Meaty findings about colon cancer and diet.

Meaty findings about colon cancer and diet

A large-scale, prospective study offers strong support for the long-standing suspicion that people who regularly eat red meat increase their risk of colon cancer. The study also turned up several new dietary indluences -- most notably that eating chicken and fish may reduce a person's risk of colon cancer, which ranks as the second leading cause of cancer deaths in the United States.

Through detailed questionnaires administered every two years since 1976, researchers at Brigham and Women's Hospital in Boston have been tracking the health of 121,700 female registered nurses in 11 states. In the colon cancer study, they focused on the nearly 89,000 participants who answered at least 85 percent of the food-consumption questions on the 1980 survey and had no history of colon-cancer-predisposing conditions. After following the women through three more surveys, they identified 150 who went on to develop the cancer.

The researchers, led by Walter C. Willett, looked for risk trends by analyzing the survey data on 61 different foods. Calorie consumption, dairy fats, vegetable fats, calcium, carotene and vitamins A, C, D and E had little or no effect on colon cancer risk, they found. But women who reported eating at least 1.4 ounces of animal fat daily showed a dose-dependent increase in colon cancer risk, the team reports in the Dec. 13 NEW ENGLAND JOURNAL OF MEDICINE.

Red meat appeared to account almost entirely for the increase. Women who daily ate a main dish containing beef, pork or lamb faced 2.5 times the colon cancer risk of women who ate red meat less than once a month. Weekly servings of liver or processed meats such as bologna increased the risk by 50 to 100 percent compared with less frequent consumption. However, eating fish two to four times a week or eating skinless chicken daily reduced the risk by 25 and 50 percent, respectively. Red meat, chicken and fish differ in their ratios of unsaturated-to-saturated fat, notes Willett, who speculates that this may account for the observed risk differences.

Frequent consumption of fiber from fruits also appeared to lower colon cancer risk, the investigators found.

John Weisburger of the American Health Foundation in Valhalla, N.Y., says the risk posed by animal fats might have proved even greater if the Boston team had singled out cancers of the left colon. "Several key studies including those we conducted, demonstrated very clearly that the right side of the colon is not sensitive to dietary fat," he says.

Peter Greenwald of the National Cancer Institute in Bethesda, Md., describes the new study as "good" but questions the researchers' simple recommendation that people substitute more chicken and fish for red meat. "My view is that you have to pay more attention to cooking methods," he says. Greenwald argues that small portions of broiled, lean red meat may pose no more risk -- and perhaps even less -- than regular serving of fish or skinless chicken deep-fried in fat.