Lactase is an enzyme that breaks down lactose, the sugar of milk, into the simpler sugars glucose and galactose.

Lactase enzymes are given to persons who suffer from lactose intolerance but who must or wish to continue the consumption of milk for a variety of reasons. The number of people who are lactose intolerant in various populations ranges from 3-8 percent in the Scandinavian countries, to over 95 percent in Asia.