Can a fiber-rich diet alone help protect against the second most common cause of cancer mortality in the U.S.?

Possibly, according to new research which shows that dietary wheat bran fiber and the antioxidant beta carotene act as independent protective agents in reducing the risk ot colon cancer in typical high fat, western diets.

Researchers, led by Oliver Alabaster, M.D., director of George Washington University's Institute for Disease Prevention in Washington, D.C., evaluated the effects of wheat bran fiber and beta carotene, two known protectors against colon cancer, in helping to decrease the risk of this disease. The study, conducted on rats fed high-fat diets, was designed to determine whether beta carotene, when added to a high-fat, low-fiber diet, can circumvent the need to increase dietary fiber.

It also examined whether beta carotene combined with high levels of wheat bran fiber in the same high-fat diet can offer further protection.

The researchers observed a strong, independent protective effect of both beta carotene and wheat bran fiber against colon cancer in rats consuming a high-fat diet. What's more, they found that a diet containing both wheat bran fiber and beta carotene offered the greatest protection against precancerous cells and tumors of the colon.

"Our observations suggest that Americans can lower their risk of colon cancer simply by adding more dietary wheat bran fiber and beta carotene even when the overall diet is high in fat," declares Dr. Alabaster. "These findings are particularly meaningful because the consumption of rich, fatty foods continues to be entrenched in the dietary habits of Americans today."

During the 30-week study, rats were placed into two groups--one group was fed a high fat and low-wheat bran fiber diet and the other was given a high-fat and high-wheat bran fiber diet. Each group received different levels of beta carotene. The researchers administered wheat bran fiber and beta carotene in amounts that are nutritionally relevant to dietary intake in humans (40 grams of fiber/day; 20 mg beta carotene/kg body weight/day). The rats were then given injections of either a colon cancer-causing agent or a saline solution. After following a prescribed course, the subjects were evaluated on the comparative effect of different dietary regimens in the initiation of precancerous cells in the colon and the actual development of tumors.

The results show that as both the wheat bran fiber and beta carotene increases in the diet, the incidence of precancerous colon cells and resulting tumors in the rats decreased significantly, despite the high-fat diet. Moreover, the research findings reveal that each diet--a high-wheat bran fiber diet without beta carotene and a low-fiber diet supplemented with beta carotene--independently protects against the development of precancerous colon cells and tumors. The researchers found that the cancer-preventive effect of beta carotene in association with a low-fiber diet was comparable to that of a high-fiber diet without beta carotene.

"Most Americans today continue to consume too much fat, inadequate amounts of dietary fiber (an average of 11 grams per day) and little beta carotene in their daily diet," states Dr. Alabaster. "If people could simply eat more wheat bran-rich foods--like wheat bran-based cereals and wheat breads--as well as more beta carotene-rich fruits and vegetables, they may help reduce their risk of developing colon cancer."

This research was funded in part by the Cancer Research Foundation of America, a non-profit organization devoted to cancer prevention and childhood cancer.

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