Milk is produced by mammals to feed their young. It is a white liquid produced in the mammary glands and provides the neonate with fats and proteins, calcium and Vitamin C necessary for development, as well as transferring the mother’s antibodies to the young for protection against disease.

With a sense that this is an invaluable food, man has historically drunk milk beyond infancy, most usually in the form of milk from other species, predominantly cows and goats and sheep. Other creatures from which milk is taken include reindeer in the north, buffalo in India and other parts of Asia and Africa, horse, yaks in the northern tundra and camels in the deserts of Arabia. Milk has also traditionally been processed into cheese, butter, soured creams and milks and yoghurt. Some of these permit a way of preserving milk to consume at times of year when it may not have been readily available.

Lactase, the enzyme required to digest milk, declines after infancy and Asian and African peoples are inclined to have lactose intolerance.