Lactose is the naturally occurring sugar found in milk and most other dairy products. It’s a disaccharide, meaning it’s formed by the bonding together of two simple monosaccharides -- glucose and galactose. The small intestine produces an enzyme called lactase, which breaks milk sugar down into its component sugars for absorption and conversion into usable energy. Although lactose intolerance brought about by a lactase deficiency can affect people of any age, the condition is more common in adults than it is in children, according to the National Digestive Diseases Information Clearinghouse.
