ABSTRACT
Colorectal cancer is a commonly diagnosed malignant disease and a major cause of cancer mortality. Epidemiologic studies suggest that colon cancer is environmental or dietary in origin, and thus, potentially preventable. Plant fiber is a key element in this dietary hypothesis, and diets rich in plant fiber have been hypothesized to play a preventive role in pathogenesis of human colon cancer. Dietary fiber itself is an extremely complex substance composed of individual polysaccharide and nonpolysaccharide polymers of plant cell wall origin. These include cellulose, hemicelluloses, pectin, lignin, and several other components. Foods that contain fiber contain substances that can be hydrolyzed by human alimentary tract enzymes, and these may undergo nutrient absorption. Intestinal microflora may convert both endogenous and exogenous agents into active luminal carcinogens, and these microbes appear to be sensitive to various dietary substrates, including fiber-containing foods. Changes in the metabolic activity of certain bacteria could occur without changes in the number or types of intestinal bacteria.
