What is lactose intolerance primarily caused by?

Lactose intolerance is primarily caused by a deficiency of the lactase enzyme. Lactase is an enzyme produced in the small intestine that is responsible for breaking down lactose, a sugar found in milk and dairy products, into glucose and galactose, which can be easily absorbed by the body. In individuals with lactose intolerance, there is insufficient lactase activity, leading to the inability to adequately digest lactose.

When lactose is not properly digested, it passes into the colon, where it is fermented by gut bacteria, resulting in symptoms such as bloating, gas, diarrhea, and abdominal pain. This condition can arise due to a natural decrease in lactase production as people age or as a result of certain medical conditions that affect the intestinal lining.

While genetic mutations can play a role in how much lactase an individual produces, the immediate cause of lactose intolerance is the deficiency of the lactase enzyme itself. Excess intake of sugars or high-fat foods does not directly lead to lactose intolerance, although dietary choices may influence symptoms in some individuals.