Type 1 RS: Starch granules surrounded by indigestible plant matrix Type 2 RS: Found in natural form as high amylose content starch in maize, rice etc. Type 3 RS: Crystallized starches made by unique cooking and cooling processes Type 4 RS: Starch chemically modified by esterification, crosslinking, or transglycosylation Celluloses Hemicelluloses Gums Pectins Xylans Mannans Glucans Mucilages Lactose Fructose Sorbitol Lactitol Mannitol Maltitol Xylitol Fructooligosaccharides Raffinose Stachyose Inulin Polydextrose (used in food industry) In the study[12] Selleckchem PLX3397 cited in the previous section, in which three enterotypes

of the human gut microbiota were identified, metabolic pathway analysis led to some interesting conclusions. It suggested that the microbes of enterotype 1-derived energy mainly from the fermentation of carbohydrates and proteins, as they were enriched for genes representing saccharolytic enzymes, galactosidases, hexosaminidases, proteases, and enzymes in the glycolysis and pentose phosphate pathways. Enterotypes 2 and 3 were considered to derive energy significantly from mucin degradation, although the latter probably also had potential to utilize carbohydrates by fermentation by virtue of the presence VX-809 clinical trial of significant numbers of Bacteroides species. Enterotype 1 was enriched in enzymes involved in biosynthesis

of biotin, riboflavin, pantothenate, and ascorbate while enterotype 2 was enriched in enzymes involved in biosynthesis of thiamine and folate. Starch degradation enzymes increased with age, consistent with changing dietary patterns. Two marker modules that correlated strongly with host body mass index were identified to be ATPase complexes, reinforcing a link between gut microbiota and energy nutrition state in the host. Between 10% and 20% of ingested dietary carbohydrates are resistant to small intestinal digestion. These non-digestible dietary carbohydrates (NDC) include certain forms of starch that are resistant to amylase

digestion (resistant starch [RS]) as well as non-starch polysaccharides (NSPs) (Table 1).[24, 25] The NSP include substances such as pectin that are substrates for colonic FER bacterial metabolism, and substances such as cellulose that are not fermented by the colonic bacteria. Non-digestible dietary carbohydrates enter the colon where RS and fermentable NSP are fermented by colonic bacteria to SCFA, lactate, and gases such as CO2, H2, and methane (Fig. 1).[26, 27] RS, primarily from cereals but also from raw banana and potato, is a very important substrate for colonic fermentation.[24, 27, 28] While many commonly eaten foods have a significant content of type 2 RS (i.e. naturally present in the food source), the method of cooking and eating may enhance RS content of the food.