Lactase deficiency

Not enough of an enzyme called lactase in the small intestine to digest lactose, a prominent component of milk and most other dairy products. Lactose is sometimes also used as an ingredient in other foods, so anyone with lactase deficiency should check food labels with care. Most people are born with the ability to make adequate amounts of lactase, but lactase production tends normally to go down with age, more so in some persons than others. There are significant differences in lactase production among different ethnic groups. Inadequate lactase production can cause difficulty digesting lactose-containing products, which include dairy products themselves and any foods containing dairy products as ingredients. The most common symptoms of lactase deficiency are diarrhea, bloating, and gas. The diagnosis of lactase deficiency may be made by a trial of a lactose-free diet or by special testing.

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lac·tase de·fi·cien·cy (lakґtās) the most common disaccharidase deficiency, reduced or absent lactase activity in the intestinal mucosa, usually due to an inherited defect in the enzyme but sometimes secondary to disorders involving the small intestinal mucosa. The hereditary adult form, an autosomal recessive trait, is the normal state in most populations other than white Northern Europeans and may be characterized by abdominal pain, flatulence, and diarrhea after ingestion of milk (lactose intolerance); the rare hereditary congenital form (congenital lactose intolerance), an autosomal recessive trait, is characterized by diarrhea, vomiting, and failure to thrive.