Milk

Milk is an emulsion consisting mainly of water but also containing protein, fat, carbohydrates, vitamins and trace elements.

Tolerance
Unlike other mammals, humans, especially those of European and partly African descent, drink milk after infancy. The ability to digest lactose in milk as an adult is genetically late (about 8,000 years old) and is likely to have arisen from widespread dairy cattle farming in these areas. Lactose is digested by the enzyme lactase, which is produced by everyone in the first months of life, but which most people stop producing after infancy. While most people of European origin tolerate milk, most Asians, Native Americans and Africans suffer from indigestion (bloating, diarrhea) due to lactose intolerance. However, these people may take the missing enzyme in the form of lactase tablets.