The Major Intestinal Disaccharidase Switches from Lactase to Maltase with Maturity

Lactose from milk is the major carbohydrate in the diets of neonatal and young mammals; thus all mammals are born with high intestinal lactase activity. In contrast, maltase activity, necessary for digesting the products of luminal starch digestion, is weak or absent for several weeks after birth. As animals progress toward weaning, lactase activity wanes and maltase activity increases, allowing the animals to shift from lactose to starch as a carbohydrate source. In many species of adult animals, lactase activity is practically nonexistent.