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Lactose Intolerance - Definition of Lactose Intolerance

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Updated December 22, 2008

Definition: Lactose intolerance is the inability to digest significant amounts of lactose, the major sugar found in milk. Lactose intolerance is caused by a shortage of the enzyme lactase, which is produced by the cells that line the small intestine. Lactase breaks down milk sugar into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream. Symptoms of lactose intolerance include:
  • Nausea
  • Cramps
  • Bloating
  • Gas
  • Diarrhea
Symptoms begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of symptoms depends on many factors, including the amount of lactose a person can tolerate and a person’s age, ethnicity, and digestion rate.
Pronunciation: LAK-tohs in-TOL-er-uhns
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