Lactose Intolerance

What is Lactose Intolerance? Lactose intolerance is the inability to break down lactose from dairy due to an insufficiency of the enzyme lactase in the brush border of the small intestine.

What Causes Lactose Intolerance?

Lactose intolerance can be caused by three possible mechanisms:

  • Primary lactase deficiency is a rare, autosomal recessive condition that causes a congenital deficiency in lactase.
  • Secondary lactase deficiency is the most common cause of lactose intolerance. It is a temporary condition caused by transient damage to the villi of the GI tract in children from infections, commonly from rotavirus and giardia. Secondary deficiency may also be caused by intestinal inflammation from Celiac disease, IBD, and medications.
  • Acquired lactase deficiency is the result of a normal age-related decrease in the lactase found in the intestine. 

Symptoms of Lactose Intolerance

Lactose intolerance can cause a variety of gastrointestinal symptoms and distress in response to the ingestion of lactose containing products, including:

  • Abdominal cramping or pain
  • Bloating
  • Stomach gas
  • Watery diarrhea
  • Hyperactive bowel sounds
  • Flatulence

Source: Lactose Intolerance. (2021, October 25). American College of Gastroenterology. Retrieved May 19, 2022, from