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Ohio State University Extension


Understanding Genetically Modified Foods

Revised by: Robin Ralston, Program Director, Center for Advanced Functional Foods Research and Entrepreneurship, Food Science and Technology; and Shawna Hite, Program Specialist, Family and Consumer Sciences

What are genetically modified organisms in relation to foods?

A genetically modified organism (GMO) is an organism whose genetic structure has been altered by adding a gene that will express a desirable trait. This is often referred to as ‘gene splicing’. This new trait might improve a crop or organism’s nutritional qualities, make a crop resistant to herbicides, or protect a crop from pests. The overall goal is to make the crop more desirable for the producers or consumers of the end product. Foods that contain GMOs are often called genetically engineered foods or biotech foods. We will refer to these as genetically modified (GM) foods throughout this fact sheet. 

Launched in 1994, the Flavr Savr Tomato was the first U.S. Food and Drug Administration (FDA)-approved GM food available on the market. This tomato had a new gene that prevented the breakdown of the tomato’s cell walls, thus extending its shelf life. While there was no scientific concern over its safety, the tomato was removed from the market in 1998 due to consumer concerns (Bruening and Lons, 2000). Today, cotton, corn and soybeans are the most common genetically engineered crops in the United States (USDA, 2015). About 80–95% of these crops are genetically engineered. These crops have been altered to have increased insect resistance or tolerance to herbicides. There are currently no foods on the market that have been genetically modified to improve nutritional quality.

How does genetic modification occur?

There are four main ways in which scientists can genetically modify the crops and organisms we use for food:

  1. The most common form of modification is selective breeding. In selective breeding, two strains of crops or organisms are bred to produce an offspring that has a specific feature. Selective breeding has been used for thousands of years to enhance desired traits in plants and animals, and impacts 10,000–300,000 genes (Rangel & Maurer, August 2015). This form of genetic modification is not usually included when we discuss GM foods. 
  1. A second form of modification is mutagenesis. Mutagenesis is only performed on crops. In mutagenesis, crop seeds are exposed to chemicals or radiation, which causes them to rapidly mutate. These mutations are random and uncontrolled, but researchers observe how the resulting crops grow. Those crops with desired traits are kept and further bred, while crops with unwanted resulting traits are discarded. It is unknown how many genes are impacted (Sherman et al., 2015). This form of genetic modification is also not usually included when we discuss GM foods. 
  1. RNA interference is one of the modern forms of GM. In RNA interference, genes that cause undesired traits are silenced. This silencing of genes removes any unwanted trait(s) from the crop or organism, and impacts only 1 or 2 genes (Argawal et al., 2003; Sherman et al., 2015). 
  1. Another form of modern GM is transgenics. In transgenics, a gene is taken from one species and implanted into a specific genetic location in the receiving crop or organism. Transgenics provide the recipient crop or organism with a desired trait that it would not otherwise have, and impact only 1 to 4 genes (Nicolia et al., 2014; Sherman et al., 2015).

The remainder of this fact sheet will discuss RNA interference and transgenics because these are the forms of GM which have had questions raised regarding their impact on safety and health in foods.  

Who regulates GM foods?

Current U.S. regulations covering GMOs involve three federal agencies: The U.S. Department of Agriculture (USDA), the Environmental Protection Agency (EPA), and the FDA.

Through the Animal and Plant Health Inspection Service, the USDA’s role is to ensure the safety of GMOs related to plant health (USDA, 2016). Developers of GM crops must apply for a permit, which requires addressing the potential risks and the possibility of the organism spreading into the environment.  

The EPA regulates any GMO that contains a pesticide as part of its genetic makeup (EPA, 2016). The EPA defines safe levels of the pesticide and requires manufacturers of the organisms to address short- and long-term consequences of the pesticides on humans, livestock and the environment. The EPA only regulates the genetic material incorporated into the plant; it does not regulate the plant itself.

The FDA regulates the safety of all GM crops that are consumed by people or animals (FDA, 2015, How FDA Regulates). This role was defined when the FDA established a policy in 1992, which defined most GM crops as “substantially equivalent” to non-modified crops under the Federal Food, Drug and Cosmetic Act. In doing so, the agency defined all GM foods as “generally recognized as safe.” By recognizing GM foods as substantially equivalent, the FDA ensured they would provide the same oversight and regulation over GM foods as they provide over non-GM foods in the United States (McHughen & Smyth, 2008). Under its voluntary Plant Biotechnology Consultation Program, the FDA evaluates the safety and nutritional characteristics of a GM crop before it is marketed. The consultation begins with a safety assessment, conducted by the product manufacturer. This assessment compares the levels of nutrients in the GM crop to conventionally grown crops. It also addresses whether products made from the GM plant are potentially allergenic or toxic when consumed. Lastly, unique qualities of new genetic traits are identified. FDA researchers then assess the safety evaluation, along with a review of their own records, scientific literature, and other publicly available data. 

What are the benefits of GM foods?

GM crops are theorized to reduce production costs due to reduced chemical and mechanical needs in planting, maintenance and harvest. For example, a recent meta-analysis of 147 corn, maize and cotton production studies showed a 21 percent increase in crop yields for those using GM technology. The analysis also showed an average profit gain of 69 percent for GM-adopting farmers, with those farmers in developing counties benefiting the most (Klumper & Qaim, 2014). It is possible that these cost savings could be passed on to the consumer. 

There are potential nutrition benefits as well. GMO technology allows for the creation of plants that are more nutrient dense. However, there is only one product the FDA has reviewed that focuses on nutrition and health: soybean oil that is high in omega-3 fatty acids (a nutrient that is traditionally under-consumed in the United States) rather than omega-6 fatty acids. At the time of writing in summer 2016, this oil is still being developed and is not yet available on the market (FDA, 2016). Another GM product termed “golden rice” contains beta-carotene (a source of vitamin A) and iron. Golden rice is directed toward developing countries with deficiencies in these nutrients, which can cause childhood blindness and anemia. Because rice is a dietary staple in most developing countries, golden rice could potentially help reduce these nutrient deficiencies. However, there is currently no nation planning to grow golden rice (Sherman et al., 2015). 

Recent FDA consultations that could also offer consumer benefits include GM apples and potatoes with decreased browning after being cut, and potatoes with lower acrylamide (a potentially harmful chemical) formation when heated (FDA, 2016). At the time of writing in summer 2016, the GM potatoes are still making their way through the approval processes and are not yet available for consumer purchase. Small quantities of the GM apples are expected to be available after the 2016 harvest.

What are the health concerns of consuming GM foods?

There is a significant gap in the opinions of scientists compared to the general public about the safety of consuming GM foods: 37 percent of consumers feel that GM foods are safe, while 88 percent of scientists say that GM foods are safe (Funk, 2015). The most common concern with GM foods is the risk of allergic reactions. More than 90 percent of food allergies occur in response to specific proteins in milk, eggs, wheat, fish, tree nuts, peanuts, soybeans and shellfish (FDA, 2015, Food Allergies). The risk for allergic reaction stems from the potential for a protein from one allergenic food being incorporated into another food that is not known to cause an allergic reaction. For example, if an individual who has a known allergy to peanuts unsuspectingly consumed a GM food that contained the peanut’s allergenic protein, it is possible that the individual would experience an allergic reaction. 

This concern has been addressed by the FDA’s consultation process. The FDA requires scientific evidence that no allergenic substances have been incorporated into GM foods. If this evidence cannot be presented, the FDA requires a label on the product to alert consumers of the possible presence of an allergen (FDA, 1992, Statement of Policy).

Concerns have also been expressed over the possibility of gene transfer from GM foods to cells within the human body, but the risk of this is very low and the risk of it having a negative impact on human health is even lower (World Health Organization, 2014).

How do our bodies digest GM foods? 

Genes code for the production of specific proteins. All proteins consist of amino acids. Proteins differ from one another based on the sequence of amino acids. When humans consume a GM food that has had a gene spliced into its genetic structure, we are consuming the protein for which that new amino acid sequence codes. Once we have consumed the protein, the protein from the GM food is digested in the same way as other proteins we consume. During digestion, the body breaks down all bonds between protein’s amino acids, reducing the protein to individual amino acids that can be used in the body. The cells in the human body cannot detect if a gene or protein is “natural” or from a GMO during digestion because the protein is completely unbound from the original plant.

Why would the FDA approve GM foods without clinical trials?

Clinical trials require researchers to expose one group to a specific condition while another group is not exposed to that condition. Clinical trials to investigate the impact of GM foods on human health are difficult to achieve. Because roughly 60–70% of processed foods in the United States contain a GM ingredient, it is difficult to achieve the comparison GM-free diet (World Health Organization and Food and Agriculture Organization of the United Nations, 2001). In other words, it would be difficult to have some participants in a research study consume a diet that did not contain any GM foods because these foods are so prevalent in our modern food system. 

In addition, because some conventional foods can also have unfavorable health effects, it is difficult to measure the effect of the GM food versus the unfavorable conventional foods, such as those foods containing high levels of saturated fat or simple sugars. Additionally, the clinical trial would have to take place over a very long period of time to reflect a lifetime of consumption of GM foods. 

Are GM foods labeled?

The FDA previously required labeling of GM foods in only these following situations: 

  1. If a food was significantly different from its traditional counterpart in appearance or use
  2. If the nutritional properties of the food were significantly altered 
  3. If an allergen was present that consumers would not expect (for example, a peanut protein in a corn product) (FDA, 2015, Guidance for Industry) 

However, a new federal standard for the labeling of GM foods was signed into law in July 2016 (Addady, 2016). Once the details of the labeling rules are written over the next two years, a food that contains GM ingredients will be required to have a text label, symbol, or electronic QR code indicating that it contains GM ingredients. Previously, Vermont was the only state to require GM food labeling, but this federal law will supersede state GM labeling laws, including Vermont’s law. Until the details are completed and the new labeling law goes into effect, the FDA still encourages industry to follow its list of guidance for GM food labeling (FDA, 2015, Guidance for Industry).

Those in favor of GM food labeling emphasize that labels provide:

  1. A risk management tool for any future unexpected adverse health effects
  2. Information essential to consumers’ right to know what is in their food 
  3. The same mandatory laws that have been established in at least 64 other countries—including those in the European Union 

Opponents of labeling emphasize the logistical challenges and expense of labeling, and the fact that no significant differences have been detected between conventional foods and GM foods. 

While the nonprofit Non-GMO Project offers a label for products they have verified to be “non-GMO” (Non-GMO Project, 2016), currently, the only federally regulated food label that ensures the absence of GMOs in food products is the “USDA Certified Organic” label (FDA, 2015, Guidance for Industry). GMOs are prohibited in organic products. This means organic livestock cannot eat GM feed, an organic farmer cannot plant GM seeds, and an organic food producer is not permitted to use any GM ingredients. To meet USDA organic regulations, farmers and manufacturers must prove they are not using GMOs and are shielding their products from contact with outside GM materials (FDA, 2013, Organic 101). In addition, the FDA has created guidelines for companies who wish to voluntarily label that their food products are made with non-GM ingredients (FDA, December 2015, Guidance for Industry).

What questions still need to be investigated concerning GM foods?

There are many questions to be answered before GM foods can be identified as “good” or “bad.” Questions are being continuously investigated from multiple disciplines. Some general research questions include:

  • GMOs have potential to help prevent diseases. Can GM foods be used effectively to prevent disease in at-risk populations?
  • GMOs have potential to create inexpensive foods that contain high amounts of nutrients. Can this provide nutrient-dense food supplies for people with limited resources?
  • GMOs could allow production of more food from the same amount of cropland or less. What is the economic impact to U.S. and world agricultural economies?
  • GMOs could be developed so that plants can survive droughts or floods on lands that are currently unable to sustain crops. What are the impacts on environments and ecosystems if we bring this land into production?
  • GMOs have potential to reduce the amount of pesticides used on crops. Does this significantly reduce the environmental damage of pesticide use? 
  • GMOs can change the genetic makeup of foods we consume. Can we understand GMO interactions with body functions, other foods, pharmaceuticals, and allergies?
  • GMOs have been criticized for their possibility of creating “super weeds” or cross-pollinating with other non-GM crops. Can GM crops be sufficiently managed so that these risks are minimized?

Before any conclusions can be made about positive or negative impacts of GM foods on human health, research efforts must continue to address a multitude of questions. As our knowledge and use of GM foods increases, it is up to consumers to make informed decisions on GM food use in their personal lives. 

Additional Information 

This fact sheet is a revision of the original, which was written by Sereana Howard, Amanda Sokolowski and John Allred.

Originally posted Aug 23, 2016.