[Lactose and its implications in gastroenterology. Nutrition and food sciences]

The development of the practice of dairying allowed humans to become the only species of mammals to consume milk after the time of weaning. Milk contains the sugar, lactose, which requires the enzyme, intestinal lactase, to digest. Adult mammals do not retain ordinarily express this enzyme after early life, but through evolution, some groups of humans-notably those who practice dairying-have evolved to have the persistence of lactase into adulthood. In Meso-America, South America, Asia and most of Africa, the majority of individuals are genetically lactase non-persistent. With milk as an element of the diet, this human polymorphism for lactase produced its implication in gastroenterology, nutrition and food sciences for both those who can digest and those who cannot digest this sugar. Here, we review the issues of terminology, molecular genetics, diagnosis, health consequences, and management of different lactase states at a general and generic level.