Physiologic Roles of Dietary Fiber
Certain physical properties of fiber such as particle size influence its effect in the gastrointestinal tract. Important characteristics of dietary fiber in relation to its physiologic role include hydration, capacity, adsorptive attraction for organic molecules, cation exchange capacity and fermentability. Fiber exerts its effect throughout the gastrointestinal tract beginning in the mouth. Fiber components that cannot be solubilized (lignin, cellulose and most of the hemicellulose) require increased chewing, thereby stimulating, saliva secretion and serving somewhat as a tooth cleanser.
Often dietary fiber is classified as soluble or insoluble in order to more easily explain its physiological functions. This classification is imprecise, however, because determination of soluble fiber is very difficult and the amount resulting from fiber analysis is influenced by the method used.
The food providing dietary fiber can have a decisive influence in the gastrointestinal tract responses elicited because sources of fiber vary in the relative amount of the different fiber components. For example wheat bran, is primarily hemicellulose, while most fruits, and vegetables contain almost equal quantities of cellulose and pectin. Dietary fiber composition of
plant depends on the plant species, the part of the plant consumed (leaf, root, stem) and its maturity. For example lignin is found relatively small amounts in edible plants; its content is highest in fruits with edible seeds, such as strawberries, and in mature root vegetables, such as carrots.
Physiologic Roles of Dietary Fiber
