Lactose is a disaccharide commonly found in milk, like the milk shown above. It is composed of equal parts of galactose and glucose (two monosaccharides), and it basically means “milk sugar”. Lactose intolerance is when the body is unable to digest lactose because it stops producing lactase. Europeans generally have the ability to digest lactose. However, most infants stop producing lactase after infanthood because most mammals in the wild do not need to drink milk after growing past the infant stage. When a person is unable to digest lactose, the lactose passes on into the large intestine, where the gut flora, or the bacteria within the intestines, take it in for energy. This causes the overall uncomfortable symptoms of lactose intolerance.