Lactose intolerance is the body’s inability to digest lactose, due to the lack of lactase in the small intestine. When someone has lactase deficiency, lactose can’t be digested and remains in the digestive system causing a wide range of intestinal distress symptoms, including abdominal pain and cramping, gas, diarrhea and bloated stomach.
Basically, whenever you eat, your body has to process the food. Its ability to digest and absorb all the nutrients (or not) depends on your genetic code. In humans, lactase is encoded by the LCT gene, essential for lactose digestion. LCT gene is responsible for the production of the lactase enzyme, that is expressed in the enterocyte, lying in the small intestine, which helps us breakdown and absorb lactose.