GMOs, short for genetically modified organisms, are subject to a lot of controversy.

According to the U.S. Department of Agriculture (USDA), GMO seeds are used to plant over 90% of all maize (corn), cotton, and soy grown in the United States, which means that many of the foods you eat likely contain GMOs (1).

Although most notable organizations and research suggest that GMO foods are safe and sustainable, some people claim they may harm your health and the environment.

This article helps explain what GMOs are, provides a balanced explanation of their pros and cons, and gives guidance on how to identify GMO foods.

What are GMOs?

“GMO,” which stands for genetically modified organism, refers to any organism whose DNA has been modified using genetic engineering technology.

In the food industry, GMO crops have had genes added to them for various reasons, such as improving their growth, nutritional content, sustainability, pest resistance, and ease of farming (2).

While it’s possible to naturally give foods desirable traits through selective breeding, this process takes many generations. Also, breeders may struggle to determine which genetic change has led to a new trait.

Genetic modification significantly accelerates this process by using scientific techniques that give the plant the specific desired trait.

For example, one of the most common GMO crops is Bt corn, which is genetically modified to produce the insecticide Bt toxin. By making this toxin, the corn is able to resist pests, reducing the need for pesticides (3).

GMO crops are incredibly common in the United States, with at least 90% of soy, cotton, and corn being grown through genetic techniques (4).

In fact, it’s estimated that up to 80% of foods in supermarkets contain ingredients that come from genetically modified crops.

While GMO crops make farming much easier, there is some concern around their potential effect on the environment and their safety for human consumption — specifically surrounding illnesses and allergies (5).

However, the Food and Drug Administration (FDA), Environmental Protection Agency (EPA), and USDA maintain that GMOs are safe for human and animal consumption (6).

Summary

GMOs are food items that have been made using genetic engineering techniques. They comprise 90% of soy, cotton, and corn grown in the United States and are deemed safe for human consumption.

Advantages of GMO foods

GMO foods may offer several advantages to the grower and consumer.

For starters, many GMO crops have been genetically modified to express a gene that protects them against pests and insects.

For example, the Bt gene is commonly genetically engineered into crops like corn, cotton, and soybeans. It comes from a naturally occurring bacteria known as Bacillus thuringiensis.

This gene produces a protein that is toxic to several pests and insects, which gives the GMO plants a natural resistance. As such, the GMO crops don’t need to be exposed to harmful pesticides as often (7).

In fact, an analysis of 147 studies from 2014 found that GMO technology has reduced chemical pesticide use by 37% and increased crop yields by 22% (8).

Other GMO crops have been modified with genes that help them survive stressful conditions, such as droughts, and resist diseases like blights, resulting in a higher yield for farmers (9, 10, 11).

Together, these factors help lower the costs for the farmers and consumers because it allows a greater crop yield and growth through harsher conditions.

Additionally, genetic modification can increase the nutritional value of foods. For example, rice high in beta carotene, also called golden rice, was developed to help prevent blindness in regions where local diets are chronically deficient in vitamin A (12).

Moreover, genetic modification may be used simply to enhance the flavor and appearance of foods, such as the non-browning apple (13).

In addition, current research suggests that GMO foods are safe for consumption (14).

Summary

GMO foods are easier and less costly for farmers to grow, which makes them cheaper for the consumer. GMO techniques may also enhance foods’ nutrients, flavor, and appearance.

Safety and concerns

Although current research suggests that GMO foods are safe, there is some concern around their long-term safety and environmental impact (14).

Here are some of the key concerns around GMO consumption.

Allergies

There is some concern that GMO foods may trigger an allergic reaction.

This is because GMO foods contain foreign genes, so some people worry that they harbor genes from foods that may prompt an allergic reaction.

A study from the mid-1990s found that adding a protein from Brazil nuts to GMO soybeans could trigger an allergic reaction in people sensitive to Brazil nuts. However, after scientists discovered this, they quickly abandoned this GMO food (15).

Although allergy concerns are valid, there have been no reports of allergic reactions to GMO foods currently on the market.

According to the FDA, researchers who develop GMO foods run tests to ensure that allergens aren’t transferred from one food to another (16).

In addition, research has shown that GMO foods are no likelier to trigger allergies than their non-GMO counterparts (17).

Yet, if you have a soy allergy, both GMO and non-GMO soy products will prompt an allergic reaction.

Cancers

Similarly, there’s a common concern that GMO foods may aid the progression of cancers.

Because cancers are caused by DNA mutations, some people fear that eating foods with added genes may affect your DNA.

This worry may stem partly from an early mice study, which linked GMO intake to a higher risk of tumors and early death. However, this study was later retracted because it was poorly designed (18, 19, 20).

Currently, no human research ties GMO intake to cancers.

The American Cancer Society (ACS) has stated that there’s no evidence to link GMO food intake to an increased or decreased risk of cancer (21).

All the same, no long-term human studies exist. Thus, more long-term human research is needed.

Other environmental and health concerns

Although GMO crops are convenient for farmers, there are environmental concerns.

Most GMO crops are resistant to herbicides, such as Roundup. This means that farmers can use Roundup without fear of it harming their own crops.

However, a growing number of weeds have developed resistance to this herbicide over time. This has led to even more Roundup being sprayed on crops to kill the resistant weeds because they can affect the crop harvest (22, 23, 24).

Roundup and its active ingredient glyphosate are subject to controversy because animal and test-tube studies have linked them to various diseases (25, 26, 27).

Still, a review of multiple studies concluded that the low amounts of glyphosate present on GMO foods are safe for human consumption (28).

GMO crops also allow for fewer pesticide applications, which is a positive for the environment.

That said, more long-term human research is necessary.

Summary

The main concerns around GMOs involve allergies, cancer, and environmental issues — all of which may affect the consumer. While current research suggests few risks, more long-term research is needed.

How to identify GMO foods

Although GMO foods appear safe for consumption, some people wish to avoid them. Still, this is difficult since most foods in your supermarket are made with ingredients from GMO crops.

GMO crops grown and sold in the United States include corn, soybean, canola, sugar beet, alfalfa, cotton, potatoes, papaya, summer squash, and a few apple varieties (29).

In the United States, no regulations currently mandate the labeling of GMO foods.

Yet, as of January 2022, the USDA will require food manufacturers to label all foods containing GMO ingredients (6).

That said, the labels won’t say “GMO” but instead the term “bioengineered food.” It will display either as the USDA bioengineered food symbol, listed on or near the ingredients, or as a scannable code on the package with directions, such as “Scan here for more information” (6).

Presently, some foods may have a third-party “Non-GMO project verified” label, which indicates that the product contains no GMOs. However, this label is voluntary.

It’s also worth noting that any food labeled “100% organic” does not contain any GMO ingredients, because U.S. law prohibits this. However, if a product is simply labeled “organic,” it may contain some GMOs (30).

In the European Union (EU), foods with more than 0.9% GMO ingredients must list “genetically modified” or “produced from genetically modified [name of food].” For foods without packaging, these words must be listed near the item, such as on the supermarket shelf (31).

Until the new regulations come into place in the United States, there is no clear way to tell if a food contains GMO ingredients.

However, you can try to avoid GMO foods by eating locally, as many small farms are unlikely to use GMO seeds. Alternatively, you can avoid foods that contain ingredients from the GMO crops listed above.

Summary

Until the 2022 USDA rule takes effect, it’s hard to determine which foods contain GMOs in the United States. You can avoid GMOs by limiting GMO ingredients, eating locally, looking for third-party non-GMO labels, or buying 100% organic.

The bottom line

GMOs are foods that have been modified using genetic techniques.

Most foods in your local supermarket contain GMO ingredients because they’re easier and more cost-effective for farmers, which makes them cheaper for the consumer.

In the United States, foods grown using GMO techniques include corn, soybean, canola, sugar beet, alfalfa, cotton, potatoes, papaya, summer squash, and a few varieties of apples.

Although current research suggests that GMO foods are safe for consumption, some people are concerned about their potential health effects. Due to a lack of long-term human studies, more research is needed.

In the United States, it’s currently not mandatory to label foods that contain GMOs. However, as of 2022, all foods that contain GMO ingredients must have the term “bioengineered food” somewhere on the packaging or a scannable code to show that it has GMO ingredients.