Lactose Intolerance Health Article

Definition

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

Description

Lactose is the predominant 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, which can then be absorbed into the bloodstream. Lactose intolerance occurs when, due to a deficiency of lactase, lactose is not completely broken down and consequently blood sugar levels do not rise. While not usually a dangerous condition, lactose intolerance can cause severe discomfort.

Lactose intolerance is also referred to as lactase deficiency, milk intolerance, dairy product intolerance, or disaccharidase deficiency.

Demographics

From 30 to 50 million Americans suffer from the symptoms of lactose intolerance by the age of 20. People from cultures in which adult consumption of milk and milk products occurred earliest are less likely to be lactose intolerant than people from areas where dairy farming began more recently. The prevalence of deficiency in production of the lactase enzyme, therefore, varies among different ethnic groups. Among Asian populations it is almost 100 percent, with symptoms occurring around the age of five; among Native Americans it is 80 percent; among blacks it is 70 percent, with symptoms appearing by the age of 10; and among American Caucasians, the prevalence of lactose intolerance is only 20 percent. However, individuals who are mildly or moderately deficient in the production of the lactase enzyme may not exhibit symptoms of lactose intolerance.

Causes and symptoms

Lactose intolerance can be caused by some diseases of the digestive system (for example, celiac sprue and gastroenteritis) and by injuries to the small intestine that result in a decreased production of lactase. While rare, some children are also born unable to produce the enzyme. For most people, however, lactase deficiency develops naturally because, after about two years of age, the body produces less lactase. Before humans became dairy farmers, they usually did not continue to drink milk, so their bodies did not produce lactase after early childhood.

Symptoms of lactose intolerance include nausea, cramps, diarrhea, floating and foul-smelling stools, bloating, and intestinal gas. The symptoms usually occur between 30 minutes to two hours after eating or drinking lactose-containing foods. A child may also exhibit weight loss, slow growth, and malnutrition.