Genetically modified corn is corn that has had its DNA altered in a laboratory to carry specific traits it wouldn’t develop through traditional breeding. These traits typically make the plant resistant to certain insects, tolerant of specific herbicides, or better able to survive drought. As of 2024, 94% of all corn planted in the United States is genetically modified, making it one of the most widely adopted biotech crops in the world.
How Corn Gets Modified
The most common type of genetic modification in corn involves borrowing a gene from a soil bacterium called Bacillus thuringiensis, or Bt for short. This bacterium naturally produces a protein that kills certain insect larvae when they eat it. Organic farmers have actually sprayed Bt bacteria on crops as a natural pesticide for decades. Genetic engineers took the gene responsible for producing that insect-killing protein and inserted it directly into the corn plant’s DNA, so the corn produces the protein on its own. When a pest like the European corn borer chews into a Bt corn plant, it ingests the protein and dies.
Herbicide tolerance works differently. Scientists insert a gene that allows the corn plant to survive exposure to a specific weed killer. Farmers can then spray their fields to eliminate weeds without damaging the crop. Most GM corn planted today actually carries both traits stacked together. USDA data from 2024 shows that 83% of U.S. corn acreage is planted with stacked varieties containing both insect resistance and herbicide tolerance. Only 3% carries Bt alone, and 7% carries herbicide tolerance alone.
Beyond Pest Control: Drought Tolerance
Not all genetic modifications are about fighting insects or weeds. One commercially available variety contains a gene from another soil bacterium, Bacillus subtilis, that produces a cold shock protein. This protein helps the corn plant maintain yields when water is limited. The grain and forage from this drought-tolerant variety have been shown to be compositionally equivalent to conventional corn, meaning the modification changes how the plant handles stress without altering what you’d find in the harvested crop.
Nutritional Differences
One of the most common questions about GM corn is whether it’s nutritionally different from conventional corn. The short answer: the differences are minimal and inconsistent. Comparative testing has found that non-GMO corn had slightly higher crude protein (8.03% vs. 7.86%), while GMO corn had slightly higher levels of certain amino acids like lysine and methionine, which are building blocks of protein. Crude fiber was higher in non-GMO corn (2.43% vs. 1.67%). These variations are small enough that they fall within the normal range you’d see between any two corn varieties grown under different conditions. From a practical nutrition standpoint, GM and conventional corn are essentially interchangeable.
How GM Corn Is Regulated
In the United States, three federal agencies share oversight of genetically modified crops. The FDA ensures that GM foods meet the same safety standards as all other foods sold for human and animal consumption. The EPA regulates the insect-killing proteins that Bt corn produces, treating them as “plant-incorporated protectants,” a category of pesticide built into the plant itself. The USDA’s Animal and Plant Health Inspection Service evaluates whether GM plants pose risks to other plants or agricultural systems.
Before any GM corn variety reaches the market, it goes through safety assessments that include allergenicity testing. Because many known food allergens share the trait of being resistant to digestion by stomach acid, regulators require testing to see whether the new proteins inserted into the corn break down quickly in simulated stomach conditions. Proteins are also tested for stability under heat, since cooking-resistant proteins are more likely to trigger allergic reactions. The Bt proteins used in most GM corn break down readily in digestion, which is one reason they’ve been cleared as safe for consumption.
How to Tell If Your Food Contains GM Corn
Given that 94% of U.S. corn is genetically modified, it’s in most processed foods that list corn-derived ingredients. High-fructose corn syrup, corn starch, corn oil, and dozens of other derivatives likely originate from GM corn unless specifically labeled otherwise.
Under the National Bioengineered Food Disclosure Standard, foods sold in the U.S. that contain bioengineered ingredients must carry a disclosure. This can appear as text reading “Contains a bioengineered food ingredient,” a specific symbol (a green circle with the letters “BE”), a QR code, or a text-message number. The disclosure must be prominently placed on the label near the manufacturer information or on the front of the package. If you’re looking for corn products made without genetic modification, look for the USDA Organic seal or a Non-GMO Project Verified label, both of which restrict or exclude bioengineered ingredients.
Common Uses of GM Corn
Most genetically modified corn doesn’t end up as corn on the cob at your dinner table. Sweet corn, the type you eat directly, represents a small fraction of total corn production. The vast majority of GM corn is field corn, a starchier variety used for animal feed, ethanol fuel production, and processed food ingredients. When it does enter the human food supply, it’s typically broken down into components: sweeteners, oils, starches, and additives that appear in everything from soft drinks to salad dressings to breakfast cereals.
Globally, the United States is by far the largest producer of GM corn, followed by Brazil and Argentina. The crop’s dominance in American agriculture means that avoiding it entirely requires deliberate effort, since corn derivatives are among the most common ingredients in packaged foods.