Corn syrup is in just about everything we eat. How bad is it?

Few ingredients are included in as many foods as corn syrup. Though it comes in various forms, the high-fructose variety of corn syrup is in soft drinks, condiments, baked goods, fast food, breakfast cereals, canned foods, yogurts and countless varieties of candy. It's what gives such foods their sweetness and "is a very common ingredient because it is inexpensive and helps enhance food flavor and texture," says Lisa Young, PhD, RDN, an adjunct professor of nutrition at New York University and author of "Finally Full, Finally Slim." 

Corn syrup is also popular because it extends the shelf life of the products it's used in by controlling microbial growth. 

What is corn syrup?

Corn syrup is a liquid sweetener that is derived from cornstarch and contains varying amounts of glucose and fructose. The two main varieties of corn syrup are regular corn syrup and high fructose corn syrup. The regular variety is the one most people cook with at home, and it comes in both light and dark forms. "The light form has a vanilla flavor and a nearly clear color, and the dark form is a brown color and is a combination of corn syrup, inverted sugar syrup, caramel color, and a molasses flavor," explains Jen Messer, RD, a nutrition consultant and registered dietitian at Jen Messer Nutrition.

The high fructose variety of corn syrup is the one used in most packaged and processed foods and is similar to regular corn syrup, "but has undergone more processing than regular corn syrup to increase its fructose content," says Young. Indeed, the high-fructose variety isn’t all that different from sugar as table sugar consists of 50% fructose and 50% glucose, and high fructose corn syrup consists of 55% fructose and 42% glucose.

And while regular corn syrup has less fructose than high-fructose corn syrup, "one corn syrup is not 'healthier' than the other," cautions Messer. 

Is corn syrup bad for you?

Indeed, the U.S. Food and Drug Administration (FDA) notes that overconsumption of either variety of corn syrup can be harmful to health. Each variety has been linked to heart disease and type 2 diabetes, "and studies show that corn syrup increases appetite, thus promoting obesity," says Young. Obesity is associated with high blood pressure, high LDL cholesterol levels, heart attack, stroke and higher risk of early death.

Also contributing to potential weight gain is the fact that corn syrup contains a lot of sugar - 16 grams in a single tablespoon of regular corn syrup; and that it's also high in calories - 57 calories in one tablespoon of regular corn syrup. What's more, "any excess fructose in corn syrup that is not immediately used for energy or stored as glycogen can then be converted into fat storage," says Messer.

"There is also evidence to suggest that the excess fructose or sucrose (glucose + fructose) in high fructose corn syrup can have negative effects on the liver, increase triglycerides, and possibly increase risk of inflammatory-related conditions," adds Kate Zeratsky, RD, a registered dietitian nutritionist at Mayo Clinic in Rochester, MN. 

Is corn syrup OK in moderation? 

Because of such factors, it's important to limit the amount of corn syrup or high fructose corn syrup that's included in one's diet daily. The Dietary Guidelines for Americans recommends limiting all added sugars, including high fructose corn syrup, to no more than 50 grams a day. "This recommendation is fully supported by the FDA and all other health organizations," says Messer.

That means some added sugars in one's diet are OK -"it's the excess that is the problem," says Zeratsky. But consumers need to be aware of how fast added sugars add up. For instance, after carbonated water, the top ingredient in a can of Coca-Cola is high fructose corn syrup, and a single 12-ounce can has 39 grams of sugar - nearly 80% of what's recommended in an entire day. 

"It's a challenge that added sugars are in so many food products," says Messer, "which is why it's important to read food labels and identify items containing high levels of any added sugar, including high fructose corn syrup." The experts also recommend cutting down on candies and sodas and sticking to homemade baked goods instead of store-bought ones to limit overconsumption of high fructose corn syrup and other added sugars. 

"For most people, consuming corn syrup in small amounts as part of a well-balanced diet is generally considered safe," says Messer, "but keep in mind that your overall diet, lifestyle, and other factors play a significant role in determining health outcomes."