Maybe. Fiber might play a role in protecting you from colon cancer, according to two major studies.

People who ate the most fiber had a drastic reduction in their risk of colon cancer. Diets averaging 35 grams of fiber a day translated into the risk for colon cancer dropping by 40 percent, compared to people eating only 15 grams, according to the largest scientific study to investigate the links between diet and cancer risk.

The European Prospective Investigation into Cancer (EPIC) report, published in May in the British medical journal The Lancet, tracked the diets of a half million people in 10 European countries for an average of four-and-a-half years.

Complementing that study is a separate report from the United States appearing in the same journal issue. People who ate more than 30 grams a day had their risk of polyps reduced by 20 percent compared to those who ate less than 15 grams.

Scientists with the Prostate, Lung, Colorectal and Ovarian Cancer Screening project team compared the fiber intakes of 34,000 subjects without colon polyps.

Experts say while these results are encouraging, this research still does not prove how fiber prevents colon cancer or if fiber works alone.

Other health habits?

However, many other studies show a spectrum of answers, baffling researchers and consumers alike.

It's hard to pinpoint fiber alone as a factor. This is probably because diets high in fiber are high in many other potentially protective factors such as folate and other vitamins. Also, people who consume high fiber diets also tend to follow other healthy lifestyle behaviors by exercising and not smoking, says Marjorie McCullough, D.Sc., R.D., an epidemiology researcher at the American Cancer Society.

People with high-fiber diets also are more likely to eat less red meat, drink less alcohol, smoke less and get regular exercise - all healthy behaviors that can reduce any kind of cancer risk.

Previous studies looking solely at fiber and colon cancer say dietary fiber may not be the magic ingredient that reduces the risk of colorectal cancer and adenomas. A major 1999 report, published in the New England Journal of Medicine, looked at 88,000 women participating in the Nurses' Health Study. The women were followed for 16 years. Little, if any, link between reduced colon cancer risk and fiber consumption existed. Also, studies from Finland and Sweden have found no protective effect from fiber.

Traditionally, researchers have several reasons for thinking fiber would protect against colon cancer, McCullough says. One theory suggests that by binding carcinogens and reducing constipation fiber might reduce the time that carcinogens interact with cells in the colon. Another theory suggests certain compounds produced in the colon when fiber is eaten may be healthy for colon cells.

If you look at the EPIC study, you'll see that the association with fiber and colon cancer is not enormously strong, says Joel Weissfeld, M.D., associate professor in the Department of Epidemiology of the University of Pittsburgh Medical Center. He explains the study does not address the differences of diets in varying cultures and the mixture of fiber. Fiber is found in whole grains, cereals with ingredients like bran, beans, fruits and vegetables. Generally, the European study was high in grains and cereal.

The question is: How much fiber is protective, and what kind of fiber would that be? he says, noting that eating more than the recommended amount of 30 grams of fiber a day does not show an additional benefit.

It could be that fiber intake doesn't do much by itself. Consuming calcium could be a link in helping to prevent colon cancer. Also, people following healthy diets and regular exercise tend to have lower glycemic levels.

We don't know how much of a role dietary fiber plays in preventing colon cancer or if there are other factors. There will always be that uncertainty. When you are dealing with complex diseases like colon cancer, there may not be one cause or one intervention. Which factor it may be, we may never know.