Hello. Some people will have abdominal distension, abdominal sound and even diarrhea (commonly known as gastrointestinal discomfort) after drinking milk, because these people have lactose intolerance. It is rare for people who drink milk regularly. What is lactose intolerance? Milk is rich in lactose, generally between 4.5-5.2%, which varies with different regions, feeds and varieties. After people eat milk, lactose needs to be decomposed into glucose and galactose by lactase in the human body before it can be absorbed. Some people have less lactase and can't decompose and absorb lactose. Results Lactose enters the back end of the intestine and is fermented by bacteria in the intestine to produce acid and gas, which is lactose intolerance.