Lactose is a disaccharide made up of the monosaccharides glucose and galactose, and is the primary carbohydrate found exclusively in mammalian milk (1,2). The absorption of lactose requires activity of the enzyme lactase to split the bond linking the two monosaccharides. Lactase is located in the small intestine along the brush border, mostly at the tips of the villi (1,2).

 

Lactase deficiency occurs when there are low concentrations of lactase in the small intestinal brush