Fiber may bind colon carcinogens.

Fiber may bind colon carcinogens 

High-fiber diets have been associated with a reduced risk of human colon cancer. Possible explanations include: that fiber's bulk makes it less likely that carcinogens passing through the digestive tract will touch the colon's surface; that, by accelerating food's passage through the digestive tract, fiber reduces a carcinogen's time in contact with the colon's walls; and that fiber may bind to the carcinogens, pulling them out of the body before they can do harm. New research by food chemists at the University of Lund in Sweden offers further support for this last hypothesis.

The researchers used three chemicals known to produce tumors in the intestinal tract of laboratory animals. These heterocyclic amines--members of the quinoline family--form during the cooking of meats at high temperatures. In test tube environments meant to roughly simulate conditions that might occur during digestion, each was mixed with one of 13 different food fibers, including whole rye flour, whole barley flour, oat bran and wheat bran, among others.

According to a report of the work in the November-December JOURNAL OF FOOD SCIENCE, all fibers bound at least 8 percent of the quinolines, and some bound as much as 22 percent, depending on the fiber and the particular quinoline. In a category by itself was whole sorghum flour, which bound roughly 50 percent of the available quinoline, regardless of the quinoline concentration present.

This suggests that there may be different structural forms of these quinolines, with different binding affinities, says Padmanabhan Nair, a chemist with the Agriculture Department's Human Nutrition Research Center in Beltsville, Md. The researchers also found that an acidic pH caused maximum binding. But since the pH of the post-stomach phase of digestion is highly alkaline, Nair says, one should test whether fibers release quinoline in an alkaline environment.