That the $100-billion fast food industry rests on a foundation of corn has been known more through inference and observation than hard scientific fact — until now.

Chemical analysis from restaurants across the United States shows that nearly every cow or chicken used in fast food is raised on a diet of corn, prompting fresh criticism of the government's role in subsidizing poor eating habits.

"People had talked about what they observed or found out about, as individual journalists or individual consumers," said University of Hawaii geobiologist and study co-author A. Hope Jahren. But anecdotes do not add up to scientific proof, she said. "We got national data on how this food is being produced. It's very objective."

Corn is central to agriculture in the United States, where it is grown in greater volumes and receives more government subsidies than any other crop. Between 1995 and 2006 corn growers received $56 billion in federal subsidies, and the annual figure may soon hit $10 billion.

But in recent years, environmentalists have branded corn as an icon of unsustainable agriculture. It requires large amounts of fertilizer and pesticides, both of which require large amounts of fossil fuel to manufacture.

Most of the resulting corn is fed to livestock who didn't evolve to subsist entirely on corn. In cattle, eating corn increases flatulence emissions of methane — a potent greenhouse gas — and creates an intestinal environment rich in *e. coli, *a common cause of food poisoning. That necessitates mixing cow feed with antibiotics, in turn producing antibiotic-resistant disease strains.

Many of those livestock end up in high-calorie, low-nutrition franchised fast foods, which have been repeatedly linked to obesity, diabetes and heart disease. Fast food's biggest selling point is its low price — and that, say industry critics, is largely possible because of corn's ubiquitous cheapness.

"We're seeing that corn is the number-one reason that fast food is so cheap and available," said Meredith Niles, a food policy analyst at the Center for Food Safety who was not involved in the study. "U.S. programs are subsidizing obesity in this country."

Jahren's team analyzed hamburgers, chicken sandwiches and french fries from multiple McDonald's, Burger King and Wendy's restaurants in six U.S. cities.

In both types of meat at every location, a telltale configuration of nitrogen and carbon traces showed that the animals had eaten corn-heavy diets; in the case of beef, 150 out of 162 samples came from animals that ate nothing but corn. Fries were prepared in corn-based oil.

The results weren't surprising, said New York University food studies expert Marion Nestle, but underscored the fact that "most people aren't aware of the extent to which corn ingredients permeate the food supply."

Nutrition aside, Jahren urged consumers to consider the implications of what they eat. "When you give a nickel to fast food, invariably it goes right back to the corn industry," she said.

For Niles, the results are a political challenge.

"We have a new President taking his place in the White House. It's a great opportunity to rearrange agricultural policy and to think about obesity," she said. "This study shows that it comes down in a lot of ways to one product."

Carbon and nitrogen stable isotopes in fast food: Signatures of corn and confinement* [PNAS]*

Image: Don

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