Inadequate amounts of lactase cause the body to be unable to digest lactose, a sugar found in milk products. Lactase is normally produced in the small intestine where it breaks lactose down into a form that can be absorbed by the blood. A lack of lactase can cause uncomfortable symptoms for some people. Those who do exhibit the symptoms are said to be lactose intolerant. Ninety percent of Asian-Americans are lactose intolerant.
Lactose intolerance is least common among people with a northern European heritage.
Digestive diseases or injuries to the small intestine can reduce the amount of enzymes produced, and is one usual cause of lactose intolerance in young children. However, most cases of lactose intolerance develop over a period of many years in adolescents and adults. The following are the most common symptoms for lactose intolerance. However, each individual may experience symptoms differently. The severity of symptoms varies depending on the amount of lactose consumed and the amount each individual can tolerate.