<P> Digestion of starch begins with the action of salivary alpha - amylase / ptyalin , although its activity is slight in comparison with that of pancreatic amylase in the small intestine . Amylase hydrolyzes starch to alpha - dextrin , which are then digested by gluco - amylase ( alpha - dextrinases ) to maltose and maltotriose . The products of digestion of alpha - amylase and alpha - dextrinase , along with dietary disaccharides are hydrolyzed to their corresponding monosaccharides by enzymes ( maltase , isomaltase , sucrase and lactase ) present in the brush border of the small intestine . In the typical Western diet , digestion and absorption of carbohydrates is fast and takes place usually in the upper small intestine . However , when the diet contains carbohydrates not easily digestible , digestion and absorption take place mainly in the ileal portion of the intestine . </P>
where does the complete digestion of carbohydrates occur
the upper small intestine the ileal portion of the intestine