Dietary fiber (found mostly in plant foods) is the part of food that is not digested by the human body,
such as the skin of an apple and the husk of a wheat kernel. The normal functioning of the intestinal tract
depends upon the presence of adequate fiber. There are two broad classes of dietary fiber, water-soluble
and insoluble. Insoluble fiber (roughage) is associated with hastening food through the digestive tract and
has a well deserved reputation for promoting 'regular' bowel movements. Soluble fiber, though
contributing to regularity, is more often thought of in the context of reducing the risks of heart disease and
diabetes. Soluble fiber has a subtle impact on the body's metabolism of sugars and fats. Jean Carper says
that insoluble fiber may help prevent digestive problems such as diverticulosis, constipation and colon
cancer. She goes on to say that soluble fiber works against high blood pressure, glucose intolerance and
high blood cholestrol. Therefore, it is suggested that we consume _both_ types of fiber.
How much fiber? The American Dietetic Association recommends 20-35 grams of dietary fiber.
Duarte says that when Americans started going from 17 grams per day to 46 grams per day of fiber, their
increased fecal weight went from 79 to 228 grams. In 1988, C. Everett Koop (surgeon general) said that
35 grams was sufficient to generate the kinds of results desired. It is important to have larger, healthier
stools (softer and laden with water) because they are easier to pass and they have a shorter transit time.
Thus, toxic substances such as cancer producing agents are excreted in feces without lingering in the colon.
Dietary fiber also excretes bile and bile is what the liver uses to produce cholestrol.
Be careful about too much fiber too soon. Overindulgence can cause bloating, constipation or diarrhea.
One tablespoon of fiber will give you approximately 10 grams of additional dietary fiber. Insoluble fiber is
found mostly in whole grains (ie. wheat bran and oat bran) it is also found in raw blackberries, lima beans
and peas. . Soluble fiber can be found in psyllium, beans, barley and oats. Most complex carbohydrates
are a mixture of both types of fiber.
There are six major fiber components: CELLULOSE/HEMICELLULOSE--insoluble, absorbs
water/laxative effect; LIGNIN--insoluble, absorbs little water/lowers cholestrol; GUMS/PECTIN--
soluble, decreased fat absorption/lowers cholesterol/slows sugar absorption; MUCILAGES--soluble.
There are potential problems with increased fiber consumption. Foods containing fiber are known to
lower the bioavailibility of minerals. In part because of the ability of certain fibers to bind minerals and
increase their fecal excretion. And, because of certain phytates and oxalates, which bind trace minerals.
Minerals are more likely to be compromised in those who do not supplement their mineral intake while
consuming high levels of fiber supplements. Intestinal obstructions may occur in people with pre-existing
gastrointestinal problems and in those who fail to consume adequate water. It is advisable to check with a
physician before self-diagnosing and administering supplemental fiber. Complex carbohydrate foods
(whole grains) and cruciferous vegetables (brocolli, brussels sprouts, cabbage and cauliflower) are
excellent sources of dietary fiber.
Fiber products MUST be taken with plenty of water. Products like Psyllium and ProFibe absorb
a great deal of liquid and may get lodged in the intestinal trat if not accompanied with enough liquid.
A tablespoon of fiber product in a 10 ounce glass of water would be a good rule of thumb in my
opinion.
Bibliography:
Duarte, Alex, O.D. "Health Alternatives", 1995.
Passwater, R.A. "Dietary Fiber", 1988.
"Nutrition Alamnac",New and Expanded, 4/e, by Gayla J. Kirschmann, John D. Kirschmann
"Jean Carper's Total Nutrition Guide", 1989., by Carper, Jean.
"The Doctor's Vitamin and Mineral Encyclopedia", 1991., Hendler, Sheldon Saul, M.D.
"Modern Nutrition in health and disease", 8th. edition, 1994., by Shils, Olson and Shike
"Refined Carbohydrate Foods and Disease", 1975., by Trowell, H.C., Burkitt, D.P.
"Dietary Fiber : Chemistry, Physiology, and Health Effects", 1990, by Gayla J. Kirschmann, John D. Kirschmann
"CRC Handbook of Dietary Fiber in Human Nutrition", by Gene A. Spiller (Editor)
"Dietary Fiber in Health and Disease (Advances in Experimental Medicine and Biology, Vol 427)",
by David Kritchevsky (Editor), Charles Bonfield (Editor)