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
Pronunciation: LAK-tohs in-TOL-er-uhns

