Lactase persistence

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Lactase persistence or lactose tolerance is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk. In most mammals, the activity of the enzyme is dramatically reduced after weaning.^[1] In some human populations though, lactase persistence has recently evolved^[2] as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy. Lactase persistence is very high among northern Europeans, especially Irish people. Worldwide, most people are lactase non-persistent,^[1] and are affected by varying degrees of lactose intolerance as adults. However, lactase persistence and lactose intolerance can overlap.