Too much corn is bad for you—and it’s in nearly everything we eat

While most of us are encouraged to “eat more fruits and vegetables,” we probably don’t realize just how much one vegetable has become part of our daily diet. People in the United States eat more than 672 billion pounds of corn per year, which breaks down to more than 2,000 pounds per person annually. 

Eating the whole form of the vegetable—which is also considered a grain—at a summer barbecue, as popcorn, or as corn flour has undisputed health benefits such as lowering one’s risk of cancer, stroke, and heart disease. But most of us are consuming less whole corn and far more processed corn in the form of corn oil, corn starch, cornmeal, and high fructose corn syrup—which can contribute to adverse health outcomes including high blood pressure and high blood sugar, plus increased risk of obesity, fatty liver disease, colorectal cancer, and type 2 diabetes.

“Our main concern about corn should be the way it is being used because corn is at the center of a dysfunctional food system that fuels climate change and undermines human health,” says Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health. 

Neha Pathak, chair of the American College of Lifestyle Medicine in Missouri and a physician and editor at WebMD, agrees. “As a staple ingredient in various processed foods and animal feed, corn has had a massive impact on diets in the United States and across the globe,” she says. “Subsidizing corn has significantly influenced American and global food systems, promoting diets high in processed foods and animal fat, and low in fiber and nutritional diversity.”  

Indeed, most of us are unaware that we are consuming corn derivatives in countless unsuspected food sources including salad dressing, biscuits and bread, catsup, baby foods, chewing gum, doughnuts, cheese spreads, ice cream, tortillas, crackers, candies, processed meat, mayonnaise, peanut butter, pancake mix, soup, chips, breakfast cereal, frozen seafood, syrup, marshmallows, canned fruit, and most soft drinks. 

(How ultra-processed food harms the body and brain)

“Excessive reliance on any single food can lead to imbalances in nutrient intake, potentially resulting in deficiencies or other health issues,” says Jen Messer, a registered dietitian and president of the New Hampshire Academy of Nutrition and Dietetics. “Corn’s widespread consumption raises questions about its cumulative effects on health.” 

Is processed corn bad for you? 

This is most evident in the byproducts of corn that have been shown to have negative health outcomes.

“The major issue with corn is that it is typically highly processed into substances that are inflammatory and metabolically unsafe,” says Neil Iyengar, an oncologist who studies the relationship between diet, metabolism, and cancer at the Memorial Sloan Kettering Cancer Center in New York City. As one example, he points to high fructose corn syrup, “which can promote cancer growth through metabolic dysregulation and inflammation.”

High fructose corn syrup also has been linked to “increased risks of obesity, heart disease, and type 2 diabetes,” says Jill Weisenberger, a Virginia-based registered dietician and author of “Prediabetes: A Complete Guide.” She adds that some studies suggest that high fructose corn syrup increases markers of inflammation even more than table sugar. This is one reason excessive consumption can also lead to fatty liver disease, says Pathak. 

High fructose corn syrup is also responsible for people eating more added sugars than is healthy. The average American consumes 17 teaspoons of added sugars daily—far more than  the nine teaspoons recommended daily by the American Heart Association for men or the six teaspoons recommended daily for women. 

“High fructose corn syrup makes up about 40 percent of our added sugars, so avoiding foods with it is one way to naturally lower added sugar intake,” says Alexis Supan, a registered dietitian and nutritionist with Cleveland Clinic in Ohio. 

This is critical because recent research shows that even a 5 percent increase in added sugar intake comes with a 6 percent higher risk of developing heart disease and a 10 percent higher risk of stroke.

While high fructose corn syrup is likely the most harmful corn derivative, other byproducts are also worrisome. 

Corn starch and cornmeal, for instance, are both refined so that key nutrients are removed and are each digested rapidly, leading to a rush of glucose into the bloodstream. This is why the glycemic index—a scale that measures how quickly a food raises blood sugar levels—of corn starch is higher even than that of table sugar, which has a glycemic index of 65. 

“Whole corn has a glycemic index of 52, but corn starch is a whopping 97,” says Dariush Mozaffarian, a cardiologist and the director of the Food is Medicine Institute at the Friedman School of Nutrition Science and Policy at Tufts University. 

Along with increasing one’s risk of developing chronic disease, he adds, “the rapid and complete digestion of foods made with corn starch leaves one feeling hungry and unhappy, with negative metabolic and inflammatory consequences.” 

Corn also accounts for more than 95 percent of the total feed grain used in the United States, which affects the composition of that animal’s flesh, says David Katz, a physician, nutrition specialist, and director of the Prevention Research Center at Yale University. This causes “the meat of corn-fed cattle to be different in undesirable ways from the meat of grass-fed, pasture-raised cattle,” he explains.

Indeed, corn-fed cattle have a higher fat content than grass-fed cattle, “and fattier meats contribute to more weight gain,” says Abbie McLellan, a clinical dietitian with Stanford Health Care. Corn-fed cattle also have less omega-3 fatty acids, which are important in preventing disease, improving eye health, and reducing risks related to dementia and cardiovascular disease.  

How corn became America’s top crop

Corn became America’s top crop due to a number of factors that started with the U.S. government wanting to help out struggling farmers during the Great Depression. That’s when, Pathak explains, the government introduced agricultural subsidies to stabilize prices, ensure farmers’ income, and secure the food supply. “Over time, these subsidies became heavily skewed towards commodity crops like corn, especially with the introduction of the Farm Bill of the 1970s—which emphasized maximizing production and eventually lead to an overproduction of corn,” she says. 

Indeed, corn production tripled from 4.2 billion bushels in 1970 to 14.2 billion bushels by 2020.

Beyond the financial incentives provided to farmers, “corn is well-matched with the soils and climate of U.S. heartland states such as Iowa and Illinois,” says Parke Wilde, an agricultural economist and professor at the Friedman School of Nutrition Science and Policy at Tufts University. 

The crop is also attractive to farmers because it provides “a higher yield of food per unit than any other grain,” says Vijaya Surampudi, a physician and clinical nutritionist at UCLA Health in California; and because it can be processed into multiple byproducts that each have their own income stream. 

“The germ can be used for corn oil, the bran and stalk can be used for animal feed, and the starchy endosperm can be used for corn starch, high fructose corn syrup, or ethanol to fuel cars and trucks,” says Willett.  

Altogether, corn has become “so integrated into our food supply that I suspect moving away from it would be very costly and difficult,” says McLellan.

Indeed, along with being vital in countless food products, corn has a host of industrial uses as well including in adhesives, batteries, insecticides, food packaging, gasoline, textiles, art supplies, soap, dyes and inks, flooring, book binding, wallpaper, drinking straws, cosmetics, explosives, tires, and leather tanning. It’s also used in metal, plastic, and paper production. 

“Even in non-food sources, exposure to some of these products can have long-term health impacts, including potential endocrine disruption and increased cancer risk,” says Pathak. 

Why is whole corn good for you? 

Though the aforementioned corn derivatives are the most worrisome, one byproduct of corn that should still be eaten in moderation but often gets a worse rap than it deserves is corn oil. While this type of vegetable oil is high in calories, “it’s still considered a healthy fat and will reduce blood LDL (bad) cholesterol,” says Willett. It’s also a good source of omega-6 fatty acids, “which are not inflammatory and are associated with good health,” says Weisenberger.

(The Mediterranean diet has stood the test of time for a reason: It works)

Unrefined corn flour is another byproduct of the vegetable that tends to have all the nutrients that whole-kernel corn contains. This is because corn flour is simply whole corn that’s been ground to a fine texture. “Since the bran, germ, and endosperm are all included in the final product, this is one of the healthiest corn products available,” says McLellan. 

But the best way to glean all the health benefits corn has to offer is to enjoy the whole form of the vegetable such as eating it off the cob or as whole kernels that have been popped, canned, or bagged and frozen. “Whole corn—which is produced conscientiously, without pesticides, and grown in living soil—is healthful,” says Ron Weiss, a double board-certified internal medicine and lifestyle medicine physician practicing in New Jersey. 

Indeed, according to the USDA, a single medium ear of corn contains more than 3 grams of protein, 2 grams of dietary fiber, 37 milligrams of magnesium, 90 milligrams of phosphorus, and a whopping 275 milligrams of potassium. The vegetable also contains iron, calcium, manganese, copper, zinc, vitamin A, several B vitamins such as B6, niacin, and folate, plus vitamin C, vitamin E, and phytonutrients including lutein and zeaxanthin—which support vision and brain health. 

Messer says that many of these whole corn-related nutrients are especially valuable because “they are often missing from the standard American diet.” Katz echoes that these nutrients can be obtained from other whole grains, “but since Americans don’t eat a lot of these, corn’s nutrient profile readily steps in to fill the void.” 

And while unprocessed corn is still high in starch, “the whole kernel acts like a time-release capsule that slows down the digestion of the starch and reduces the spike in blood glucose,” says Willett.

It’s another reason nutrition scientists don’t recommend avoiding corn altogether, but to instead minimize consumption of its processed and refined varieties, when possible. 

“While you don’t have to completely avoid processed foods, it’s important to balance their role in your diet,” advises Messer. “Knowledge is power when it comes to choosing the food you put on your plate.”

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