What is lactose intolerance primarily caused by?

Lactose intolerance is primarily caused by a deficiency in the lactase enzyme, which is responsible for breaking down lactose, the sugar found in milk and dairy products. In individuals with lactose intolerance, the small intestine produces insufficient amounts of lactase, leading to the inability to properly digest lactose. As a result, undigested lactose travels to the colon, where it is fermented by bacteria, leading to symptoms such as bloating, gas, diarrhea, and abdominal pain.

The other factors mentioned, such as excessive consumption of dairy products, increased bile production, or high levels of stomach acid, are not the underlying causes of lactose intolerance. While excessive consumption of dairy might exacerbate symptoms in someone who is lactose intolerant, it does not initiate the condition itself, which is fundamentally linked to the deficient production of the lactase enzyme.