by Debra Wood, RN
Lactose intolerance is gastrointestinal upset related to the inability to digest significant quantities of lactose. Lactose is a sugar found in milk and other dairy products.
Lactose intolerance is caused by a reduction in the digestive enzyme lactase. Lactase breaks down the sugar lactose into sugars that can be more easily absorbed. When not fully broken down, lactose ferments in the colon and causes symptoms.
Some people are born unable to make lactase. Others develop the intolerance over time.
Risk Factors TOP
Factors that may increase your chances of lactose intolerance:
Symptoms of lactose intolerance generally begin within 2 hours of consuming milk or other dairy products. The severity of symptoms depends on how much lactase your body produces and how much lactose you eat.
Lactose intolerance may cause:
The doctor will ask about your symptoms and medical history. A physical exam will be done. Your doctor may recommend a trial period of eating no milk or milk products to see if symptoms resolve.
Your doctor may want to perform tests to help make the diagnosis. These may include:
Your doctor may recommend a biopsy to examine intestinal tissue.
Temporary lactose intolerance following an infection usually goes away after the intestine heals.
Treatment for chronic lactose intolerance focuses on managing symptoms. For most people, removing dietary lactose, especially in children and adolescents, would not be recommended. Milk and milk products provide sources of calcium and other food elements that are hard to replace. If complete elimination is chosen, then careful replacement of calcium is needed for good health.
Keep a food diary of what you eat and what the reaction is. Discuss the findings with your doctor or a dietitian.
Dietary changes may include:
Your doctor may recommend lactase enzymes if you can tolerate only small quantities of lactose. The enzyme supplements come in liquid and chewable form. A few drops of the liquid added to milk, which is allowed to sit overnight, can decrease the amount of lactose in the milk. Tablets are chewed or swallowed before eating foods that contain lactose.
There are no current guidelines to prevent lactose intolerance.
American College of Gastroenterology
American Gastroenterological Association
Canadian Association of Gastroenterology
Dietitians of Canada
Heyman MB. Lactose intolerance in infants, children, and adolescents. Pediatrics. 2006;118(3):1279-1286.
Lactose intolerance. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: https://www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance. Updated June 2014. Accessed October 3, 2017.
Lactose intolerance in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed... . Updated November 17, 2016. Accessed October 3, 2017.
Lactose intolerance in children. EBSCO DynaMed Plus website. Available at: http://www.dynamed... . Updated June 22, 2016. Accessed October 3, 2017.
Montalta M, Curigliano V, Santoro L, et al. Management and treatment of lactose malabsorption. World J Gastroenterol. 2006;12(2):187-191.
National Institutes of Health. National Institutes of Health (NIH) 2010 consensus development conference statement on lactose intolerance and health. 2010;22-24;27(2).
Understanding food allergies and intolerances. American Gastroenterological Association website. Available at:
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Updated September 2017. Accessed October 3, 2017.
Last reviewed September 2018 by EBSCO Medical Review Board Daus Mahnke, MD
Last Updated: 12/31/2013
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