| Popis: |
Dietary fiber is a complex heterogeneous material increasingly used in the management of colorectal and other disease. Dietary fiber can be defined as that component of plant cells resistant to human alimentary enzyme action (Trowell, 1974). Some studies of fiber have shown a degree of hydrolysis by colonic bacteria. However, which components of fiber are hydrolyzed and the extent of their breakdown in the human colon are not clear. Not enough is known of the metabolism of fiber in the colon. The effect of dietary fiber on gastrointestinal function in man depends on the type of fiber (Royal College of Physicians, 1981). It is now appreciated that cereals, bran, and vegetable fiber behave differently along the gastrointestinal tract (Stephens and Cummings, 1980). Indirect evidence suggests that the cecum is a major site for metabolism of certain fibers. Anaerobic bacteria in the colon produce methane, hydrogen, volatile fatty acids, and carbon dioxide. It has been suggested that the fiber affects stool weight either directly (Smith et al., 1981), by bacterial mass (Stephens and Cummings, 1980), or by volatile fatty acids (VFA) derived therefrom (Hellendoorn, 1978). Retention of water by the fiber matrix as with cereal bran influences stool weight (Smith et al., 1981). |
