Reporting in the New England Journal of Medicine, Harvard scientists found that women who had beef, lamb or pork as a daily main dish ran 2 1/2 times the risk of developing colon cancer as did those who ate the meats less than once a month. One surprise: eating dairy products, which also tend to be high in animal fats, did not appear to increase the disease risk. The conclusions are drawn from a study of 88,751 nurses that was begun in 1980. The women filled out diet and medical questionnaires and were resurveyed at intervals over the next six years; 150 of the nurses developed colon cancer. The researchers believe their findings apply to men as well, though confirmation awaits the results of a parallel study.
The American Cancer Society estimates that there will be 155,000 new cases of colon cancer this year and almost 61,000 deaths from the disease, making it second only to lung cancer among fatal malignancies. Diets high in fat and low in fiber from fruits and vegetables have long been implicated in the disease. One clue: the ailment becomes more common among people as they emigrate from countries, like Japan, where meat consumption is low, to the U.S., where meat is a staple. Scientists speculate that bile acids produced by the liver to help digest fats can damage the intestine. Another theory is that red meat may contain cancer-triggering chemicals.
The women in the study got about 37% of their daily calories from fat, the average for the general population these days. Federal dietary guidelines recommend reducing fat to no more than 30% of calories. In particular, people are urged to eat less red meat and more main courses lower in fat, such as chicken and fish. The merits of such a plan were borne out in the Harvard study: the more poultry and fish in the nurses' diet, the lower their chances of getting colon cancer. Women who consumed skinless chicken two or more times a week had half the risk of those who ate it less than once a month. "The less red meat the better," says Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health, who directed the study. "At most, it should be eaten only occasionally. And it may be maximally effective not to eat red meat at all."
To many, Willett's words sound like a call to vegetarianism. The meat industry, which has watched sales slip as health consciousness has climbed, was particularly incensed. Nutritionist David Hurt of the National Livestock and Meat Board points out that the study does not demonstrate cause and effect, and that cattle and pigs increasingly are being bred to produce less fatty meat. "Beef is 27% leaner than it was in 1986 and pork 31%," he observes.
More disinterested experts also object to proscribing meat. The picture on diet and colon cancer is still very murky, they contend. Moreover, small amounts of lean meat can be very nutritious. "Meat is the single richest source of iron and zinc and contributes significant amounts of vitamins," says Mary Abbott Hess, a registered dietitian and president of the American Dietetic Association. "Women consume relatively few calories compared with men. And eliminating meat means that they'll have a hard time getting those nutrients elsewhere." Dr. Peter Greenwald, director of cancer prevention and control at the National Cancer Institute, agrees: "It's a good and important study, but it's going beyond the data to recommend becoming a vegetarian." The word for now remains cut back, not cut out.