Who is affected by lactose intolerance

Lactose intolerance is very common—approximately 50 million people in the United States have the condition.1 Worldwide, 70% of adults have some degree of lactose intolerance.2

Lactose intolerance occurs more often in Native Americans and people of Asian, African, and South American descent than among people of European descent. Experts believe that lactose intolerance is directly related to how long ago a person's ancestors were introduced to dairy products.


  1. McQuaid KR (2008). Lactase deficiency section of Gastrointestinal disorders. In SJ McPhee et al., eds., Current Medical Diagnosis and Treatment 2008, 47th ed., pp. 533–534. New York: McGraw-Hill.
  2. Beyer PL (2008). Lactose maldigestion or lactose intolerance section of Medical nutrition therapy for lower gastrointestinal tract disorders. In LK Mahan, S Escott-Stump, eds., Krause's Food and Nutrition Therapy, 12th ed., pp. 687–689. St. Louis: Saunders Elsevier.

Last Updated: August 3, 2009

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