How much and what classes of carbohydrate reach the colon

On current estimates it is likely that about 30 g carbohydrate per day enters the colon. It is probable that our estimates of starch and its degradation products entering the colon, true resistant starch, in a physiological sense, are too low. With total starch intakes of the order of 150 g one might expect a contribution of the order of, for example, 15 g assuming a digestion/absorption efficiency of 90%. However, the digestion of starch and the hydrolysis of the disaccharides and malto-oligosaccharides in the brush border of the small intestine are extremely efficient, so that the overall efficiency of digestion/absorption will be very dependent on the physical structure and properties of foods. More detailed analyses of the oligosaccharides in foods, especially cereals, may lead to revised estimates. Estimates of the amounts of carbohydrates required to support the bacterial mass produced should also be examined more closely. It is also questionable whether estimates of breath hydrogen production on a typical diet are indicative of the current estimates of carbohydrate substrate required for the production of bacterial mass.