Chapter 13-8: Lactose Intolerance

TEXTBOOK PRESENTATION

Lactose intolerance commonly presents with symptoms of belching, bloating, flatulence, and diarrhea. Though usually chronic, the symptoms may be acute or subacute in the setting of recent infection or dietary changes. Symptoms are associated with intake of milk or milk-containing products.

DISEASE HIGHLIGHTS

1. Lactase is the enzyme that metabolizes lactose.

   1. Rarely, it can be deficient at birth.

   2. More commonly, it can become deficient with age.

2. It is thought that some ethnicities evolved persistent lactase activity because of the importance of milk products as a calorie source in their environments.

3. Lactose intolerance can be caused by lactase deficiency or lactose malabsorption.

   1. Acquired lactase deficiency is most common in people of Asian, African, Middle East, Mediterranean, and Native American ancestry.

   2. Secondary lactose malabsorption can occur in the setting of underlying bowel diseases, small intestinal bacterial overgrowth, and infection of the small bowel. This process is more common in people with low levels of lactase activity at baseline.

Lactose intolerance after episodes of gastroenteritis has been reported as high as 50-70% but frequency depends on patient ethnicity.

4. Milk, ice cream, and yogurt have the highest levels of lactose.

5. Foods with high lactose and low fat (skim milk) tend to cause the most symptoms as these foods deliver lactose to the small intestine the fastest.

EVIDENCE-BASED DIAGNOSIS

1. The diagnosis of lactose intolerance is made clinically based on a consistent history and resolution of symptoms on a lactose-free diet.

2. More definitive tests, including lactose tolerance test or lactose breath hydrogen test, can be performed in patients in whom the diagnosis is likely but not clear historically.

   1. False-negative testing can occur in setting of recent antibiotic use.

   2. False-positive testing can occur in the setting of small intestinal bacterial overgrowth.

TREATMENT

1. Lactose intolerance is treated by decreasing lactose intake.

2. Enzyme supplementation with lactase is often helpful in patients with chronic symptoms.

3. In post-gastroenteritis lactose malabsorption, lactase activity will eventually recover when the intestinal brush border regenerates.

4. Because of the high prevalence of mild lactose intolerance and the frequent exacerbation following gastroenteritis, patients with acute gastroenteritis should be advised to avoid dairy products for 2 weeks after recovery.