milk [AS, meoluc] , a liquid secreted by the mammary glands or udders of mammalian animals that suckle their young. After weaning, people consume the milk of the cow, as well as that of many other animals, including the goat, camel, mare, reindeer, llama, and yak. Milk is a basic food containing carbohydrate (in the form of lactose); protein (mainly casein, with small amounts of lactalbumin and lactoglobulin); suspended fat; the minerals calcium and phosphorus; and the vitamins A, riboflavin, niacin, thiamine, and, when the milk is fortified, D. Some individuals show a sensitivity reaction to milk caused by a deficiency of the enzyme lactase. See also breast milk.
