Where in the the gastrointestinal tract do you usually digest lactose and why is the pain in a different location from where lactose would be digested?

Lactose is primarily digested in the small intestine, where the enzyme lactase breaks it down into glucose and galactose. However, if an individual is lactose intolerant, undigested lactose can reach the colon, leading to fermentation by gut bacteria and the production of gas and acids, which can cause pain and discomfort. This pain often occurs in the lower abdominal area, as opposed to the upper small intestine where digestion takes place, due to the accumulation of gas and irritation in the colon.