The term ‘dietary fiber’ (DF) was first introduced in 1950s, referring to plant cell wall materials; later it was used to describe a class of plant-originated polysaccharides, which cannot be digested and absorbed in the gastrointestinal tract.
It is now recognized that an addition of fiber to the diet, especially soluble and semi-soluble fibers offer many health benefits. Cellulose, hemicellulose and lignin- are not soluble in water whereas pectins, gums and mucilages- become gummy in water.
Soluble fiber dissolves in water forming viscous gels. They bypass the digestion of the small intestine and are easily fermented by the microflora of the large intestine. In the human GI tract, insoluble fibers are not water soluble. They do not form gels due to their water insolubility and fermentation is severally limited.
The main sources of soluble fiber are fruits and vegetables. Conversely, cereals and whole-grain products provide sources of insoluble fiber. However, most naturally available high-fiber foods contain variable amounts of both soluble and insoluble fiber.
Diets, deficient in dietary fiber, lead to a number of diseases such as constipation, hiatus hernia, appendicitis, diabetes, obesity, coronary heart diseases, gallstones, etc. Consumption of adequate amounts of dietary fiber reduces the risk of mentioned diseases.
Dietary fiber
