Human Biochemistry, Volume 2 - Murray R. 1993

Special Topics
Nutrition, Digestion, and Absorption
Dietary Fiber Requirements

Dietary fiber consists of plant Cell wall components that are not broken down by animal digestive Enzymes; these include Cellulose, hemicellulose, Lignin, Gums, Pectins, and pentosans. In herbivores, particularly ruminants, fiber (primarily in the form of cellulose) serves as a major energy source following microbial Digestion.

In humans, a high-fiber diet exerts beneficial effects by promoting Water retention as food passes through the intestinal tract, thereby contributing to The formation of bulky, soft stools. Such a diet reduces the risk of diverticulosis, colon Cancer, cardiovascular disease, and type 2 diabetes. Low-solubility fibers, such as cellulose and lignin found in wheat bran, effectively support colon function, whereas more soluble fibers present in fruits and vegetables—such as gums and pectins—help lower Blood Cholesterol levels, likely by binding Bile acids and dietary cholesterol. Soluble fibers also delay gastric emptying, slowing and blunting the postprandial rise in blood glucose and consequently reducing Insulin secretion. This effect is particularly beneficial for diabetic patients and individuals on restricted diets, as it minimizes the subsequent drop in blood glucose (the rebound phenomenon) that typically stimulates appetite.