Most Fast-Food French Fries Cooked in Unhealthiest Oil

Jan. 19 -- MONDAY, Jan. 18 (HealthDay News) -- Most French fries served in U.S. restaurants are immersed in corn-based oil -- usually considered the worst oil for human health -- before they're fried, according to the authors of a new study.

Corn oil contains copious amounts of saturated fat, known to contribute to heart disease.

This type of oil is also low in monounsaturated fat, which most Americans need more of, and high in polyunsaturated fat, which, in too-large quantities, can lower HDL ("good") cholesterol along with LDL ("bad") cholesterol, said Karen Congro, a registered dietician and director of the Wellness for Life Program at The Brooklyn Hospital Center in New York City.

Congro was not involved with the new study, published online this week in the Proceedings of the National Academy of Sciences.

The same research group that performed this study reported in November that corn, which has been linked to obesity, is a prime ingredient in almost all fast-food sold in the United States, either directly or through animal feed.

Chain restaurants are not required to provide "specific" information on ingredients in the food they offer, while small businesses do not have to provide any information at all.

"Restaurants don't tell you what they're using and, even if you ask them, they will be very cagey," Congro said. "It will be a blend, but the blend is never a blend of anything you want to use."

French fries are particularly worthy of study, said the authors, from the University of Hawaii-Manoa, because they contribute 20 percent of the calories from a fast-food meal via the fat in the frying vat.

And Americans get about one-third of their total calories from restaurants.

The authors focused their attention on the saturated fat content of corn oil, which is higher than in canola, sunflower or safflower oils.

The researchers bought French fries from 68 of the 101 national fast-food restaurants represented on the island of Oahu, including McDonald's, Wendy's, Burger King and others, as well as from 66 small businesses. Then they measured carbon isotope composition of the oil used to fry the food.