An Overview of GMOs

What to know about a controversial food topic

Controversy surrounding GMOs (genetically modified organisms) has led to misinformation on the internet, on television, and even in scientific literature. In fact, most scientists, consumers, farmers, corporations, government agencies, and other independent organizations can be divided into two categories: pro-GMO or non-GMO.

GMO myths such as "GMOs cause cancer," and "GMOs kill honeybees" lead to consumer skepticism and fear of “Frankenfoods.” For some people, the Non-GMO Project Verified label has become synonymous with healthy eating. Maybe you’ve purchased food with the recognizable label because of it or maybe you’ve purchased it without really knowing what it means.

To reduce confusion and make GMOs more understandable, we broke down the science (or lack of science) behind common GMO claims.


"Are GMOs safe?" is a broad question that encompasses thousands of scientific studies. It can be broken down into two categories: studies that show GMOs are safe, and those that show they are not safe.

Studies That Argue GMOs Are Safe

One meta-analysis (a cumulative analysis that draws from hundreds to thousands of peer-reviewed studies) confirmed that genetically modified (GM) corn has increased crop yields and poses no health risks to consumers. Published in the journal Scientific Reports, the meta-analysis reviewed more than 6,000 studies over two decades.

Other studies found that no one study has revealed health consequences in livestock in response to genetically modified animal feed. These studies show no evidence that GM animal feed is nutritionally subpar to non-GM feed, and no biological or toxicological significance was found in GM animal feed.

Most food safety authorities in the world, including the World Health Organization (WHO), the American Medical Association (AMA), the Food and Drug Administration, the United States Department of Agriculture, the American Dietetic Association, and more have released statements on the safety of GMOs.

For example, the American Dietetic Association claims that “agricultural and food biotechnology techniques can enhance the quality, safety, nutritional value, and variety of food available for human consumption.” The statement goes on to encourage the government, food manufacturers, and other qualified professionals to encourage GMOs in the marketplace.

Despite these studies, there is still debate over “Golden Rice,” which is genetically engineered to provide more vitamin A than spinach does, and has the potential to prevent blindness and death in underdeveloped countries whose populations depend on micronutrient-poor carbohydrates.

The essential findings in all of these studies and statements are:

  • there is no conclusive evidence that GMO foods are less nutritious than their non-GMO counterparts
  • there is no scientifically sound evidence that GMOs pose adverse health risks in humans or animals
  • there is no documented evidence of any illness or condition, including cancer, allergies, autism, celiac disease, asthma or other claims, caused specifically by GMO crops
  • some GMOs present promising qualities that could lead to a decrease in nutrition deficiencies

There is no reason to purposefully avoid GMO foods out of fear of harming your health.

Studies That Argue GMOs Are Not Safe

There is peer-reviewed research that shows GMOs may pose health risks to people and animals.

One of the most cited papers on the health risks of GM foods claims that genetically engineered potatoes harmed the health of rodents in the study. However, the study has been heavily criticized for flawed methods, inconclusive evidence, and false claims. One Harvard review further breaks down the potato study, citing other studies that disprove claims in the original potato study.

There are also literature reviews focusing on studies that claim GMOs pose health risks to humans. Like the potato study, however, many of these studies present shortcomings in the methods or experimental design, such as flawed statistics, poor control groups, lack of analyses, or inadequate sample sizes.

A review of 35 independent research studies disputes claims about various health risks of GM crops, noting that each one lacks some form of scientific integrity.

While there are studies with evidence that suggests GMOs are harmful to humans and animals, the evidence is inconclusive because of poor study design and/or implementation.

Environmental Impact

Again, the research in this category can be broken down into two categories: studies that show positive impacts on the environment, and studies that show negative impacts on the environment.

Positive Environmental Impact Studies

Most of the evidence available points to positive environmental contributions, such as reductions in pesticide, herbicide, and insecticide use, as well as improved biodiversity, water conservation, and healthier crop yields.


Biodiversity is simply the variety of life in the world or in a particular ecosystem or habitat. It’s incredibly important to preserve biodiversity to support different species of plants and animals in the world. When biodiversity is threatened, species begin to die off. GM farming has actually been shown to protect biodiversity.

One review states that "higher productivity on cultivated lands" is one result of growing GM crops, "whereas relatively non-productive agriculture practiced is highly destructive to biodiversity, since it consumes more land in an often destructive way.”

A meta-analysis on the impact of GMOs on biodiversity states that no clear trend in biodiversity was found. It goes on to say, “GM crops may actually increase crop diversity by enhancing underutilized alternative crops, making them more suitable for widespread domestication.”


As for pesticide use, most scientific literature on the subject points to decreased overall use of pesticides (which includes herbicides, insecticides, fungicides, and other disinfectants). On average, GM farming has reduced pesticide use by 37 percent and increased crop yields by 22 percent.

To illustrate this point, the reduction in herbicide use from 1996 to 2013 was just over 21.8 million kilograms—only for GM corn. Of course, the science points out that the greatest environmental gains are in developed countries such as the United States and Canada, where herbicide use is generally much greater.

Since GMOs allow farmers to make fewer spray runs and switch to reduced-or-no-tillage systems, greenhouse gas emissions have also been reduced. In 2013, carbon dioxide emissions went down by more than 2,000 million kilograms, attributed to the 785 million liters of fuel saved.

One group of agricultural economists took a different approach to the subject and asked, “What happens if we lose GMOs?” The answers they found include the following:

  • crop yields decrease and create a need for an additional 102,000 hectares of forest and pasture in the United States to be converted into cropland
  • greenhouse gas emissions increase significantly due to lower crop yields, more tillage, and more fuel use

Negative Environmental Impact Studies

There is limited evidence that GMO crops lead to an increase in a specific type of pesticide called glyphosate. The rise in glyphosate use began in 1998 and has slowly increased since then. Scientists guess that this is due to weeds building resistance to herbicides, similar to the way in which bacteria build up resistance to antibiotics.

Some researchers note that although GM crops may show resistance to glyphosate, total herbicide use on conventional crops has also increased over the last several years. Additionally, many conventional systems had resistance issues themselves in the 1990s.

There is a lot of conclusive evidence that GM crops benefit the environment in a number of ways, but only limited evidence that they could be harmful.

Economic Impact of GMOs

As with all controversies, there is always the issue of money. Do GMOs benefit the economy, or do they harm it? The research shows that in general, GMOs produce a positive impact on the economy.

Positive Impact Studies

Research suggests that the removal of GMOs from the marketplace could cause price increases of up to 28 percent for corn and increases as high as 22 percent for soybeans. That price change could cause actual food prices to rise 1 to 2 percent, or $14 billion to $24 billion per year.

PG Economics states that direct global farm income saw a benefit of $15.4 billion in 2015 due to GMOs. Since 1996, agriculture has benefited $167.8 billion.

Negative Impact Studies

While there isn’t any research that explicitly exhibits harm to the economy, some researchers are careful to point out that farmers may experience lost income due to lower market prices for crops.

Other research cautions that although GM crops prove to benefit the economy, things can change abruptly and it’s important to closely monitor the outcomes of GMO production.

Science says GMOs benefit the economy, as shown by over two decades of economic data. Just like other industries, however, agriculture can fluctuate in terms of economic benefit and drawback.

Consumer Perception

It’s no secret that consumers view GMOs through different lenses. Our perceptions are shaped by the opinions of people around us, media, and personal feelings toward food, health, and nutrition.


Part of the problem in misperceptions is that consumer knowledge hasn’t increased at the same rate as the adoption of GM technology, experts say. Consumers all over the globe display “limited understanding, misconceptions, and even unfamiliarity” with GM crops and food, possibly because they get most of their information from mainstream media and other internet sources—not directly from scientific studies themselves.

In a large consumer study implemented by the Food Policy Institute at Rutgers University, the majority of subjects said they knew very little about GMOs (48 percent) or knew nothing at all (16 percent). Just 5 percent of participants felt they knew a great deal about GMOs.

Researchers are concerned that consumers rely on sources like TV and magazines for GMO-related information, which can be “inaccurate, incomplete, or misleading, depending on the news outlet.”

In general, consumers tend to get their information from sources that aren’t peer-reviewed or fact-checked. This leads to misperceptions about GMOs and agriculture.

Other experts express worry that much of the GMO debate seems to be over politics rather than science.

Studies and Policies

Formal regulation of GMOs began in the 1970s, when both the scientific community and federal agencies realized the significance and potential of GM crops. The National Institutes of Health released the first official guidelines in 1976.

It's been noted that these guidelines aren't regulations, in that they do not have the same "force of law." (You will mostly see "should" written instead of "will" in these guidelines, for instance, meaning that the policies weren't strictly enforced or intended for immediate action.)

Changes Over Time

In 1984, the Coordinated Framework for Regulation of Biotechnology began to come together. It assumed the role of establishing regulatory responsibilities. Those responsibilities have changed over time—now the FDA, USDA, and EPA all hold their own jurisdictions over biotechnology and GM agriculture.

While the regulation processes surrounding GMOs are already extensive, some experts suggest there need be more oversight in certain areas to promote comprehensiveness such as industry interests, farmer interests, public opinion, consumer rights and interests, human health and food safety, food security, environmental protection, consistency and coherence of the regulatory framework, and ethical and religious interests.

Worldwide Practice

Some researchers think that current regulatory processes differ too much throughout the world. For example, the United States regulates GMOs based on the final product, whereas other countries might regulate GMOs based on the processes involved to reach the final product. These experts suggest that clearer regulations are needed.

The regulation of GMOs is extensive, but it’s not perfect. What’s most important is consumer trust in GMO crop regulations—agencies should make an effort to be clear with consumers, and consumers should make an effort to understand policies and procedures.

A Word From Verywell

In the case of GMOs, the scientific consensus is that they exhibit no toxicity and pose minimal risk (if any) to the environment. Every new GM product introduced will undergo its own analysis and careful testing, but to date, it appears that GMOs are nutritionally equivalent to their conventional counterparts. If you’re concerned about GMOs and your consumption of them, try using scientific journals and peer-reviewed information to make the best choices for you.

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