Folate as a possible hedge against colon cancer

You've probably heard that the B vitamin folate helps ward off birth defects as well as heart disease. An accumulating body of research now suggests that it also might be able to stave off colon cancer, the second leading cancer killer in this country. A few years ago, researchers at Tufts and the University of Toronto conducted a study in which they measured the amount of folate in the tissue that lines the interior of people's colons (as opposed to simply looking at the levels of folate in the blood). All of the subjects were already undergoing a medical procedure to remove adenomas--polyps in the colon that have the potential to turn into cancerous tumors.

What the researchers found was that those people whose polyps did in fact turn out to be precancerous had 34 percent less folate in their colon walls than those whose polyps turned out to be benign.

The results do not prove that eating a high-folate diet will stave off colon cancer. It's possible, says Tufts scientist Joel Mason, MD, that people who develop colon cancer consume just as much folate as others but that as the disease develops over time, folate stores somehow become depleted.

That's why Dr. Mason, who directs the Vitamins and Carcinogenesis Program at Tufts, went on to design a second study. This time, in a multi-center trial, subjects are being given either 1,000 micrograms of folate a day (2 1/2 times the Daily Value) or a placebo to see if there's a cause-and-effect relationship between folate and colon cancer prevention. The study is still in progress, and it is double-blinded, meaning that neither the researchers nor the subjects know who is getting folate and who is getting the "dummy" pill. Thus, even Dr. Mason doesn't know the interim results.

But he does say that prior to this large research effort, he conducted a small, 5-year pilot trial at Tufts along the same lines, with all of the subjects having confirmed precancerous colon polyps. At the end of it, abnormalities in DNA that could predict the development of colon cancer were correcting themselves more quickly in the folate takers than in the placebo takers. But Dr. Mason cautions that the effect was "relatively modest" and that the study was a small one--too small to draw any public health recommendations.

When the results of his study come in--along with the results of similar studies being conducted at Harvard, Dartmouth, and Veterans Administration hospitals--we should be in a much better position to know if taking folate supplements (or multivitamins with folate) is a good idea for keeping colon cancer at bay.

To hedge their bets for now, Dr. Mason advises that people should eat plenty of green leafy vegetables, which are among the richest sources of folate in the American diet. In fact, he says, "a diet that is rich in fruits and vegetables and low in beef, pork, and lamb seems to convey a protective effect." The produce also contains fiber, and even though recent studies suggest that fiber doesn't offer a preventive benefit, he comments that "my recommendation to patients is still to consume a high-fiber diet as a cancer-prevention measure."

Other ways to ward off colon cancer, according to Dr. Mason: Get regular exercise and keep alcohol consumption moderate. "Both seem to be independent predictors of risk," he says. Calcium looks protective as well, he notes.

Dr. Mason adds that "screening continues to be a very important component for colon cancer prevention, particularly for people at high risk--those with polyps or who have first-degree relatives with the disease." That means getting the test for hidden blood in the stools once a year, a sigmoidoscopy every 5 years, or, preferably, a colonoscopy every 10 years once you're in your 50s. If you're over 50 and your doctor hasn't brought these tests up to you, bring them up to him or her. Colon cancer is one of the few cancers that can be prevented rather than simply detected, since polyps can be removed before they become cancerous.

PHOTO (BLACK & WHITE): Joel Mason, MD, Director, Vitamins and Carcinogenesis Program

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By Joel Mason, MD, Director, Vitamins and Carcinogenesis Program

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