Home > Encyclopedia of Medicine > Lactose Intolerance

Definition

Lactose intolerance refers to the inability of the body to digest lactose.

Description

Lactose is the form of sugar present in milk. The enzyme lactase, which is normally produced by cells lining the small intestine, breaks down lactose into substances that can be absorbed into the bloodstream. When dairy products are ingested, the lactose reaches the digestive system and is broken down by lactase into the simpler sugars glucose and galactose. The liver changes the galactose into glucose, which then enters the bloodstream and raises the blood glucose level. Lactose intolerance occurs when, due to a deficiency of lactase, lactose is not completely broken down and the glucose level does not rise. While not usually dangerous, lactose intolerance can cause severe discomfort.

From 30 to 50 million Americans suffer from the symptoms of lactose intolerance, but not everyone who is deficient in lactase...