Lactoseintolerant

Lactose intolerance, or being lactose intolerant, is the reduced ability to digest lactose, a sugar found in milk and dairy products, due to lower levels of the lactase enzyme in the small intestine. It is not the same as a milk allergy or other food sensitivities.

Most adults worldwide experience primary lactase non-persistence, in which lactase production declines after weaning. Secondary lactose intolerance can arise after illness or injury to the small intestine, such as gastroenteritis, celiac disease, or inflammatory bowel disease. A rare congenital form is present from birth.

Symptoms typically occur after consuming lactose-containing foods and include abdominal pain, bloating, gas, diarrhea, and sometimes nausea. Onset is usually within 30 minutes to several hours.

Diagnosis can involve a hydrogen breath test or a lactose tolerance test, and genetic testing can indicate lactase persistence or non-persistence. Many people also manage symptoms through dietary trial or medical evaluation of other digestive causes.

Management centers on dietary modification. People who are lactose intolerant may limit or avoid dairy, choose lactose-free products, or take lactase enzyme supplements to improve lactose digestion. Adequate calcium and vitamin D from non-dairy or fortified foods are important if dairy is restricted.

Prevalence varies by population, with higher rates of lactase non-persistence in East Asian, Indigenous, and some African and Southern Asian groups, and lower rates in populations with a long history of dairy farming. Across many populations, the majority of adults eventually become lactose intolerant to some degree.