<P> Digestion of food continues while simplest elements are absorbed . The absorption of most digested food occurs in the small intestine through the brush border of the epithelium covering the villi (small hair - like structure). It is not a simple diffusion of substances, but is active and requires energy use by the epithelial cells . </P> <P> During the phase of carbohydrate absorption, fructose is transported into the intestinal cell's cytosol, glucose and galactose competes with other sodium transporter required for operation . From the cytosol, monosaccharides pass into the capillaries by simple or facilitated diffusion . </P> <P> Carbohydrates not digested in the small intestine, including resistant starch foods such as potato, bean, oat, wheat flour, and several monosaccharide oligosaccharides and starch, are digested in a variable when they reach the large intestine . The bacterial flora metabolize these compounds anaerobically in the absence of oxygen . This produces gases (hydrogen, carbon dioxide and methane) and short - chain fatty acids (acetate, propionate, butyrate). The gases are absorbed and excreted by breathing or through the anus (flatulence). Fatty acids are rapidly metabolized . Butyrate is used mainly by cells in the colon and acetate is absorbed into the blood and taken up by the liver, muscle and other tissue . Propionate is an important precursor of glucose in some animals, but not humans . </P>

Where does the final stage of carbohydrate digestion occur