What can fiber do for you? Numerous epidemiologic (population-based) studies have
found that diets low in saturated fat and cholesterol and high in fiber are associated with a
reduced risk of certain cancers, diabetes, digestive disorders, and heart disease. However, since
high-fiber foods may also contain antioxidant vitamins, phytochemicals, and other substances
that may offer protection against these diseases, researchers can't say for certain that fiber alone
is responsible for the reduced health risks they observe, notes Joyce Saltsman, a nutritionist with
FDA's Office of Food Labeling. "Moreover, no one knows whether one specific type of
fiber is more beneficial than another since fiber-rich foods tend to contain various types,"
she adds.
Recent findings on the health effects of fiber show it may play a role in:
Cancer: Epidemiologic studies have consistently noted an association
between low total fat and high fiber intakes and reduced incidence of colon cancer. A 1992 study
by researchers at Harvard Medical School found that men who consumed 12 grams of fiber a day
were twice as likely to develop precancerous colon changes as men whose daily fiber intake was
about 30 grams. The exact mechanism for reducing the risk is not known, but scientists theorize
that insoluble fiber adds bulk to stool, which in turn dilutes carcinogens and speeds their transit
through the lower intestines and out of the body.
The evidence that a high-fiber diet can protect against breast cancer is equivocal.
Researchers analyzing data from the Nurses' Health Study, which tracked 89,494 women for
eight years, concluded in 1992 that fiber intake has no influence on breast cancer risk in
middle-aged women. Previously, a review and analysis of 12 studies found a link between high
fiber intake and reduced risk.
In the early stages, some breast tumors are stimulated by excess amounts of estrogen
circulating in the bloodstream. Some scientists believe that fiber may hamper the growth of such
tumors by binding with estrogen in the intestine. This prevents the excess estrogen from being
reabsorbed into the bloodstream.
Digestive disorders: Because insoluble fiber aids digestion and adds bulk
to stool, it hastens passage of fecal material through the gut, thus helping to prevent or alleviate
constipation. Fiber also may help reduce the risk of diverticulosis, a condition in which small
pouches form in the colon wall (usually from the pressure of straining during bowel movements).
People who already have diverticulosis often find that increased fiber consumption can alleviate
symptoms, which include constipation and/or diarrhea, abdominal pain, flatulence, and mucus or
blood in the stool.
Diabetes: As with cholesterol, soluble fiber traps carbohydrates to slow
their digestion and absorption. In theory, this may help prevent wide swings in blood sugar level
throughout the day. Additionally, a new study from the Harvard School of Public Health,
published in the Feb. 12 issue of the Journal of the American Medical Association, suggests that
a high-sugar, low-fiber diet more than doubles women's risk of Type II (non-insulin-dependent)
diabetes. In the study, cereal fiber was associated with a 28 percent decreased risk, with fiber
from fruits and vegetables having no effect. In comparison, cola beverages, white bread, white
rice, and french fries increased the risk.
