ABSTRACT
Absorption of carbohydrates is essential to allow a child to grow and thrive. In newborns, lactose in milk forms the sole form of carbohydrate. This disaccharide is hydrolyzed into glucose and galactose by lactase in the small intestine.
After several months, other disaccharides and polysaccharides, particularly starch, become the predominant carbohydrate sources. These compounds are degraded in the small intestine primarily by sucrase-isomaltase, in concert with (Xamylase present in saliva and in pancreatic secretions. Degradation of starch yields glucose, whereas the degradation of sucrose yields equimolar amounts of glucose and fructose. The resulting monosaccharides-glucose, galactose, and fructose-are transported into the epithelium and then into the blood by specific transporters. Therefore, this chapter concentrates primarily on the two crucial enzymes in carbohydrate digestion, lactase and sucrase-isomaltase, and on three sugar transporter proteins, designated sodium-dependent glucose transporter-l (SGLTl), glucose transporter-2 (GLUT2), and glucose transporter-S (GLUTS), which are pivotal for the absorption of the monosaccharides into the enterocytes and their release into the blood.
