Natural fiber and bowel dysfunction.

This paper reviews the current status of knowledge with relation to the effects of natural fiber on intestinal physiology. The one clear feature that emerges from literature is that most types of natural fiber increase the bulk of the stool. It is probable also that transit time is affected. Transit time appears to be decreased in persons with initially a slow time when they use certain forms of natural fiber and it may be that persons with rapid transit have a decrease in the rate of passage as fiber is added to the diet. Data on colonic intraluminal pressures are scanty, but those that exist seem to indicate that the addition of bran to the diet results in a decrease in overall colonic pressures. Much has been written and speculated about the role of natural fiber in the prevention or therapy of irritable colon and diverticular disease. Clinical studies, while enthusiastic, are preliminary and there are no hard data to indicate that the use of these materials are, in fact, helpful. Such clinical trials that have been published are, in general, small, poorly controlled and overall equivocal in their conclusions. A great deal of further work requires to be done to justify the claims that have been made on the role of fiber in altering normal or abnormal bowel habit.