Fiber in the Diet:
Dietary fiber is the component in food not broken down by
digestive enzymes and secretions of the gastrointestinal tract.
This fiber includes hemicelluloses, pectins, gums, mucilages,
cellulose, (all carbohydrates) and lignin, the only non-carbohydrate
component of dietary fiber.
High fiber diets cause increased stool size and may help prevent
or cure constipation. Cereal fiber, especially bran, is most
effective at increasing stool size while pectin has little effect.
Lignin can be constipating.
Fiber may protect against the development of colon cancer,
for populations consuming high fiber diets have a low incidence
of this disease. The slow transit time (between eating and elimination)
associated with a low fiber intake would allow more time for
carcinogens present in the colon to initiate cancer. But constipated
people do not have a higher incidence of colon cancer than fast
eliminators, so fiber's role in colon cancer remains unclear.
Dietary fiber may limit cholesterol absorption by binding
bile acids. High fiber diets lower serum cholesterol and may
prevent cardiovascular disease. Some fibers, such as pectin and
rolled oats, are more effective than others, such as wheat, at
lowering serum cholesterol.
Dietary fiber is found only in plant foods such as fruits,
vegetables, nuts, and grains. Whole wheat bread contains more
fiber than white bread and apples contain more fiber than apple
juice, which shows that processing food generally removes fiber.
Adapted from: Fiber
in the Diet