An important but frequently neglected aspect of nutrition is dietary fiber. Fiber is the component in diet that can not be digested because humans lack the necessary enzymes.   It is therefore passed through the intestines and excreted in the stool. One may ask why an indigestible foodstuff is important for nutrition. The answer is multifaceted as a diet high in fiber offers a number of health advantages.

Increasing dietary fiber not only lowers the blood cholesterol level, but also improves the LDL (bad cholesterol) to HDL (good cholesterol) ratio. Soluble fibers (pectin, psyllium, gum) in the intestinal tract bind cholesterol and bile acids making them unavailable for absorption. Since LDL cholesterol is consumed in the manufacture of bile acids, the "bad cholesterol" level is primarily decreased. The degree of benefit is proportional to the amount of fiber in the diet. In general, high cholesterol levels (1) decrease by larger percentages than lower cholesterol levels in response to increasing fiber intake. Nevertheless, even a 1% decrease in the cholesterol level reduces the risk of heart disease by 2%.

Numerous studies implicate an association between a high fiber diet and lower risk of colon cancer. Insoluble dietary fiber (cellulose) increases the bulk and water content of the stool resulting in decreased intestinal transit time. It is believed that the decrease transit time reduces colon exposure to carcinogens leading to a lower risk of colon cancer.

The changes in stool consistency and transit time effected by insoluble fibers also improves bowel regularity. Fiber supplements are therefore helpful in the treatment of constipation as well as diarrhea. For the same reason, high fiber diets are beneficial in the prevention and treatment of hemorrhoids and diverticulosis, a weakening of the intestinal wall.

A fiber supplement beverage taken before meals frequently leads to a sensation of fullness. Individuals who gage their food intake based on satiety will likely experience a decrease in caloric intake. Therefore, fiber supplements may be useful as primary or adjunctive therapy in the treatment of obesity.

Fiber supplements taken before meals may also be helpful in glucose control in diabetics. Fiber in the intestinal tract slows (but does not interfere with) the absorption of food during a meal. This results in a blunting of the rise in postprandial glucose and improved blood sugar control. Supplements which contain chromium offer additional benefits, as chromium potentiates the action of insulin.

In summary, increasing dietary fiber offers a number of health advantages. By lowering cholesterol, it reduces the risk of heart and cerebral vascular disease. It is useful in the treatment of a variety of gastrointestinal disorders, obesity and  aids glucose control in diabetics.

1.  A cholesterol level less than 200 mg/dl is considered desirable; 200 to 239 mg/dl is borderline high; greater than 240 mg/dl is hypercholesterolemia; from Mahan KL, Escott-Sump S: Food, Nutrition, and Diet Therapy, 9^th ed, Philadelphia, WB Saunders, 1996