Lactase Persistence

The Ability to Digest Milk

All infant mammals drink milk. But you may have friends who don’t drink milk, because it gives them stomach cramps or diarrhea.

They may be lactose intolerant, which means they cannot digest lactose, the sugar in milk.

A man with a sad face and a crossed-out gallon of milk labeled Lactose Intolerant and a woman with a happy face and a gallon of milk labeled Lactose tolerant.
Lactose intolerant can't digest milk. Lactose tolerant can digest milk.