WASHINGTON — Whether you’re eating burgers, chicken or fries at the nation’s top fast-food eateries, corn is what’s for dinner.
The vast majority of the cows and chickens served at McDonald’s, Burger King and Wendy’s were raised on corn, and sizzling corn oil cooked many of the fries, according to a new study in Tuesday’s issue of Proceedings of the National Academy of Sciences.
Hope Jahren of the University of Hawaii said her researchers purchased three burgers, three chicken sandwiches and three orders of fries at three restaurants from each of the chains in Los Angeles, San Francisco, Denver, Detroit, Boston and Baltimore.
The foods were then tested for stable isotopes of carbon and nitrogen that allow researchers to trace the type of fat used or the source of nutrition for the animals. Jahren, of the Department of Geology and Geophysics, is an expert on stable isotopes who researches analytical techniques.
Of course, fast-food companies do not raise livestock, but purchase it from other companies.
The paper noted that most of the meat is developed in the final weeks before slaughter and that is also the time when the ratio of isotopes is set.
Jahren’s study found that 100 percent of the sampled chicken had been fed a corn-based diet, as had most of the beef. Only 12 samples of beef — all from West Coast Burger Kings — indicated a food source in addition to corn.
For fries, Wendy’s samples showed a corn-based oil while Burger King and McDonald’s used other oils. Burger King’s Web site reports it fries in vegetable shortening, while McDonald’s says it uses a combination of oils.