Lactose, also known as milk sugar, is a naturally occurring disaccharide found in milk and dairy products. Chemically, lactose consists of two simple sugars: glucose and galactose. In order for the body to be able to utilize lactose, it must be broken down into its components in the small intestine by the enzyme lactase. In people with lactose intolerance, not enough lactase is produced, which leads to digestive problems when lactose is consumed