Polysaccharides: bowel health and gut microbiota.

Polysaccharides that contain many sugar monomers include starch and non-starch polysaccharides (NSPs) together with resistant starch (RS). Dietary polysaccharides are well known to have a wide range of biological benefits for bowel health. Gut microbiota and their fermentative products, short chain fatty acids (SCFA), which have recently been highlighted as metabolic regulators, are thought to mediate the function of dietary complex carbohydrates and bowel health. We discuss the influence of various polysaccharides on human bowel health and the mechanisms underlying these effects. We also describe their biological effects on intestinal health and the mechanisms underlying their activity; the polysaccharides were divided into three categories: dietary, microbial, and host-derived polysaccharides. Physiological impacts of non-starch polysaccharides (NSPs) and resistant starch (RS), both of which pass through the small intestine nearly intact and can be fermented by gut microbiota in the large intestine, are similar to each other. They exert a wide range of beneficial effects including anti-inflammation, gut epithelial barrier protection, and immune modulation through both microbiota-dependent and -independent mechanisms. Bacterial polysaccharides usually found in the cell wall generally act as immune modulators, and host-derived polysaccharides not only protect host cells from pathogenic microbial neighbors but also affect overall intestinal health via interactions with gut microbes. Considering these observations, further studies on polysaccharides will be important for bowel health.