Lactase Deficiency

Key Features

• Partial to complete lactose intolerance affects ~50 million people in the United States

• Occurs in 90% of Asian Americans, 70% of African Americans, 95% of Native Americans, 50% of Mexican Americans, 60% of Jewish Americans, < 25% of White adults

• Also occurs secondary to Crohn disease, celiac disease, viral gastroenteritis, giardiasis, short bowel syndrome, malnutrition

Clinical Findings

• Bloating, abdominal cramps, and flatulence with mild to moderate amounts of lactose malabsorption

• Diarrhea

• Differential diagnosis

  • Inflammatory bowel disease

  • Mucosal malabsorptive disorders

  • Irritable bowel syndrome

  • Pancreatic insufficiency

Diagnosis

• Diarrheal stool specimens have an increased osmotic gap and pH < 6.0

• Hydrogen breath test: After ingestion of 50 g lactose, a rise in breath hydrogen of > 20 ppm within 90 minutes is a positive test

• Empiric trial of a lactose-free diet for 2 weeks leads to resolution of symptoms

Treatment

• Eliminate or restrict milk products

• Spread dairy product intake throughout the day

• Use lactase enzyme supplements (eg, nonprescription formulation [Lactaid]) when ingesting dairy products

• Calcium supplementation: calcium carbonate 500 mg orally two to three times daily