How to prevent colon cancer: new research updates old theories

Colon cancer is one of the most common cancers -- second only to lung cancer -- but it has no colorful ribbons to wear or celebrity bike-a-thons to spark the search for a cure. New York Yankee slugger Darryl Strawberry may change that. His diagnosis of colon cancer last fall, coming on the heels of the death from the disease of Jay Monahan, husband of Today show host Katie Couric, put colon cancer in the headlines.

In the months since, a flurry of news reports have honed in on early diagnosis as key to beating the disease. But colon cancer often provides no early warning signs. The real key to beating colon cancer is prevention. And the good news is that you may indeed be able to prevent colon cancer -- or at least improve your odds -- by making the right lifestyle choices. Not smoking, watching your weight, exercising and eating right are all pieces to the prevention puzzle. In fact, it's been estimated that up to 90% of colon cancers may be linked to dietary and lifestyle factors.

Focus Fading on Fiber? For 25 years, study after study has linked diets low in fiber to colon cancer. A recent consensus statement issued by the American Health Foundation reflects that widely accepted theory. It asserts that colon cancer could be largely prevented if people would simply include more fiber in their diets.

Most experts suggest aiming for at least 25 grams of fiber a day. The average American gets only about 15. The fiber deemed best for helping prevent colon cancer is insoluble fiber, found primarily in whole grain breads and cereals (look for 100% whole wheat), wheat bran and vegetables.

However, not everyone is convinced it's the fiber in fiber-rich foods that protects the colon. Edward Giovannucci, M.D., Sc.D., of Harvard Medical School, for one: "It's an interesting theory," he says, "but I wouldn't characterize the evidence as firm."

Others agree. "The strongest dietary protector for colon cancer is vegetables," says Martha Slattery, Ph.D., M.P.H., of the University of Utah Medical Center in Salt Lake City. Vegetables as well as whole grains contain beneficial phytochemicals that may be as important, or more important, than fiber. Either way, you can't go wrong by getting more vegetables and more fiber.

Fat in Perspective. Researchers have also long suspected that a high-fat diet is a risk factor for colon cancer. Yet evidence is accumulating that fat per se isn't the real problem. Two large studies from Harvard found a link between colon cancer and fat from red meat. No increased risk was found from any other fat source, suggesting that some component of red meat other than fat is the culprit.

In one of the studies, men who ate red meat five or more times a week had almost four times the risk of colon cancer compared to those who ate meat less than once a month.

Watching Weight. Maintaining a reasonable weight can also help thwart colon cancer. People with a body mass index (BMI) of 25 or greater are twice as likely to develop colon cancer, compared to those with a BMI less than 25. (See EN, November 1998.) While excess calories are the usual villains in overweight, some researchers suggest exercise is the real link, since overweight people are often less active. Physical activity appears to help prevent colon cancer directly, possibly by stimulating the movement of food through the colon, similar to fiber's purported effect.

"Vigorous physical activity is the most consistently identified protective factor for colon cancer," adds Slattery.

Folate and Calcium. The B vitamin folate is the newest candidate to act as a shield against colon cancer. Harvard researchers found that people who consume more folate from food sources such as dark green leafy vegetables, fortified cereals and orange juice or from supplements (as folic acid) were less likely to develop colon cancer. Longterm multivitamin users saw the greatest benefit -- a 75% reduction in risk.

The case for calcium is growing. About 1,200 to 1,500 milligrams a day seems protective, says Peter Holt, M.D., of St. Luke's-Roosevelt Hospital Center in New York City. Holt notes that greater benefits have been seen with dietary calcium, namely dairy products, rather than supplemental calcium. This suggests that other substances in dairy foods may play a role.

The Lowdown on Alcohol. Avoiding heavy use of alcohol lowers your chances of colon cancer. Current guidelines urge limiting alcohol to less than two drinks a day for men and one drink a day for women. However, getting enough folate appears to offset some of the adverse effects of alcohol.

The Bottom Line. Adopting a healthy lifestyle affords the best chance of reducing your risk of colon cancer, even given a genetic tendency. Certainly, there are no guarantees, but eating right puts prevention within your reach.

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By Linda Antinoro, J.D., R.D.

Adapted by J.D., R.D.

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