Corn is an important but dangerous food

While most of us are advised to “eat more fruits and vegetables,” we probably don’t realize the extent to which a particular vegetable has become part of our daily diet. And especially in a particular country.

Although Spain only consumes about 37 million tons of wheat, barley and corn annually (of which 28 million go to animal feed), the United States consumes more than 300 million tons of corn per year, which is equivalent to more than 900 kilograms per person and year.

Eating this vegetable (which is also considered a grain) at a summer barbecue in the form of popcorn or whole cornmeal has undeniable health benefits, such as a reduced risk of cancer, stroke, and heart disease. But most of us consume less whole corn and much more processed corn in the form of corn oil, cornstarch, corn flour, and high-fructose corn syrup, which can also contribute to adverse health effects such as high blood pressure and hyperglycemia, as well as an increased risk of obesity, fatty liver disease, colorectal cancer, and type 2 diabetes.

“Our primary concern about corn should be how it is used, because corn is at the center of a dysfunctional food system that is contributing to climate change and undermining human health,” says Walter Willett, a professor of epidemiology and nutrition at the Harvard T.C. Chan School of Public Health.

Neha Pathak, president of the American College of Lifestyle Medicine in Missouri, is a physician and editor of the journal WebMDyou agree. “As a major ingredient in a variety of processed foods and feeds, corn has had a huge impact on diets in the United States and around the world,” he says. “Corn subsidies have had a significant impact on U.S. and global food systems, promoting diets high in processed foods and animal fats and low in fiber and nutrient diversity.”

In fact, most of us are unaware that we consume corn derivatives in countless unexpected food sources such as salad dressings, crackers and breads, tomato sauce, baby food, chewing gum, donuts, cheese spreads, ice cream, tortillas, crackers, candy, processed meats, mayonnaise, peanut butter, pancake mix, soup, potato chips, breakfast cereals, frozen seafood, syrup, marshmallows, canned fruit, and most soft drinks.

“Over-reliance on one food can create imbalances in nutrient intake, which can lead to deficiencies or other health problems,” says Jen Messer, a registered dietitian and president of the New Hampshire Academy of Nutrition and Dietetics. “The widespread consumption of corn raises questions about its overall health effects.”

This is most evident with regard to corn by-products, which have been shown to have negative health effects.

“The main problem with corn is that it’s typically highly processed into substances that are inflammatory and metabolically unhealthy,” says Neil Iyengar, an oncologist who studies the relationship between diet, metabolism, and cancer at Memorial Sloan-Kettering Cancer Center in New York City. He cites high-fructose corn syrup as an example, “which can promote cancer growth through metabolic dysregulation and inflammation.”

High-fructose corn syrup has also been linked to “an increased risk of obesity, heart disease, and type 2 diabetes,” says Jill Weisenberger, a Virginia-based registered dietitian and author of Prediabetes: The Complete Guide. He adds that some studies show that high-fructose corn syrup increases markers of inflammation even more than table sugar. “This is one reason why overconsumption can also lead to fatty liver disease,” Pathak says.

“High-fructose corn syrup accounts for 40% of added sugar, so avoiding foods that contain it is a way to naturally reduce your added sugar intake,” says Alexis Supan, a registered dietitian and nutritionist at the Cleveland Clinic in Ohio.

This is important because recent research shows that even a 5 percent increase in added sugar intake leads to a 6 percent increase in the risk of heart disease and a 10 percent increase in the risk of stroke.”

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

For example, cornstarch and corn flour are refined in a way that removes key nutrients and are quickly digested, causing a surge of glucose into the bloodstream. That’s why the glycemic index (a scale that measures how quickly food raises blood sugar) of cornstarch is higher than even table sugar, which has a glycemic index of 65.

“Whole corn has a glycemic index of 52, while cornstarch has a glycemic index of 97,” says Dariush Mozaffarian, a cardiologist and director of the Food Science Institute at the Friedman School of Nutrition Science and Policy at the University of Massachusetts Amherst.

In addition to increasing the risk of developing chronic diseases, he adds, “the rapid and complete digestion of foods made with cornstarch leaves you feeling hungry and uncomfortable, with negative metabolic and inflammatory consequences.”

Corn also makes up more than 95 percent of the total feed grain used in the U.S., which affects the composition of corn meat, says David Katz, a physician, nutritionist, and director of the Yale University Prevention Research Center. That makes “meat from corn-fed cattle undesirably different from meat from grass-fed cattle,” he explains.

In fact, corn-fed cattle have higher fat content than grass-fed cattle, “and the fattier meat contributes to more weight gain,” says Abby MacLellan, a clinical nutritionist at Stanford Health Care. Corn-fed cattle also contain less omega-3 fatty acids, which are important for preventing disease, improving eye health, and reducing the risks associated with dementia and heart disease.

Corn became America’s leading crop thanks to a number of factors, starting with the U.S. government’s desire to help struggling farmers during the Great Depression. That’s when, Pathak explains, the government introduced agricultural subsidies to stabilize prices, guarantee farmers’ incomes, and ensure food supplies. “Over time, these subsidies shifted toward staple crops like corn, especially with the passage of the Farm Bill in the 1970s, which emphasized maximizing production and ultimately led to corn overproduction,” he says.

Beyond the financial incentives offered to farmers, “corn is well suited to the soils and climates of states like Iowa and Illinois,” says Park Wild, an agricultural economist and professor at the Friedman School of Food Science and Policy at Tufts University.

The crop is also attractive to farmers because it provides “a higher food yield per unit of output than any other grain,” says Vijaya Surampudi, a physician and clinical nutritionist at UCLA Health in California; and because it can be turned into a variety of byproducts, each with its own source of income.

“These microbes can be used to make corn oil; the bran and stalk for feed; and the endosperm to make corn starch, high-fructose corn syrup, or ethanol for cars and trucks,” Willett explains.

Overall, corn is “so integrated into our food supply that I suspect it would be very expensive and difficult to get rid of,” McLellan says.

In fact, corn not only plays a vital role in countless food products, but also has many industrial uses such as glue, batteries, insecticides, food packaging, gasoline, textiles, art materials, soap, dyes and inks, flooring, book binding, paper paint, straws, cosmetics, explosives, tires and leather tanning. It is also used in the production of metal, plastic and paper.

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

While the aforementioned corn derivatives are the most worrisome, there’s a corn byproduct that should be consumed in moderation but that often gets a worse rap than it deserves: corn oil. While this type of vegetable oil is high in calories, “it’s considered a healthy fat and has been shown to lower LDL (bad) cholesterol in the blood,” says Willett. It’s also a good source of omega-6 fatty acids, “which are non-inflammatory and promote good health,” says Weisenberger.

Unrefined cornmeal is another vegetable byproduct that typically contains all the nutrients found in whole grain corn. That’s because cornmeal is simply whole corn ground into a fine texture. “Because the final product includes the bran, germ, and endosperm, it’s one of the healthiest corn products,” says McLellan.

But the best way to reap all the health benefits of corn is to enjoy it in its whole form, such as on the cob or as shredded, canned, or bagged and frozen whole kernels. “Whole corn that’s responsibly produced, pesticide-free, and grown in living soil is good for you,” says Ron Weiss, a double-board-certified physician in internal medicine and lifestyle medicine who practices in New Jersey.

In fact, according to the USDA, one average ear 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 like B6, niacin, and folate, as well as vitamin C, vitamin E, and phytonutrients like lutein and zeaxanthin, which promote healthy vision and brain function.

Messer says many of these nutrients associated with whole corn are especially valuable because they are “often lacking in the standard American diet.” Katz reiterates that these nutrients can be obtained from other whole grains, “but since Americans don’t consume many of them, corn’s nutritional profile easily fills the gap.”

And while raw corn still contains plenty of starch, “the entire kernel acts as a time-release capsule that slows the digestion of the starch and reduces the spike in blood glucose,” says Willett.

This is another reason why nutritionists do not recommend avoiding corn entirely, but rather minimizing consumption of processed and refined varieties whenever possible.

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