A landmark report released last week by the American Institute for Cancer Research and the World Cancer Research Fund found strong evidence linking excess body weight to the risk of developing cancer, and also linked the consumption of alcohol and red meat, particularly processed red meat, to higher risk for cancer.
Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective was the culmination of a five-year project — the most comprehensive ever published on the links between diet, physical activity and weight — in which nine independent teams of scientists from around the world, hundreds of peer reviewers, and 21 international experts analyzed more than 7,000 large-scale studies.
Specifically, the report found convincing evidence that excess body fat increases the risk for cancer of the esophagus, pancreas, colon, kidney, endometrium, and, for post-menopausal women, breast cancer. It found links between alcohol consumption and cancers of the mouth, pharynx, larynx, esophagus, and colorectal tract. The authors thus recommended that people be as lean as possible and limit alcoholic drinks. Other recommendations were to be physically active, limit consumption of sugary foods, eat mostly foods of plant origin, limit consumption of salt and to breastfeed.
"It basically states what nutritionists have been preaching all along," says Manfred Kroger, professor of food science at Penn State University, who called the report a "comprehensive piece of science."
The finding that has already sparked some controversy is evidence linking red meat — beef, pork and lamb — to colorectal cancer. The experts recommend consuming no more than 18 ounces of red meat per week, and that processed meat, including bacon, ham, sausage, and lunchmeat, be avoided altogether.
In response, David Martosko, research director at the Center for Consumer Freedom, released a statement objecting to the meat recommendations because the report was based on "unreliable epidemiological studies." He cites a clinical trial published in the Journal of Nutrition this month that found the U.S. Department of Agriculture's Food Guide diet, which includes lean red meat, reduced the risk of developing colon cancer by 26 percent. "We simply don't know enough about cancer prevention to justify the claim that one food or another is largely to blame," he said. "The science on meat and colon cancer risk is sketchy at best."
Kroger says the coming months should be met with lively debate on the meat recommendations, as meat interests will try to deflate the report's findings. "One argument might be that you will gain weight or even get obese by totally excluding meat products," he says. "In essence, the report tells people who now eat 4 pounds of red meat a week to scale it down to 1. The poultry and fish sellers must be delighted, and the pork people will increasingly insist that their product isn't red at all."
Carl Winter, director of the FoodSafe Program at University of California-Davis, says he hopes the message to eat less and exercise won't be lost as experts debate the report's specifics. "What I'm worried about when a report like this is disseminated is that consumers get the idea that there are red-light foods—processed meats—and green-light foods, such as nonstarchy fruits and vegetables, and I think we overreact in many cases, and the message needs to be moderation."