New research suggests that many fast-food meals contain corn. Researchers uncovered signs of corn in food items from Wendy's, McDonald's and Burger King that had nothing to do with corn whatsoever. Out of the hundreds of fast food servings offered worldwide, scientists could only identify 12 servings of food that could be traced back to something besides corn.

During the study 480 servings of hamburgers, chicken sandwiches and fries from McDonald’s, Burger King, and Wendy’s chains in Los Angeles, San Francisco, Denver, Detroit, Boston, and Baltimore were sampled. And they found 100 percent and 93 percent of the cows responsible for the hamburgers and chicken sandwiches were fed exclusively corn-based diets.

Experts say cows and chicken that eat only corn meals or other grains are likely to produce high proportions of omega-6 fatty acids that are not good for health. And according to the study, Americans spend more than $100 billion a year on fast food. The study authors decided to analyze the fast food on an atomic level to discover how corn is used in the production of fast food.

By analyzing the biochemical makeup of the food, the researchers found that virtually all of the cows and chickens used had lived on exclusively corn-based diets. As for fries, there was a bit more diversity: while Wendy's cooked them in corn oil to make theirs, McDonald's and Burger King fries used other vegetable oils.

"Our results highlighted the overwhelming importance of corn agriculture within virtually every aspect of fast-food manufacture," Jahren and Rebecca Kraft reported in a recent issue of the Proceedings of the National Academy of Sciences. Her researchers have tried for years to get information from fast-food corporations about how their food is made, what it contains, where it comes from and how animals are fed and treated, she said.