The true number of people with lactose intolerance is not known. Many people who have symptoms of lactose intolerance have not been diagnosed with the condition. Many people who think they are lactose intolerant do not have difficulty digesting lactose. Many people who have difficulty digesting lactose do not get symptoms.1
Lactose intolerance can affect anyone. In the United States, it is most common among1:
Lactose intolerance is uncommon in young children because most infants are born with enough lactase. But for many people, the amount of lactase in their bodies decreases over a lifetime.
Preterm infants born before 34 weeks' gestation can have low lactase levels because their digestive tract is not fully developed.2
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