DefinitionBy Mayo Clinic Staff
People with lactose intolerance are unable to fully digest the sugar (lactose) in milk. As a result, they have diarrhea, gas and bloating after eating or drinking dairy products. The condition, which is also called lactose malabsorption, is usually harmless, but its symptoms can be uncomfortable.
A deficiency of lactase — an enzyme produced in your small intestine — is usually responsible for lactose intolerance. Many people have low levels of lactase but are able to digest milk products without problems. If you're actually lactose intolerant, though, your lactase deficiency leads to symptoms after you eat dairy foods.
Most people with lactose intolerance can manage the condition without having to give up all dairy foods.
Sept. 02, 2016
- Feldman M, et al. Maldigestion and malabsorption. In: Sleisenger & Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 2016. http://www.clinicalkey.com. Accessed March 26, 2015.
- Leavitt M, et al. Clinical implications of lactose malabsorption versus lactose intolerance. Journal of Clinical Gastroenterology. 2013;47:471.
- Montgomery RK, et al. Lactose intolerance. http://www.uptodate.com/home. Accessed March 25, 2015.
- Lactose intolerance. National Digestive Diseases Information Clearinghouse. http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/. Accessed March 26, 2015.
- Heaney, RP. Dairy intake, dietary adequacy, and lactose intolerance. Advances in Nutrition. 2013;4:151.