Interaction of dietary fiber with other dietary components: a possible factor in certain cancer etiologies.

Dietary fiber is a highly interacting dietary component and is made up of a wide variety of enzyme-indigestible polymers: cellulose, pectins, gums, mucilages, lignin, and water-insoluble hemicelluloses. The study of the effect of dietary fiber on prevention of cancer, specifically of colonic cancer, cannot be carried on without considering that: 1) various types of dietary fiber have different metabolic effect; 2) other components of the diet (e.g., amount of fat) may influence the way dietary fiber affects the colonic environment; 3) the overall effect of dietary fiber may be the sum of effects on fecal bulk, colonic microflora pattern and metabolites, dilution of carcinogens, colonic pH, transit time, alteration of nutrient absorption, and postprandial hormonal function. It is unlikely that dietary fiber can be studied in isolation in experimental diets unless great care is taken to consider all interactions with other dietary components.