Does Diet Have a Role in Preventing Colon Cancer?

Source: Tufts University
June 8, 2000 (Reviewed: December 10, 2002)

Two studies published in this week's New England Journal of Medicine cast some doubt on whether the "right diet" can protect people from colon cancer.

The participants in both studies were men and women who had adenomas (polyps, or growths) removed from their colons (the lower part of the large intestine) in the months before the studies began. Both studies were designed to see if dietary changes could reduce the recurrence of adenomas, a potent risk factor for colon cancer.

In a four-year study sponsored by the National Cancer Institute, almost 2000 men and women consumed either their regular diet or a diet low in fat and high in fiber, fruits, and vegetables. In a similar three-year study conducted in Arizona, 1300 men and women consumed either their regular diet or a higher-fiber diet that included a wheat bran fiber supplement. In both cases, diet did not appear to make a difference--study participants who followed their regular diets were no more likely than those on the modified diets to suffer from recurring adenomas.

These findings are surprising because a diet low in fat and high in fiber-rich whole grains, fruits, and vegetables is frequently cited by health professionals as one change that everyone can make to reduce their risk of colon cancer.

Why didn't diet have an effect? The scientists who conducted the studies say that because cancer develops over a long period of time, these studies may have been too short to show positive results. Also, all of the study participants had had at least one polyp removed before the studies began. It is possible that dietary components, like the phytochemicals in fruits and vegetables, may keep normal intestinal cells healthy but are less effective once polyps have already formed.

Consumers who think that the information from these new studies means that "diet doesn't matter," though, should keep in mind that a low-fat, produce-rich diet is a prudent hedge against heart disease. And, while scientists are not sure what role dietary fiber plays in cancer prevention, scores of earlier studies suggest that a diet high in vegetables may, in fact, reduce the risk of colon cancer in some people.

The failure of diet in these studies to slow the formation of potentially cancerous polyps underscores the importance of screening techniques that can catch colon cancer in its earliest, most treatable stages. The American Cancer Society's Website posts more information on colon and rectum cancer prevention and risk factors.

Related Links
Food choices for reducing cancer risk American Dietetic Association
The importance of nutrition in cancer prevention American Cancer Society

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