Abstract

Dietary fiber is a complex mixture of nondigestible polysaccharides and lignin, the exact composition depends on the plant or other food source, maturity, growing conditions, and processing. Plant cell wall polysaccharides are extensively fermented by the microbial enzymes in the lower digestive tract. The particle size and shape, density, crystallinity, water-holding capacity, and the level and type of dietary fiber affect the rate of passage of the digests through the digestive tract. Dietary fiber itself and the microbial fermentation in the colon give rise to various beneficial physiological effects. Dietary sources of soluble and insoluble fiber and their properties and methods for analysis are summarized. Specific food sources of dietary fiber are given. Fiber supplements are discussed.