Misselwitz B; Fox M. - - Lancet Gastroenterol Hepatol 2017; in press

What is normal and abnormal in lactose digestion?

Variations in lactose metabolism continue to fascinate patients, clinicians, geneticists, and anthropologists.1 In the small intestine of all healthy newborns, the lactose-digesting enzyme lactase is abundant. However, in most people lactase expression is strongly reduced after infancy (ie, lactase non-persistence), resulting in a limited ability to digest lactose after childhood.