Lactase is an enzyme. Like other enzymes, it is needed for a specific biochemical reaction in the body. The biochemical reaction that involves lactase breaks down lactose, a sugar in milk and milk products. Some people’s bodies do not make enough lactase, so they are not able to digest milk well. They can take supplemental lactase to help them break down lactose and tolerate milk. In these people lactase can prevent symptoms of lactose intolerance including cramps, diarrhea, and gas.
Lactase’s function is to break down lactose into the two simple sugars it is made up of, glucose and galactose. Breaking down lactose into its simple sugars makes it possible for it to be absorbed via the small intestine and used by the body. If lactose is not broken down, it will pass through the digestive tract without being absorbed.