Lactose is a type of sugar found naturally in milk and dairy products like cheese, yogurt, and ice cream. It's what gives milk its slightly sweet taste, though you might not notice it because lactose isn't nearly as sweet as table sugar.

Your body breaks down lactose using a special enzyme called lactase. But some people's bodies don't make enough lactase, a condition called lactose intolerance. When lactose-intolerant people drink regular milk, they might get stomachaches, feel bloated, or experience other uncomfortable symptoms because their bodies can't properly digest the lactose.

Scientists can now remove lactose from milk to create lactose-free milk that tastes almost exactly like regular milk but won't bother people who are lactose intolerant. Some people also take lactase pills before eating dairy to help their bodies handle the lactose.

Baby mammals, including human babies, rely on the lactose in their mother's milk for energy and growth. In fact, human breast milk contains more lactose than cow's milk does.