Amount of carbohydrate entering the colon
It is difficult to measure the amount of carbohydrate entering the human colon. However, it has been esti-mated that at least 30 g of carbohydrate is required to support the growth of the bacterial population in the colon of an individual on a typical Western diet pro-ducing about 100 g stool per day. About half of that amount will come from nonstarch polysaccharide (NSP, also known as dietary fiber), 1–2 g from indi- gestible oligosaccharides, and probably about 1–2 g from intestinal mucopolysaccharides. These compo-nents add up to only 18–20 g. Where does the other 10–12 g come from? It is believed to come from starch, because experiments in humans show that about 5– 15% of the starch in foods enters the colon. Typical Western diets contain about 120–150 g starch per day, and, if 8% of this enters the colon, this will provide the additional 10–12 g carbohydrate. The amount of carbohydrate entering the colon, however, can be increased several-fold, up to 100 g/day or more, by changes in diet such as increased intake of NSP, non-digestible or partially digestible carbohydrates (ingredients in functional foods), total starch, resis-tant starch, or slowly digested, low-GI foods.