When to suspect lactose intolerance. Symptomatic, ethnic, and laboratory clues.

Lactose intolerance is widespread, with adult-type hypolactasia being the predominant cause of lactose malabsorption. Daily ingestion of less than 240 mL of milk is well tolerated by most lactose-intolerant adults. Some persons with normal lactase activity may become symptomatic on consumption of products containing lactose. Lactose maldigestion may coexist in adults with irritable bowel syndrome and in children with recurrent abdominal pain. Management consists primarily of dietary changes. People who avoid dairy products should receive calcium supplementation and should be advised to read ingredient labels carefully. Several lactase replacement products are available, but their efficacy varies.