How common is lactose malabsorption?

Lactose insufficiency is very rarely seen in infants and young children. However, up to 90 percent of adults have some degree of lactose malabsorption, particularly those of African, Jewish, Native-American, Mexican and Asian descent. In parts of the world (especially northern Europe) where the climate allows dairy cows to be raised, milk and milk products are a major part of the economy and cuisine. Interestingly, people descended from northern Europe tend to retain the ability to digest lactose into adulthood, at least to some degree.