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Definition
By Mayo Clinic staffLactose intolerance, also called lactase deficiency, means you aren't able to fully digest the milk sugar (lactose) in dairy products. It's not usually dangerous, but symptoms of lactose intolerance can be uncomfortable enough to steer you clear of the dairy aisles.
The problem behind lactose intolerance is a deficiency of lactase — an enzyme produced by the lining of your small intestine. Some people who think they are lactose intolerant actually don't have impaired lactose digestion. And not everyone with low levels of lactase is lactose intolerant. Only people with low lactase levels and symptoms are considered to have lactose intolerance.
You can control symptoms of lactose intolerance through a carefully chosen diet that limits lactose without cutting out calcium, and possibly by taking supplements.
Symptoms
