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What is lactose intolerance?

Lactose intolerance is a condition caused by a lack of an enzyme called lactase, which, in turn, causes the body to be unable to digest lactose, a sugar found in milk and milk products.

Lactase is normally produced by cells lining the small intestine where it breaks down lactose into a form that can be absorbed by the blood. A lack of lactase can cause uncomfortable symptoms for some people. Those who exhibit symptoms are said to be lactose intolerant.

Symptoms

The following are the most common symptoms of lactose intolerance. However, each individual may experience symptoms differently. Symptoms begin to appear in Caucasian children after age five, and in African-American children by two years of age.

Common symptoms, which begin about 30 minutes to two hours after consuming foods or beverages containing lactose, may include:

  • Nausea
  • Cramps
  • Bloating
  • Abdominal pain
  • Gas
  • Diarrhea

The severity of symptoms varies depending on the amount of lactose consumed and the amount each individual can tolerate.

The symptoms of lactose intolerance may resemble other medical conditions or problems. Always consult your doctor for a diagnosis.

Causes

Digestive diseases or injuries to the small intestine can reduce the amount of enzymes produced, and is the usual cause of lactose intolerance in young children. However, most cases of lactose intolerance develop over a period of many years in adults.

How common is it?

Between 30 and 50 million Americans (adults and children) are lactose intolerant. The disorder affects some populations more than others:

  • Seventy-five percent of all African-American, Jewish, Mexican-American, and Native American adults are lactose intolerant.
  • Ninety percent of Asian-American adults are lactose intolerant.
  • Lactose intolerance is least common among people with a northern European heritage.
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