Lactose intolerant people have problems when they consume dairy products because they lack sufficient amounts of an enzyme called lactase. Lactase is responsible for breaking down lactose, which is the primary sugar found in milk and dairy products, into simpler sugars called glucose and galactose. These simpler sugars can then be absorbed and used by the body for energy.
In lactose intolerant individuals, the level of lactase in the small intestine is significantly reduced or absent. As a result, when they consume dairy products, the undigested lactose moves to the large intestine, where it is fermented by gut bacteria. This fermentation process produces gas and certain acids, leading to symptoms such as bloating, gas, abdominal pain, diarrhea, and sometimes nausea.
I hope this helped!
~~~Harsha~~~