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Fiber Facts - Does Fiber Decrease The Risk of Colon Cancer?
Still High on Fiber
Center for Colon and Rectal Surgery
Advice from TIME health columnist Christine Gorman

It's enough to make you reach for a bowl of ice cream. For years researchers have said that maintaining a diet that's high in fiber--found in fruits, vegetables and whole grains--should lower your risk of developing colon cancer. Now comes word that a study of nearly 89,000 women, published in last week's New England Journal of Medicine, has found that fiber makes no difference. A smaller 1997 study of men arrived at a similar conclusion. This is the sort of neck-snapping nutritional news that drives consumers crazy. First something is good for you, then it's not. Who knows what it will be next week?

Well, here's my advice: Don't trade your oat bran for fried onion rings just yet. There are lots of other reasons, backed by solid research, to eat plenty of fiber. Study after study shows that fiber lowers blood pressure and cholesterol levels, as well as your chances of developing adult-onset diabetes. And even if it turns out that fiber doesn't prevent colon cancer, it does help maintain your intestinal health in other ways. Folks who eat lots of fruit and vegetables don't usually develop diverticulitis, an often painful inflammation of the intestinal wall.

What made anyone think fiber could prevent colon cancer in the first place? It all started 30 years ago, when a British medical missionary named Denis Burkitt suggested that the reason colon cancer is rare in Africa is that Africans consume much more fiber than North Americans and Europeans. Perhaps, later researchers argued, the extra fiber sweeps the bowel clean of potential carcinogens or somehow alters the intestinal chemistry to retard tumor growth. A few small studies supported the link, while others didn't.

Enter the Nurses' Health Study, an ongoing analysis of the health and nutritional habits of more than 120,000 female registered nurses that began in 1976. Last October, researchers from the Brigham and Women's Hospital in Boston used the data to determine that women who consumed daily at least 400 micrograms of folic acid--one of the B vitamins--decreased their risk of colon cancer as much as 75% over 15 years. Intriguingly, folic acid, which is generally consumed in the form of folate, is commonly found in many fruits and vegetables. But it didn't matter whether the women got their folic acid from food or dietary supplements.

When the Brigham researchers looked at fiber intake alone, however, a different picture emerged. After excluding women who had already developed colon cancer or had other factors that might skew the data, the researchers found 787 cases of colorectal cancer from 1980 to 1996 among 88,757 women. Yet the nurses who consumed the most fiber (around 25 g a day) were no better off than the ones who ate the least (10 g a day). There was an indication that "fiber from fruit might protect against colon cancer," says Dr. Charles Fuchs, a gastrointestinal oncologist who led the study. "But the data weren't statistically significant."

So what should you do if you're worried about colon cancer? Current evidence suggests that you take a multivitamin that contains 400 micrograms of folic acid, don't smoke, avoid eating red meat more than five times a week and get plenty of exercise. Whatever you do, don't use the Nurses' Health Study as an excuse to skimp on fruits and vegetables. The rest of your body might never forgive you.