bioterrorism targeted at China. China’s Ministry of Agriculture and the science community generally expressed a positive attitude toward GM food, but the percentage of respondents that trusted the government and scientists was only 11.7 and 23.2%, respectively. Post-survey comments of respondents made suggestions on how the industrialization of GM technology might impact the future of China’s food supply and value chains. Finally, the impact of emerging technologies like genome editing and genome-edited organisms (GEOs) on the GM food debate is discussed.

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Introduction.

Genetically modified (GM) technology is a highly controversial topic for today’s global food consumer. The commercial development of GM crops began in 1996 with GM corn and has expanded every year with the cultivation of GM crops. In 2016, global land use for GM crops reached 185.1 million hectors. 1 Although GM foods had helped sustain the nutritional needs of human beings and farm animals and mounting evidence showed that GM foods were substantially equivalent to traditionally bred food sources, it has also sparked fierce debate about its safety. This has generated worldwide interest in finding a common and harmonious narrative to deal with new opportunities and challenges of biotechnology. A recent review of public perceptions of animal biotechnology, 2 provides an excellent context for understanding public knowledge, attitudes, and perception of GM Food in China.

China comprises 20% of the world’s population, 25% of the world’s grain output, 7% of the world’s arable land, and 35% of the world’s use of agricultural chemicals. 3 Consequently, China faces risks to its food security and pollution of the environment. The government has invested heavily in research and development of technologies to improve quality and increase the output of its foodstuffs, especially grains. GM technology provides a such feasible approach 4 , 5 to realize these goals. As the complexity of the GM issue mounts, the controversy surrounding GM food has moved farther away from science. While China’s president calls for its scientists to “boldly research and innovate [and] dominate the high points of GMO techniques”, 6 the people of China are largely opposed to GMO foods, but are not sure why. 7 Thus, this nationwide survey on the current Chinese public perception of GM food should be helpful to policy-makers, technology developers, as well as to consumers.

Consumer attitudes about GM food are complex and interwoven with the consumer’s knowledge of the science, lifestyle and public perception. Since 2002, surveys have been conducted in China on public acceptance of GM food from the perspective of consumer behavior, such as intent to purchase, presence of GM markers, and sensitivity to price point 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 (Table 1 ). There has been a general lack of fundamental studies on the public’s scientific perception and policy interpretation of GM food. Moreover, the scope of previous surveys has been limited to a few of the largest cities in developed areas of China, with little or no coverage of rural areas. In all cases, the number of respondents in most of these earlier surveys was less than 1000. This study summarizes the status of GM food in China and provides the results of questionnaires that surveyed consumers from every province on their knowledge level, present attitudes, and future thoughts of GM food in China. A statistically relevant sample size of 2063 questionnaires were satisfactorily completed. The findings in this survey provide insight into Chinese consumers and offer a possible path for “smart” industrialization of GM technologies in China.

General consumer attitudes of GM food

The first six questions of the survey asked about the respondent’s background, followed by 18 questions that addressed their awareness, knowledge, and opinion on GM Foods. The seventh question asked, “In general, will you support GM food?” The percentage of those who supported, opposed or were neutral were 11.9, 41.4, and 46.7%, respectively. These results suggest that the overall attitude of the Chinese consumer is cautious of GM food.

GM technology was first introduced in the pharmaceutical industry and then applied to agriculture. Did the public’s skepticism originate from GM food safety or GM technology itself? Question #8 was designed to address this question. “If GM technology is applied in medical area to produce medicine, such as insulin and hepatitis B vaccine, what is your opinion?” The percentage of those who supported, opposed or were neutral to GM pharmaceuticals was 46.8, 12.8, and 40.4%, respectively. Support for GM pharmaceuticals was higher than that found for GM food and again, there were many in the neutral category. This result suggests that some respondents were against GM food but not against GM technology. Still, there were 12.8% of respondents that took a negative view about GM pharmaceuticals, although they may not have known that the insulin and hepatitis B vaccine widely used today are GM-derived pharmaceuticals.

Since 2002, the year when China implemented legislation mandating the labeling of GM food products, numerous surveys in China were carried out to gain insight into the public’s attitude to GM food. The results from these early surveys were compared to the results of the present survey (Table 1 ). Significant differences were found between the surveys, likely due, in part, to differences in the number of respondents, where they resided, and when the surveys were conducted. The results were also difficult to interpret because of differences in content of each survey and in the respondents. The respondents in the surveys represented the public, media, private enterprise and government. Overall, the trends were interesting even with this inherent variability, and reflected consumer preferences about GM food. The ratio of “support” vs. “oppose” GM food was used as a measure to compare the different surveys (Table 1 ). This measure suggests an interesting trend in that the ratios before 2012 were larger than 1.0 (with one exception) and thereafter, were less than 1.0. The survey reported here gave the lowest ratio, 0.29. In summary, the initial positive attitude towards GM food in 2002 generally decreased in subsequent years.

To gain further insight into consumer attitudes toward GM food among the respondents, six factors were selected as research variables. As shown in Table 2 , respondent’s attitudes towards GM food were correlated to their age, sampling location, educational level, major in college and income. A negative attitude toward GM food was more frequent among those respondents born before 1969 (59.3%). The public-sector group from Western China reported 51.3% against GM food, compared to 29.7% from those located in the center and in northeastern China. The percentage of those respondents with college degrees who supported GM food was 9.5%, which was the lowest number relative to any other group. The percentage of respondents with a positive attitude was higher for those with a science background (14.1%) compared to those with a liberal arts background (7.5%). The percentage of respondents with a negative attitude was higher (51.6%) with those who reported an annual household income above one million Chinese Yuan (RMB), compared to those with an annual household income below 80,000 RMB (34.2%). Gender was not found to be a factor in shaping attitudes towards GM food.

We further queried the state of Chinese public opinions on GM food and determined the main reasons for the either their support (Question #9) or opposition-against (Question #10) to GM food, from what was known previously. The statistical results showed that the total number of “support” and “oppose” was 3248 and 4751, respectively. This demonstrates again that the public is cautious about GM food. The relative percentage of choice, “frequency” (defined as the number in support or against divided by the total number in the respective area) is listed in Table 3 .

GM technology is potentially a paradigm shift for farmers in developing countries and is an important tool in the toolbox for addressing global challenges, such as persistent poverty, climate change, and the challenge of feeding 9.7 billion people by 2050. Some studies suggested that efforts to change consumer perception about GM food should address risk perception factors and promote the beneficial effects of biotech crops. 24 As a nonpartisan, nonprofit organization, Intelligence Squared U.S held a TV debate on December 4, 2014 on whether the world is better off with or without GM food. The discussion was whether GM food is safe, how it impacts the environment and can it improve food security). Both the positive and negative sides had experts debating for or against GM food. Among the attendees who were present, the percentages in favor or against “genetically modified food” were 32 and 30%, respectively, before the debate, but this changed to 60 and 31%, respectively, after 100 min of debating the topic. This result suggests that efforts to change public perception about GM food should address risk perception factors and promote the beneficial effects of biotech crops. It should be noted that some opponents of GM food have started to rethink their prior attitudes about GM food. 25 On the other hand, some research suggested that many opponents are evidence-insensitive and will not be influenced by arguments about risks vs. benefits. 26 Food Evolution, a 2017 documentary film directed by Scott Hamilton Kennedy and sponsored by the Institute of Food Technologists (IFT) vividly illustrated the polarizing worldwide debate, “for and against” GM food. Its fact based, story telling narrative delivered a powerful educational message on new technologies and the process of acceptance by consumers. People involved in the making of the film tried to encourage audiences to think critically and reexamine their information sources and beliefs regarding GM food.

Factors shaping public perception of GM food

How much did the public know about GM technologies? Some earlier studies 12 , 17 , 27 , 28 , 29 based their conclusions on individual and subjective questioning, and only asked the respondents: “Do you know GM technologies?” The authors in this study agree with Hallman 30 that the self-reported awareness of GM does not necessarily mean respondents understand the principles and purpose of GM food. Thus, Question #11 was asked in this survey: “Do you know the principle of GMO such as introducing foreign genes, genetic recombination and gene expression? “

The result of our survey showed only 11.7% of the respondents self-reported that they were familiar with the general scientific principles of GM technology, contrasted to 49.5 and 38.8% saying they know something and nothing, respectively, about the subject. In the absence of sufficient understanding of biotechnology, the public’s attitude towards GM food safety can be misleading. Thus, we carried out a correlation analysis between the public’s perception (Question #11) and attitudes towards GM technology (Question #7). The results are given in Table 4 .

The design of this questionnaire was based on the following hypothesis: The opinion of consumers to GM food will be related to their knowledge of GM food. This was confirmed in this survey. There were positive correlations between “know a lot” and “support”, “know nothing” and “oppose”. At the same time, there were negative correlations between “know a lot” and “oppose”, “know nothing” and “support”. The lower the understanding of GM technology, the more hesitant the respondents were to accept GM food. These results also highlight the influence and importance of studies on the public perception of science in China.

Chinese food safety scandals have been a growing concern for Chinese consumers in recent years. The incidences of illegal “gutter oil” used in cooking, pesticide residue contamination, use of feed additives and polluted water along the food chain are common problems and even with proper regulatory oversight, the risk for criminal activity is ever present. The consumers in China, as well as consumers in other parts of the world, are increasingly risk adverse and seek out “clean, natural food”. Thus, the perceived risk of GM food was heightened because of these scandals, even though perceived risk of GM food is mostly based in perception rather than in practice. How deeply does the Chinese public think about the safety of GM food? Question #12 was asked to reflect this: “Compared to other food safety issues in China, such as illegal cooking oil, pesticide residue, feed additive and water pollution, your concerns on the safety of GM foods are?” The result illustrated that 20% of respondents thought the safety issue of GM food was more severe than other issues compared 31.8% of respondents thought “nearly the same”, 22.5% of respondents thought “not as severe” and 25.7% of respondents “have no idea”. These results mean that more than half of the respondents were concerned about the safety of GM food, of which 20% were deeply concerned, above and beyond any other food issue facing China.

Source of information on GM foods

The respondents were asked, “Have you actively searched for information on GMO’s using web search, reading books and verbal inquiries after graduation?” (Question #13). The result showed that 38.7% chose “yes”, compared 36.2% who chose “No, but I really care about GMO”, and lastly, 25.2% who chose “No, I don’t care about GMO”. When asked, “How do you acquire information on GM Food?” (Question #14), the result showed that 69.3% of respondents acquire information from the Internet as compared to 45.3% from television, 27.8% from books and periodicals, 22.8% from communication from relatives and friends, 22.4% from learning at school and 9.6% from public lectures. It is well known that GM food is a complex issue, and information from the Internet is often unverified and inaccurate. Thus, there is an urgent need in China to educate the public on GM technology and GM food by providing balanced, evidence-based perspectives of the technology to consumers through presentations, written materials, documentaries and educational courses that are made widely available through various media. The government can play a key leadership role by supporting educational programs, particularly targeting young people. It also crucial to put in place safeguards and the communication needed to ensure to the public that GM foods are thoroughly tested and regarded as safe. Regulatory groups worldwide must demonstrate their ability to ensure the safety of “new” foods and food ingredients, in a harmonious and transparent manner. Another question (#15) asked was, “Based on your experience, you have found that the media reports and Internet rumors about GM Food generally tend to be?” The results showed that respondents answered the question of media atmosphere as negative (64.3%), positive (11.5%) or neutral (24.2%).

Other studies have shown that the public tends to build upon its negative impression of GM food even in the face of positive information. 31 , 32 The lack of understanding of the principles and benefits of GM technology, make the general population more susceptible to negative media reports. The debate around GM food has become increasingly one-sided in recent years, with activists spreading misinformation via social media about the human health dangers of GM food as well as the negative environmental impact of GM crops on transitional agricultural eco-systems. Additional negative information on social media had a great impact, driving down the willingness to accept GM food. This led to food-centered non-governmental organizations (NGO’s) directing their attention to generating debates, educational packages and other formats to reach out to the general public (e.g., work of US based Farmer’s and Rancher’s Association and IFT). Research supported by the Chinese Academy of Social Sciences showed that rumors about food security accounted for 45% of all Internet rumors which severely influenced the public’s trust. 33 Our study also attempted to probe into the public attitudes toward rumors about GM food on the Internet. For example, in China, rice is the main staple food for 60% of its people, and hybrid rice accounts for about half the planting area of rice. Rumors were spread that hybrid rice is a GM crop. Through self-interest, some non-GMO food producers condemned GM food with malicious gossip and misplaced nationalism, fomenting the notion that GM technology originated in the U.S. as a form of bioterrorism against China. What did the public think about this? (Question #16, 17 and 18). The result (Table 5 ) showed that 15.8% of respondents think that hybrid rice is one kind of GM crop, 25% of respondents think that there is unfair business competition with GM food, 13.8% of respondents agree that GM technology maybe considered as bioterrorism to China. These results pointed to an underlying problem that the debate on GM food in China has deteriorated. It is worth mentioning, however, that more than half of the respondents (54.4%) believed that debate on GM food should be based on science. This is the basis for why the debate about GM food should be based on scientific evidence.

Since the GM food debate should be evidence-based, the public needs to put more trust in scientific explanations and research data that can be understood by the average consumer. Many scientists including 110 Nobel Prize winners openly support GMO technology in the recent years. The 2016 Report 34 issued by the U.S. National Academies of Sciences, Engineering, and Medicine found “no substantiated evidence of a difference in risks to human health between currently commercialized genetically engineered (GE) crops and conventionally bred crops.” What do the American public think about the above report? A survey carried out by University of Pennsylvania 35 showed that only 22% of those surveyed agreed that scientists have not found any risks to human health from eating GM foods, while 48% of the people disagreed with that statement. What is the situation in China? The result (Question #19) showed that 23.2% of the respondents chose to “believe in biologist’s opinion” compared to 45.5% who chose to “do not trust biologist’s opinion” and 31.3% who chose to “have no idea about this.” This result reflects that scientists are “under suspicion” on the issue of GM food both in China and the US. The film, Food Evolution, and other educational materials are helping to change this viewpoint. “What is the most important information that the public wants to know about GM food?” We asked this question (#20) in the survey. The result (Table 6 ) showed that more than two out of three respondents (68.9%) wanted to know more about the safety of GM food.

Public perception and attitude to policy

The Dean and Shepherd study 36 found that participants’ perceptions of risk lessened when governmental agencies presented a consistent message to the public. China’s Ministry of Agriculture claimed in 2016 that there is no substantiated evidence showing that genetically modified foods are unsafe during the past 20 years of commercial cultivation. But according to our survey (Question #21), only 11.7% of respondents thought that the government’s statement was an “authoritative interpretation”, compared 10.9% who chose “that is concealing the truth” and 77.4% who chose “No evidence now does not mean no evidence in the future. We should still be cautious to GM foods.” To a certain extent this result demonstrates that the public does not consider the government as a credible source of information on the issue of GM food.

Question #22 addressed the following, “What kind of GM crops were approved by the government to cultivate and produce in China?” Seven options were provided, including corn, rice, wheat, soybean, cotton, rape, and papaya. Only GM cotton and GM papaya have been approved for commercial cultivation in China. According to our survey, disappointingly few, only 1.2% of respondents chose the right answers. Apparently, government sources of information on GM crops has not been effective in educating the Chinese public about GM food.

In Question #23, the respondents were asked “What do you think of the force of government supervision for the production and import of GM food?” The result showed that 47.1% of respondents felt that the government should “strengthen supervision force, it is best to totally ban the GM foods”, compared that 43.3% felt “supervision force is appropriate” and 9.6% felt “supervision force is too tight.”

“The Chinese Ministry of Agriculture claimed that GM crops and GM food are advanced technologies that can serve as the foundation of a new industrial sector with broad implications for human health and wellbeing. As a large agricultural county, China should have a place for transgenic (GMO) technologies. What do you think about this?” (Question #24) The result showed that only 28.8% of respondents “support” this policy, compared 18.9% that chose “opposed” and 52.3% that chose “neutral”. In the face of widespread suspicion and misinformation about GM foods, more effort is needed to gain the confidence, trust and support from the public domain.

GM crops and the foods derived from them are considered the most immediate solution to alleviate global hunger and malnutrition. The benefits of GM crops such as greater productivity, reduced need for pesticides and herbicides, increased economic benefits for large and small farmers alike, have been extensively reviewed. 37 However, public attitudes toward GM food from country to country in different regions of the world continue to vary. The recent review by Van Eenennaam and Young 2 gives an excellent summary of the complexity of surveying and interpreting global public opinion on GM foods. In short, the authors noted the negative view of GM food in Europe, was exacerbated by the bovine spongiform encephalopathy (BSE) crisis first in the late 1980s and again in the 1990s. It was thought that GM technology might be used to mask the effects of poor housing of animals, not to mention the sense of supporting global agro-business rather than smaller family farms which are typical in Europe. In contrast, the United States, Canada and some Latin American countries (namely Brazil and Argentina) have widely adopted GM crops. Brazil is the second only to the United States in the land used for GM food crops. A review of acceptance, policies and actions in the African countries illustrated the complex and myriad issues that slow the adoption of GM food, thereby deleteriously impacting African countries. 38 Though the progress is slow, there seems to be a new receptiveness for GM food amongst some of the African countries. It is interesting to note that a study in Africa in 2005, showed that of the 7000 people surveyed, 80% did not know the meaning of the word “biotechnology”. 2 In Asian countries, it has been noted that China’s initial lead position in GM food has slowed over time due to global resistance 39 to GM food. However, signs of acceptance of GM food in China are encouraging. 40 , 41 Finally, Van Eenennaam and Young 2 compared China with other Asia countries (India, The Philippines) where bans on GM foods or vandalism on GM crops have occurred. On the other hand, Bangladesh has successfully adopted insect-resistant GM eggplant and has become a success story for the adoption of GM crops. 2 , 42

In our analysis, public attitudes toward GM food continue to swing widely across China from opposition to acceptance. On one side, some socialistic organic farmers, environmentalists and NGO’s have questioned the security of GM food, with some even calling for a ban on growing most GM crops. On the other side, agricultural specialists and biotech industry representatives highlight the benefits of GM technology to concerned consumers. The survey reported here was intended to be very broad in the type and range of questions asked. The authors plan to follow up with a more focused survey on safety issues related to GM food. Transparent and harmonious regulatory oversight is helping to further ensure the safety of GM technology and GM food but this must be understood and agreed by consumers as well as scientists. We should not expect, however, any convergence of opinions in the very near future. Based on the results of this study, suggestions about the future industrialization of GM technologies and GM food in China are presented as follows.

Strengthen communication to the public, making order out of confusion

Chinese consumers, in general, were found to be unfamiliar with GM technologies and the benefits they provide. They were also skeptical of scientists and the government on the topic of GMO, GM technologies and GM food. Fortunately, there is consensus in the public domain that more discussion on GMO and GM technologies is needed to better understand the scientific and social implications of GM food. Accordingly, public lectures and other educational formats need to be expanded in China to help the public develop evidence-based attitudes about GM foods. Until public doubts about GM food are addressed in a balanced and evidence-based manner, it will be difficult for China to develop sound policies and programs that will benefit the agribusiness industry and consumers. All forms of the media in China should be encouraged to incorporate scientific facts in their reporting and to discourage exaggerated reports and “fake” news. There should be a constructive vision and plan for building a future society that includes rational attitudes and a foundation for a food secure global society with adequate safety safeguards in place.

Government work should transform passivity into initiatives

China’s central government recently issued a document calling for more research, development and supervision of agricultural GMO and GM technologies, and the careful promotion of GM food that is safe, affordable, and healthy. From the result of the surveys taken in recent years, it was found that the percentage of respondents who opposed GM food is on the rise, and significant effort is needed to overcome that trend. The issue of GM food is very sensitive in China, GM policies have wavered among concerns over the bio-safety debate and development goals, such as food security, poverty reduction and the approval of transgenic commercial planting that was brought to a halt in recent years. In the long run, GM policies will influence the international competitiveness of the seed industry and agricultural development in China. As mentioned above, the safety of GM food should be based on science, and a modern society should not judge the safety of one kind of food by the way of a referendum. The government should enhance communications with the public and strive for the understanding and support of the public for China’s GMO policy.

Respect public opinion, improve gradually

Throughout history, many innovations have experienced both headwinds and tailwinds before being accepted by society. There is a persistent gap between expert knowledge of scientific issues and public perception of these issues. The conclusion of natural sciences usually is only truth, although the culture and attitudes can be diversified, being influenced by religious beliefs and/or political parties. Differences in public opinion towards GMO, GM technologies, and GM food should be respected. What is needed is government leadership in constructing a transparent system for evaluation of these technologies for commercial use while, at the same time, upholding the public’s right to have a choice by labeling GM food products. This will enable the public to make their own choices about GM food.

Lurking in the background, however, are new technologies that can produce genetic modifications in plants and animals in ways that are different and more precise that traditional GM technologies. The CRISPR-Cas9 genome editing technology 43 together with new signal DNA base editing 44 and RNA base editing 45 are currently revolutionizing the fields of agriculture, medicine and basic research. Unlike the traditional GM technology that adds foreign DNA to the recipient organism as part of the process, genome-editing, and base-editing simply switch out mutated or otherwise undesirable DNA bases that detract from the overall fitness, productivity, quality and usefulness of the organism, in question. Regulatory policies in the United States were written nearly 30 years ago and do not address the safety of genome-edited or base-edited organisms (GEOs). Currently, regulatory agencies are declaring these “edited” organisms and foods as safe and they are exempt from testing and labeling requirements. GM technology opponents have already spoken out against these forms of genetic modification and now that public must make their voices heard.

Only time will tell if foods derived from GM technology or genome-edited and base-edited organisms will be the best solution to achieving food safety, security, and sustainability. At least for GM foods, the lack of any documented adverse effects is encouraging. With the improvement of the scientific literacy, the debate about GM food should return to a rational one and one that will shape the future Chinese society.

Questionnaire development

The initial design, order and questions used in this questionnaire were based on both past information 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 and input from 40 interviewees, representing consumers, agricultural officials, seed companies, farmers, biologists, and sociologists. From this input, 28 questions were generated as a pre-survey test to address the public perception of GM Food. The pre-survey was carried out in March 2016 with 100 respondents. Based on their feedback, the questionnaire was refined further into the final survey of 24 questions used in this study. The goal was to gain insight into the following four questions through this survey:

In general, what are consumer’s attitudes to GM food in China?

How does public perception of GM food correlate to the science behind GM food?

What is their source of information on GM foods and how does this source influence their perception?

How does the public’s perception and attitude correlate to policy?

The survey was designed to offer a range of questions to determine the respondent’s demographics, educational level, knowledge of GM food. The survey was conducted in both public and private meeting rooms between May 2016 and October 2016. The questionnaires were distributed altogether in 38 different venues. All questionnaires were handed out to individuals and collected after 10 min by Dr. Kai Cui.

Participants

A summary of the participants in the survey is given in Table 2 . They were all Chinese citizens over the age of 15, from 193 cities and, in total, included representation from all 31 provinces in China.

Approach to distribution

The questionnaires were distributed as part of a course on investment and finance. The course was conducted by the sole instructor, Dr. Kai Cui. After the course participants became familiar with the instructor (1–2 days) and understood the purpose of the course, they were administered the questionnaires. While instructing the course, students were asked to fill out a questionnaire to give their opinions on the level of understanding of GM technology in China from a consumer’s perspective. A total of 2200 questionnaires were distributed during this 6-month period with 2063 questionnaires satisfactorily completed.

Statistical analysis

Analysis of the survey results was done using the software program package - Statistical Product and Service Solutions (SPSS)19.0.

Data availability statement

A sample of the questionnaire. translated into English, is available in supplementary information at npj: Science of Food’s website. The completed 2063 questionnaires and the resulting database for the statistical analyses are in mandarin are not publicly available but can be made available from the corresponding author on reasonable request.

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Acknowledgements

Project supported by the National Natural Science Foundation of China (Grant No. 7157317). The corresponding author would like to express the gratitude to Hui Meng (Professor of Eastern China Normal University), Dr. Xiaojun Lv (Associate Professor of Shanghai Jiaotong University) and Dr. Yan Liu (Associate Professor of Indiana University) for their suggestions in the design of the questionnaire and also acknowledge Beina Zhang and Yongyong Yang (Master students of Shanghai Normal University) for their support in data analysis. The co-author would like to gratefully acknowledge Professors Raymond Rodriguez, Professor Alison Van Eeneenaam and Christine Bruhn from the University of California, Davis, for their editorial assistance in the preparation of this manuscript. Project supported by the National Natural Science Foundation of China (Grant No. 71573173).

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Dr. Kai Cui, corresponding author, designed the questionnaire and delivered it to groups he met with in China. He secured the help for the statistical evaluation of the respondents in the survey. Dr. Sharon Shoemaker provided advice and collaboration in the fundamentals and consumer attitudes of GM technology. She was Dr. Cui’s mentor while he was at the California Institute of Food and Agricultural Research (CIFAR), UC Davis, and she provided basic understanding on the topic of GM Food and biotechnology, in general. She also contributed to the writing and editing of the manuscript in English.

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Correspondence to Kai Cui .

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Cui, K., Shoemaker, S.P. Public perception of genetically-modified (GM) food: A Nationwide Chinese Consumer Study. npj Sci Food 2 , 10 (2018). https://doi.org/10.1038/s41538-018-0018-4

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Received : 17 August 2017

Revised : 28 January 2018

Accepted : 09 April 2018

Published : 05 June 2018

DOI : https://doi.org/10.1038/s41538-018-0018-4

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