The following report by medical editor Marilyn Brooks first aired Dec. 13, 2005, on Channel 4 Action News at 5 p.m.

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Some studies have shown that fiber can lower the risk of colon cancer.

However, a new study says there is no benefit.

It's advice many have followed for years: fruits, vegetables, cereals and whole grains lessen the risk of colon cancer.

"Well, I think I should be eating a fair amount of fiber. From what I understand, it's good for you. It's supposed to keep cancer at bay," said Jane Stevens. But does it really?

"There is no proven evidence that it does reduce your risk of colon cancer," said Dr. James Celebrezze, a colorectal surgeon.

"We found that eating a high-fiber diet was not associated with a lower risk of colorectal cancer," said Dr. Stephanie Warner of the Harvard School of Public Health.

Warner and her colleagues were part of a large international study that tracked the health and fiber-eating habits of more than 724,000 people for 20 years.

More than 8,000 developed colorectal cancer.

"We found that people who ate higher amounts of fiber had the same risk of developing colorectal cancer as individuals who ate lower amounts of fiber," said Warner.

The kind of fiber didn't matter. None of it affected colon cancer, although it slightly lowered the risk of rectal cancer.

In fact, experts like Celebrezze say the only thing proven to reduce the risk of developing and dying from colorectal cancer is routine screening with a colonoscopy.

They also say there is no one cause of colorectal cancer.

"The cancers start in the lining or the inside layer of the bowel and that's where the waste is," said Warner.

However, fiber does reduce the risk of heart disease and diabetes.