Genetically modified (GM) corn refers to corn that has undergone alterations to its deoxyribonucleic acid (DNA) through genetic engineering techniques. This process introduces new traits into the corn plant that are not naturally occurring or achievable through traditional breeding methods. These modifications aim to enhance specific characteristics of the crop.
The Purpose of Genetically Modifying Corn
Genetic modification in corn primarily focuses on introducing traits that improve agricultural efficiency and reduce reliance on certain farming practices. Two prominent traits engineered into commercial corn varieties are insect resistance and herbicide tolerance. These modifications address common challenges faced by farmers, contributing to crop protection and weed management.
One significant modification involves introducing a gene from the soil bacterium Bacillus thuringiensis (Bt) into the corn plant, creating Bt corn. This enables the corn to produce specific proteins that are toxic to certain insect pests, such as the European corn borer. When larvae ingest Bt corn, the protein activates in their digestive system, causing them to stop feeding and die within days. This internal defense reduces the need for external chemical insecticides throughout the growing season.
Another widely adopted modification confers herbicide tolerance to corn plants. Varieties are engineered to be resistant to specific broad-spectrum herbicides, such as glyphosate. Glyphosate works by inhibiting a plant enzyme called 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which is involved in producing essential amino acids. Genetically modified, herbicide-tolerant corn typically contains a bacterial gene that produces a version of the EPSPS enzyme unaffected by glyphosate. This allows farmers to spray herbicides to control weeds without harming the corn crop itself, simplifying weed management and often enabling conservation tillage practices.
Health and Environmental Safety Evaluation
The safety of genetically modified corn undergoes thorough assessment by multiple regulatory agencies in the United States. This oversight ensures comprehensive evaluation before GM corn is permitted for commercial use. The U.S. Food and Drug Administration (FDA) evaluates food safety for humans and animals, ensuring GM foods meet the same rigorous standards as conventional foods.
The U.S. Environmental Protection Agency (EPA) assesses the environmental impact of plant-incorporated protectants (PIPs), such as the Bt proteins in insect-resistant corn, regulating them as pesticides. This includes evaluating potential effects on non-target organisms. The U.S. Department of Agriculture (USDA) regulates GM plants to ensure they do not pose a risk as plant pests to other crops or the broader agricultural ecosystem.
A broad scientific consensus among major scientific and medical organizations worldwide indicates that currently available GM foods are as safe to consume as conventionally bred foods. This conclusion is based on thousands of scientific studies and regulatory reviews.
Environmental considerations are also part of the safety evaluation. One concern involves the potential for repeated use of glyphosate with herbicide-tolerant crops to lead to herbicide-resistant weeds, sometimes called “superweeds.”
Another environmental consideration involves the monarch butterfly. Early laboratory studies in 1999 raised concerns that pollen from Bt corn could harm monarch larvae. Subsequent field studies showed the actual risk to monarch populations from Bt corn pollen in real-world conditions is generally small due to low exposure levels. However, widespread adoption of herbicide-tolerant corn and soybeans has indirectly contributed to a decline in milkweed plants within agricultural fields, the sole food source for monarch caterpillars. This reduction in milkweed habitat impacts monarch populations.
Common Uses of GM Corn
Most genetically modified corn grown in the United States is not directly consumed by humans as fresh corn on the cob or whole kernels. Instead, it serves a variety of industrial and agricultural purposes. In 2020, approximately 92% of the corn planted in the U.S. was genetically modified.
The largest single use of GM corn is for animal feed, supporting livestock and poultry industries. Over 95% of animals raised for meat and dairy in the United States consume feeds that include GM corn.
A significant portion of GM corn is also directed towards ethanol production, serving as a primary feedstock for biofuel. Beyond animal feed and fuel, GM corn is processed into a wide array of ingredients found in numerous processed food products. Common examples include high-fructose corn syrup, corn starch, corn oil, and maltodextrin.
Labeling and Consumer Choice
The USDA’s National Bioengineered Food Disclosure Standard provides mandatory labeling requirements for foods containing genetically modified ingredients. This standard, effective January 1, 2022, requires manufacturers, importers, and retailers to disclose when a food is “bioengineered” (BE) or contains BE ingredients. Disclosure can appear as text, a specific symbol, a digital link (QR code), or a phone number.
The standard defines bioengineered foods as those containing detectable genetic material modified through laboratory techniques that could not be achieved through conventional breeding or found in nature. However, certain highly refined ingredients derived from bioengineered crops, such as corn oil or high-fructose corn syrup, may not require a BE label if the processing removes all detectable modified genetic material from the final product.
For consumers seeking to avoid GM ingredients, voluntary labels like the “Non-GMO Project Verified” seal are available. This third-party certification indicates a product meets specific standards for avoiding genetically modified organisms. These voluntary labels offer an additional choice for consumers.