Gastrointestinal effects of food carbohydrate.

Dietary carbohydrate may be divided into monosaccharides and disaccharides (sugars), oligosaccharides [degree of polymerization (DP) 3-9], and polysaccharides (DP > 10). Their physiological properties and health benefits depend on the site, rate, and extent of their digestion or fermentation in the gut. Oligosaccharides are a diverse group of soluble carbohydrates, many of which are not digested by pancreatic enzymes. They are fermented in the colon and some have specific effects on bacteria. The major dietary polysaccharides are starch and nonstarch polysaccharides (NSPs). The digestion of starch depends on its physical form, the nature of the starch granule, and the effects of food processing. Starch may be rapidly digested, slowly digested, or resistant, the last passes into the colon for fermentation. The NSPs (cell wall polysaccharides) all resist digestion. They exert a physical effect in the upper gut, serving to moderate carbohydrate and possibly lipid absorption, whereas in the colon they affect bowel habit through fermentation, they affect epithelial cell metabolism, and, along with other fermented carbohydrates, they provide energy to humans.