Carbohydrate Digestion
Digestion of carbohydrates begins in the mouth where salivary amylase converts starch to dextrins and maltose. After the mouth, food travels to the stomach where carbohydrates remain unchanged due to denaturation of salivary amylase. The optimal pH of alpha amylase is 7. Hence, it is not able to survive the very low pH of the stomach (pH = 1.5 - 3.5).
Following the stomach, carbohydrates are digested by pancreatic amylase from the pancreas and by maltase present in the walls of the small intestine, producing glucose. Other enzymes secreted by the intestine include sucrase (converts sucrose to glucose and fructose), and lactase (converts lactose to glucose and galactose).
Glucose and other monosaccharides (fructose and galactose) are absorbed in the small intestine and into blood capillaries where some are stored as glycogen (glycogenesis). The rest are transported to the body to provide energy.
Some starch will reach the large intestine unchanged. These are known as resistant starch. They function as dietary fiber since they are fermented by bacteria to produce short chain fatty acids (SCFA) including acetate, propionate and butyrate. SCFA have been associated with improved gut health.
