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Fiber - Natural

Fiber - Natural

Botanical Description & Habitat

Not Available

See also:
Fiber Products
High Fiber Diet
Low Fiber Diet

Historical Properties & Uses

Dietary fiber is vegetable substance not digestible by the enzymes of the alimentary tract. They are derived from plant cell walls and from the nonstructural polysaccharides in natural foods. Fibers include cellulosics and hemicellulosics, gums, pectins, and lignins.

Brans and pectins obtained from dietary sources are probably the most effective types of fiber. Experimental trials indicate fiber protects blood and tissue against various dietary and environmental toxins and carcinogens by maintaining the good health of the bowel, and rendering toxins inert by complexing with them.

Low fiber intake is conclusively related to obesity, diabetes mellitus, coronary heart disease, diseases of the colon--including cancer--and to various other modern ailments. A high fiber diet lead to decreases in body weight, blood sugar levels, serum cholesterol levels, and levels of total triglycerides, with corresponding improvements in health. Low concentrations of serum lipids and low incidence of coronary heart disease are found in Seventh Day Adventists, Trappist monks, strict vegetarians, lacto-vegetarians, and those using the Zen macrobiotic diet.

Method of Action

Dietary fiber reduces serum cholesterol levels
Not all dietary fibers produce the same metabolic effects. It is helpful, therefore, to sub-divide fibers into groups according to their mode of action.

1. Cellulosics and hemicellulosics include those non-digestible portions of many plants, including bran, cereals, grains, beans, peppers, carrots and cabbage, that absorb water, and increase in bulk. They have a normalizing effect on the bowel, prevent constipation by accelerating the passage of material through the large intestine, and protect the body from several diseases, including cancer, colitis, and spastic colon.

2. Gums include the extremely water loving material found in oats, guar, irish moss and locust beans, to name a few. Gums are also inert, simply absorbing water, swelling, and serving much the same purpose as the cellulosics.

3. Pectins are the water soluble substances bonding adjacent cell walls in the tissues of many plants, including apples, citrus fruits, potatoes, strawberries and green beans. They yield a gel which is the basis of fruit jellies. Pectins and gums bind with bile acids, and decrease cholesterol levels and fat absorption.

4. Lignins are plant polymers that combine with cellulose to form plant cell walls and the cementing material between them. Lignin has been found to reduce time of passage of stomach contents, bind with bile acids and lower cholesterol levels. Pectin has the greatest effect on cholesterol levels.

In 1957, it was found the dietary pectin (in rats) increased the excretion of lipids, cholesterol and bile acids. Thereafter, an increasing number of reports verified those data and extended them to include humans. By 1977, the effect had been thoroughly documented and established. For example, in one three week study in humans, plasma cholesterol fell about 13% or more as long as apple pectin was administered (about 15 gm/day). When the pectic was withdrawn, cholesterol levels rose. It is believed pectins operate by binding with bile acids, thereby decreasing cholesterol and fat absorption. The results of most experiments indicate mucilaginous fibers such as pectin, plantain and fenugreek are much better in decreasing serum cholesterol levels than are particulate fibers such as are found in wheat bran.

It is important to note pectin reduces lymphatic cholesterol absorption best when the diet contains cholesterol. (Pectin is also effective when used for producing regressions in, and preventing the formation of, gallstones). A few studies show bran from wheat, corn and sugar beets lowers serum cholesterol levels, but most data fail to show a significant effect in that direction.

The presence of other dietary factors may finally determine to what extent bran is effective. Oat bran, which is partly mucilaginous, does lower cholesterol levels substantially. Cellulose does not lower cholesterol levels except when administered in large quantities, and lignins have variable effects.

In summary, it appears mucilaginous fiber (pectin, oat bran) rather than particulate fiber (cellulosics, most brans, lignins) is responsible for decreased serum cholesterol levels. Several mechanisms have been postulated to explain the effects of fiber. It may alter gastric emptying time and intestinal transit rates, thereby decreasing the availability of carbohydrates to be absorbed. Or, since dietary fibers swell (each part of polysaccharide may hold 100 parts water), they may simply be filling, limiting the amount of food eaten. In this manner, the fiber actually displaces foods that contribute saturated fat and cholesterol to the diet.

By modulating glucose absorption, dietary fiber could prevent or reduce obesity. The most likely explanation is the mucilaginous fibers form gels in the small intestine interfering with the absorption of both cholesterol and bile acids. This hypothesis is supported directly by the finding pectin reduces lymphatic cholesterol absorption best when the diet contains cholesterol.

Pectin also increases the excretion of neutral bile acids because its ionic charge imparts a high affinity for solubilized biliary salts. Pectin-salt complexes are excreted as waste, resulting in a reduction of the available biliary salts which would normally be used by the body to make possible the absorption of cholesterol. This, in turn, may indirectly lower cholesterol levels even further because the body will now use up even more endogenous (non-dietary) cholesterol to produce more biliary acids.

Bran, though it doesn't lower cholesterol levels as surely as pectin does, has nevertheless been shown to help prevent the precipitation of cholesterol from the bile that produces gallstones. Bile is a finely balanced solution of cholesterol, bile salts and phospholipids. The oversecretion of cholesterol or the undersecretion of bile salts leads to supersaturation of cholesterol that then precipitates as gallstones. Bran increases the size of the bile salt pools when necessary and otherwise normalizes the balance between the major components of the bile. Thirty grams of bran per day has been shown to significantly improve the bile composition in several patients with cholesterol gallstones.

Pectin and other dietary fiber protects the body from toxins
Russian research has shown that heavy metals, such as lead and mercury, are excreted harmlessly and much more efficiently when pectin is included in the diet. Apple pectin, rice bran, wheat bran, alfalfa fiber and burdock root fiber, along with other sources of dietary fiber, have been shown to protect the body, and especially the gut, against the toxic effects of several common food additives, including amaranth (FD & C No. 2), Tween 60 (polyoxyethylen sorbitan monostearate), sodium cyclamate, tartrazine (FD 7 C Yellow No. 5), and Sunset Yellow (FD & C Yellow No. 6). Possible modes of action include a binding of the additives with the fiber, thereby preventing absorption, or perhaps the fiber prevents adverse effects through an action on the digestive process or gut bacteria.

Pectin may be used in the management of diabetes
There is growing evidence the regular use of pectin may lessen the severity of diabetes, presumably because pectin absorbs sugars and carbohydrates, releasing them slowly in the intestinal tract. This slow release produces a much slower and steady rise in blood sugar levels. It has been suggested a low fiber diet actually may precipitate diabetes mellitus.

One study showed adding pectin (and guar) to meals significantly reduced glucose and insulin levels in nondiabetic as well as non-insulin-requiring diabetic patients following meals. Insulin-requiring patients experienced a lowering of glucose levels. In a similar study, insulin-requiring diabetic patients experienced a continuing effect of lowered plasma glucose when placed on a long term pectin-rich diet. These patients eventually required much less insulin.

Drug Interactions & Precautions

Known interactions
It is known the use of dietary fiber, especially pectin, can eventually produce long lasting reduction of blood glucose levels. This in turn would potentiate the effects of insulin injections.

Possible interactions
None.

Comments
The use of large amounts of fiber on a continuous basis may partially block the digestion, absorption or reabsorption of a wide variety of drugs and fat-soluble vitamins.

The antidiabetic ability of fiber may be decreased by concomitant use of acetazolamide, oral contraceptive, corticosteroids, dextrothyroxin, epinephrine, ethanol, glucagon, and marijuana.

Antidiabetic effects of fiber may be decreased when used in conjunction with phenothiazines, rifampin, thiazide diuretics, and thyroid hormones.

The antidiabetic action of fiber may be enhanced when it is used with allopurinal, anabolic steroids, chloramphenicol, clofibrate, MAOI's, fenfluramine, guanethidine, phenylbutazone, probenecid and pheynramidol.

The antidiabetic action of fiber may be enhanced when used in conjunction with salicylates, sulfinpyrazone, sulfonamides, and tetracyclines.

Safety Factors & Toxicity

The toxicity level of fiber has not been determined at this time.

Preparation & Administration

There is presently insufficient data on this subject.

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