Fibers resist rapid digestion in the intestinal tract. The main component of cereal fiber is hemicellulose. Hemicellulose is common in fruits and vegetables and is also resistant to digestion. Higher concentrations of soluble fibers are found in fruits, oats, barley and legumes. Soluble fibers generally slow the emptying of the stomach, slow glucose absorption and aid in lowering blood cholesterol.
Insoluble fibers are high in vegetables, wheat and cereals.
Dietary fiber is the nondigestible form of carbohydrate that is of nutritional importance in gastrointestinal disease. Unlike fat, carbohydrates have very little storage in the body. Liver glycogen is the primary glucose source available for the body. Glucose is the primary energy source for the brain and nerves. Rapidly digested carbohydrates can cause a major increase in insulin.