<P> Even though these complex polysaccharides are not very digestible, they provide important dietary elements for humans . Called dietary fiber, these carbohydrates enhance digestion among other benefits . The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed . Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this in turn lowers cholesterol levels in the blood . Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short - chain fatty acids as byproducts with wide - ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown . </P> <P> Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake . </P> <P> Starch is a glucose polymer in which glucopyranose units are bonded by alpha - linkages . It is made up of a mixture of amylose (15--20%) and amylopectin (80--85%). Amylose consists of a linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units (every chain of 24--30 glucose units is one unit of Amylopectin). Starches are insoluble in water . They can be digested by breaking the alpha - linkages (glycosidic bonds). Both humans and animals have amylases, so they can digest starches . Potato, rice, wheat, and maize are major sources of starch in the human diet . The formations of starches are the ways that plants store glucose . </P> <P> Glycogen serves as the secondary long - term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue . Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach . </P>

Polysaccharides are often called complex carbohydrates and they primarily include