Lactose is a type of sugar found in milk and other dairy products. Lactose intolerance develops when the small intestine does not make enough of an enzyme called lactase. The body needs this enzyme to digest lactose.
Lactase deficiency; Milk intolerance; Disaccharidase deficiency; Dairy product intolerance
Babies' bodies make the lactase enzyme so they can digest milk, including breast milk.
Babies born too early (premature) sometimes have lactose intolerance. Children who were born at full term usually do not show signs of the problem until they are at least 3 years old.
Lactose intolerance is very common in adults. It is rarely dangerous. Around 30 million American adults have some degree of lactose intolerance by age 20.
Other causes of lactose intolerance include:
Symptoms often occur 30 minutes to 2 hours after having milk products. Large doses of milk products may cause worse
Exams and Tests
Other intestinal problems, such as irritable bowel syndrome, may cause the same symptoms as lactose intolerance.
Tests to help diagnose lactose intolerance include:
Cutting down or removing milk products from your diet usually eases symptoms.
Most people with low lactase levels can drink 2 - 4 ounces of milk at one time (up to one-half cup) without having symptoms. Larger (more than 8 oz.) servings may cause problems for people with lactase deficiency.
Milk products may be easier to digest include:
You can add lactase enzymes to regular milk, or take these enzymes in capsule or chewable tablet form.
Not having milk in your diet can lead to a shortage of calcium, vitamin D, riboflavin, and protein. You need
Read food labels. Lactose is also found in some non-milk products -- including some beers.
Symptoms usually go away after removing milk products and other lactose containing products from your diet. Infants or children may have slow growth or weight loss without a change in diet.
When to Contact a Medical Professional
Call your health care provider if:
There is no known way to prevent lactose intolerance. You can prevent symptoms by avoiding foods with lactose. Read food labels carefully. Lactose is also found in some non-milk products, including some beers.
Hogenauer C, Hammer HF. Maldigestion and malabsorption. In: Feldman M, Friedman LS, Sleisenger MH, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2010: chap 101.
Lactose intolerance. The National Digestive Diseases Information Clearinghouse (NDDIC). NIH Publication No. 09-2751. June 2009, updated April 12, 2012.
Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 142.