Levels of the chemical, called acrylamide, vary widely not only from food to food but between potato chip packages from the same snack brand or french fries bought at different branches of the same restaurant chain. Cooking time and temperature also seem to increase the accumulation of acrylamide in foods.
Acrylamide, an artifact of cooking, is present in everything from meats to vegetables, as well as in substances such as cigarette smoke. Until this year, scientists believed that smoking was the principal source of acrylamide exposure.
Concerns over acrylamide in the food supply were stoked in April by a report from Swedish scientists who discovered high amounts of the substance in certain fried and baked dishes. A few months later, a panel for the World Health Organization and the United Nations called the presence of the chemical in food a "serious problem" that warranted further study. The group stopped short of advising people to reduce their intake of things like bread, potato chips, and other foods heavy in acrylamide.
The FDA today released acrylamide levels from a preliminary list of scores of foods at a two-day meeting of its food advisory committee. The agency plans to test hundreds more products, come up with ways to reduce acrylamide in the food supply, and determine the true risk it poses to people.
"These sample results cannot and should not be generalized or used to reach conclusions about acrylamide levels in particular brands of foods," the agency said. "These samples are also not statistically representative of specific foods or brands."
Officials sampled 25 bags of Lay's Classic potato chips, and found almost no consistency in acrylamide content. When they went to Popeyes to test fries, they saw as much as a threefold difference in readings depending on the restaurant. At seven McDonald's outlets the gap was almost as great.
Toasting boosted acrylamide levels in bread products, but the effect varied significantly between items. Unbrewed coffee could have as much of the stuff as an order of french fries, but again the amount differed sharply from brand to brand.
Baby foods and infant formulas typically had low or undetectable levels of the chemical, officials said.
The reason for the wide variability of acrylamide may be an amino acid called asparagine, which is a precursor to the potential carcinogen. Concentrations of this molecule differ from food to food and between foods of the same type -- explaining why samples from a single batch of french fries or potato chips might yield different readings of acrylamide.
Jeff Nedelman, a spokesman for the Snack Food Association, said the FDA report raised many important questions yet offered few answers. "We don't know how much of acrylamide people normally eat per day and how quickly the acrylamide passes through the body. Those are the two key toxicological questions that FDA and the food industry are working on," Nedelman said.
For now, he said, there's nothing to say to consumers about what, if anything, they should do with the new information. "We're about a year from there, I would think."
Michael Pariza, director of the food research institute at the University of Wisconsin-Madison, said acrylamide is a weak carcinogen at worst. "I would say the health risk from acrylamide is pretty darn low," said Pariza, whose group has been studying the chemical. "You can't say it's zero but in some cases it is probably close to it."
For some diners, the potential harm from salty, fatty, and high-calorie foods will far outweigh the theoretical risk from eating acrylamide, Pariza added.
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