lactose

Somewhat less than 40% of people in the world retain the ability to digest lactose after childhood.

全世界大约不到40%的成年人能够在童年过后保留消化乳糖的能力。

Some people have trouble digesting lactose, a carbohydrate in milk and milk products, because of the deficiency of enzyme lactase in the body.

有些人无法消化乳糖，一种在牛奶和奶制品中的碳水化合物，这是因为在他们的身体中缺少乳糖消化酶。

Though children were able to drink milk, they typically developed lactose intolerance as they grew up.

虽然小孩喝牛奶没有问题，但在长大后他们通常都会产生乳糖不耐受。