The Scientist

German scientists recently published a study implying that levels of the carcinogen acrylamide in the body might not be as strongly influenced by consumption of acrylamide-containing food as widely believed, sparking heavy criticism from their peers.

Fried and baked foods such as french fries and potato chips often contain high levels of acrylamide, a reagent biochemists use to separate proteins, and a neurotoxin and suspected carcinogen. Since acrylamide was detected in fried and baked goods, it has become a contentious issue among scientists, with bitter disagreements about its origin in humans and its potential dangers to health.

In the September 30 issue of the peer-reviewed medical journal Deutsches Ärzteblatt, researchers from the Medical School of Hannover in Germany examined the association between hemoglobin adducts of acrylamide and the diet and smoking habits of 395 people. "No association was found between acrylamide adduct concentration and diet," they wrote.

Study co-author Michael Bader, a chemist, told The Scientist that participants completed questionnaires asking how often during the previous 120 days they had smoked cigarettes and consumed acrylamide-rich foods -- such as French fries, chips, fried potatoes, crackers, cookies, coffee, and fatty meats such as bacon, schnitzel and bratwurst.

Some 80 percent of participants carried acrylamide adducts in their blood, with levels only slightly higher in non-smokers who ate acrylamide-rich foods more than once a week. A trend towards higher adduct concentration in heavy eaters of acrylamide did not reach statistical significance. However, the 99 cigarette smokers included in the study carried, on average, 1.5 micrograms per liter of blood, compared to 0.4 micrograms for non-smokers. Bader said this confirmed previous studies indicating that the human body retains a high level of acrylamide introduced by tobacco smoke. He and his colleagues suggest that a third source of acrylamide may help explain why some people carry more acrylamide in their bodies than others. For example, cosmetics, drinking water, or passive cigarette smoke can contain acrylamide.

"I think the conclusions are not valid," acrylamide expert Jürgen Angerer of the University of Erlangen-Nuremberg in Germany told The Scientist, adding that his main complaint is the questionnaire. "It is completely impossible to remember what you have eaten during the past 120 days." A prospective food diary that included portion sizes would have been more accurate, he noted.

Angerer added he is also highly skeptical of the study's assertion of a possible third source of acrylamide – in addition to food and smoking – in the human body. The study also came up at a recent conference of the International Society of Environmental Medicine held in Erlangen, Angerer said. "No one supported the conclusions."

In a news story in the dailyBerliner Zeitung, an anonymous source from Germany's Institute for Risk Assessment (BfR) complained that the study lacked a high enough sample number of heavy eaters – more than once a week – of acrylamide containing products. Bader conceded that of the 395 study participants, only 9 said they ate fried potatoes more than once week, 8 people chips more than once a week, and 3 people fries more than once a week.

Irene Lukassowitz, head spokeswoman for the Institute for Risk Assessment (BfR), declined to allow The Scientist to interview a BfR acrylamide expert about the Hanover study. However, she said the study had been noted within the BfR, which believes acrylamide in food is a health hazard to humans. "The study has not changed our view on acrylamide," she said.

Study co-author Bader told The Scientist the study had been peer-reviewed by two scientists when first submitted in December of 2004. The research team then addressed a long list of questions from the peer reviewers before publication. Bader said the team is now translating the study into English, and plans to submit it to an international journal.