Diet and Colon Cancer Studies

By George Grow

This is Bill White with the VOA Special English SCIENCE REPORT.

Two new studies have disputed the idea that eating lots of fruits and vegetables can protect a person from colon cancer. The studies found that a diet low in fat and high in vegetable fiber did not prevent the formation of polyps in the colon, part of the large intestine. Polyps are small growths of tissue that sometimes can become cancerous.

Colon cancer is the fourth most common form of cancer in the world. Colon cancer is found mostly in industrial countries. It kills between five and eight times as many people in industrial countries as it does in developing nations.

Earlier studies have shown that the risk of colon cancer is lowest in people who eat low-fat, high-fiber foods including grains, fruits and vegetables.

The two new studies attempted to show if such a diet could prevent the growth of polyps. The studies involved more than three-thousand people who had polyps removed from their colons.

In one study, researchers at the University of Arizona compared people who ate a lot of grain or cereal fiber with a group who did not. The National Cancer Institute supervised the other study. It compared people who ate a lot of fruits and vegetables with those who did not. After four years, the researchers found that the people who ate the high-fiber diets developed just as many new polyps as the other people. The results of the studies were reported in the New England Journal of Medicine.

Arthur Schatzkin of the National Cancer Institute led the second study. That study is continuing with the same groups of people for five more years. Some doctors say the study may have been too short to measure the effects of a high-fiber diet. They say it takes up to fifteen years for polyps to grow large and develop into colon cancer.

Earlier studies have failed to show that changes in diet restrict the development of polyps. These studies involved Vitamins C and E, and beta carotene -- a substance found naturally in vegetables.

However, Doctor Schatzkin and other researchers say there are other reasons to eat low-fat foods with extra fiber from grains, fruits and vegetables. Such a diet has been shown to help fight weight problems, heart disease and diabetes.

This VOA Special English SCIENCE REPORT was written by George Grow. This is Bill White.