Galactose is a type of sugar found in milk products and sugar beets. It is also made by the body. It is considered a nutritive sweetener because it has calories.
Galactose is a monosaccharide constituent, together with glucose, of the disaccharide lactose. The hydrolysis of lactose to glucose and galactose is catalyzed by the enzyme beta-galactosidase, a lactase.
Individuals who lack this enzyme are 'lactose intolerant' and unable to realize the nutritive potential of milk sugars. The lactose then passes to the large intestine where it is digested by bacteria, producing gas and flatulence.