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Colorectal Cancer Health Center

High-Fiber Diet Linked to Lower Colon Cancer Risk

Research Shows Fiber From Whole Grains and Cereals Associated With Reduced Colon Cancer Risk
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Fiber and Colorectal Cancer Risk continued...

The protective effect was seen no matter what the starting point was for fiber, he says. "If you have a low intake, like 5 grams a day, and increase it to 15, it will have an effect, too." In terms of risk reduction for colorectal cancer, however, he says, the more fiber, the better.

Adding three servings, or 90 grams a day, of whole grains was linked with about a 20% risk reduction. That's a lot of fiber, the equivalent of 6 cups of lentils.

In the U.S., women are advised to eat about 25 grams a day of fiber, men about 38 grams. One slice of whole-wheat bread has about 2 grams of fiber; a cup of oatmeal has 4 grams.

Experts are still debating exactly how fiber might reduce colorectal cancer risk. "We don't know for sure," Aune says.

One possibility is that the fiber may reduce risk by reducing the ''transit time" of food products in the digestive tract. The fiber may also dilute carcinogens in the colon.

Second Opinion

"There are a few things that are important for people to understand here," says Lona Sandon, MEd, RD, assistant professor at the University of Texas Southwestern and a spokeswoman for the American Dietetic Association.

She reviewed the findings for WebMD but was not involved in the study. "Colon cancer does not happen overnight," she says. It can take many years to develop. "So starting to eat whole grains in your 50s may not prevent colon cancer in your 60s."

"A poor diet is not the only reason colon cancer might develop, although it may encourage its growth and spread," she says. Other triggers for colon cancer, she says, include chronic inflammation, such as having inflammatory bowel disease.

"This does not prove cause and effect," she says of the study.

Even with the caveats, however, Sandon says the message is simple: "Eat more whole grains." While not all the answers are in on how they might reduce colorectal cancer risk, they and other sources of fiber have other health benefits.

Among them:

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