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Lactose Intolerance: A Common Problem

The AAP provides an updated and revised statement.

Lactose intolerance is a clinical syndrome defined as the occurrence of one or more symptoms related to the gastrointestinal tract (e.g., abdominal pain or diarrhea) after ingestion of lactose-containing foods. Both primary lactase deficiency and secondary lactase deficiency can result in lactose intolerance. Congenital lactase deficiency is rare. The AAP recently released a clinical report about lactose intolerance. Highlights of the report include:

• Primary lactase deficiency, the most common cause of lactose intolerance, is caused by the absence of lactase and affects 70% of the world’s population. The prevalence and age of onset vary by ethnicity; it is particularly common in Hispanic, black, Asian, American Indian, and Ashkenazi Jewish people. Primary lactose intolerance develops in childhood but is rare in children younger than 3 years.
  
• Secondary lactase deficiency is caused by small bowel injury, such as acute gastroenteritis. Only very young infants (younger than 3 months) and malnourished children require a lactose-free diet. Giardia often leads to lactose intolerance.
  
• To confirm diagnosis, a lactose-free diet may be tried for 2 weeks. In children who are lactose intolerant, symptoms should resolve and then reappear with the reintroduction of dairy products. Families should be aware of hidden sources of lactose, such as bread, salad dressings, candies, pancakes, and baked goods.
  
• Formal diagnostic testing, such as the hydrogen breath test or testing for fecal-reducing substances, is rarely necessary.
  
• The degree of lactase deficiency, and consequently the amount of lactose tolerability, varies by child. Partially digested products, including cheese, yogurt, and pretreated milk, make treatment easier.
  
• Diets of children who are lactose intolerant should include a good source of calcium because of recent evidence indicating that lactose enhances calcium absorption and its absence might lead to inadequate bone mineral content.
  

Comment: Although helpful, this AAP summary statement is not a formal practice guideline because it is not based on a systematic review of the literature. Lactose intolerance should not be confused with cow’s milk protein sensitivity — they are entirely different entities. In contrast with primary lactose intolerance, cow’s milk protein allergy affects young infants and usually resolves during the first year. This distinction is important when considering changes in diet, including formula. Although there are many hidden sources of lactose, most older children can tolerate some amount. The lactose content of foods can range from about 12 g for 8 ounces of cow’s milk to 1g for 1 ounce of Swiss cheese (a sample list of lactose content in selected foods is available).

— Howard Bauchner, MD

Published in Journal Watch Pediatrics and Adolescent Medicine January 3, 2007

Citation(s):

Heyman MB for the Committee on Nutrition. Lactose intolerance in infants, children, and adolescents. Pediatrics 2006 Sep; 118:1279-86.

• Original article (Subscription may be required)
• Medline abstract (Free)