Lactose intolerance is the inability to digest lactose, one of the two most common sugars in the human diet, and the primary sugar in cow’s milk. Variable amounts of it are found in many products (such as cheese, ice cream, and yogurt) that are derived from milk. Lactose intolerance occurs when there is a deficiency of the enzyme lactase, which is necessary to convert lactose into simpler sugars that can be absorbed into the bloodstream.
An affected person who consumes foods containing lactose may develop bloating, cramping, diarrhea, in-creased bowel gas, and general abdominal discomfort. This type of reaction to lactose may be a lifelong tendency or a temporary problem. Lactose intolerance is very common in both African-Americans and Asians after the age of five. Because lactase is found in the outer cell layer of the small intestine, it may also be lost temporarily during infections or other disorders that damage the intestinal lining. After a child has had gastro-enteritis (stomach flu), intestinal lactase may be reduced for days or even weeks; it is sometimes recommended that milk products be avoided for several days after a child has had this type of infection.
Avoidance of foods containing lactose will prevent symptoms in a child with lactose intolerance. In addition, nonprescription lactase preparations (Lactaid, Lactrase, and others) may be added to milk products or swallowed along with lactose-containing foods to prevent symptoms.