Lactase Deficiency: An Example of Dietary Evolution

摘要: The ability to assimilate lactose, a primary constituent of milk, is dependent upon the presence lactase, genetically controlled enzyme in small intestine. In most mammals, levels lactase are high during infancy, but fall rapidly following weaning; adults lactase-deficient. man, some populations, including Orientals, Australian Aborigines, and Negroes, deficient as adults, while others, Nilotic Negroes Europeans, maintain consistently throughout life regardless individual lactose intake. Ingestion even amounts by lactase-deficient individuals usually gives rise variety symptoms, cramps, bloating, diarrhea. It hypothesized that prior domestication animals development dairying, normal condition for all men was adult deficiency, with introduction into diet certain cultures, new selective pressures were created favored genoty...