Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many diseases in the baby. It also contains many other nutrients.[1] As an agricultural product, milk is extracted from mammals and used as food for humans. Worldwide, dairy farms produced about 730 million tonnes of milk in 2011.[2] India is the world's largest producer and consumer of milk, yet neither exports nor imports milk. New Zealand, the European Union's 27 member states, Australia, and the United States are the world's largest exporters of milk and milk products. China and Russia are the world's largest importers of milk and milk products.[3][4] Throughout the world, there are more than 6 billion consumers of milk and milk products. Over 750 million people live within dairy farming households. Milk is a key contributor to improving nutrition and food security particularly in developing countries. Improvements in livestock and dairy technology offer significant promise in reducing poverty and malnutrition in the world. There are two distinct types of milk consumption: a natural source of nutrition for all infant mammals and a food product for humans of all ages that is derived from other animals. Nutrition for infant mammals A human baby feeding on its mother's milk A goat kid feeding on its mother's milk In almost all mammals, milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. Some cultures, historically or cur ently, continue to use breast milk to feed their children until they are seven years old.[citation needed] Human infants sometimes are fed fresh goat milk. There are known risks in this practice, including those of developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia, and a host of allergic reactions.[6] Food product for humans Holstein cattle, the dominant breed in industrialized dairying today In many cultures of the world, especially the Western world, humans continue to consume milk beyond infancy, using the milk of other animals (especially cattle, goats and sheep) as a food product. For millennia, cow's milk has been processed into dairy products such as cream, butter, yogurt, kefir, ice cream, and especially the more durable and easily transportable product, cheese. Modern industrial processes produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products. Humans are an exception in the natural world for consuming milk past infancy, despite the fact that most adult humans show some degree of lactose intolerance.[7] The sugar lactose is found only in milk, forsythia flowers, and a few tropical shrubs. The enzyme needed to digest lactose, lactase, reaches its highest levels in the small intestines after birth and then begins a slow decline unless milk is consumed regularly.[8] On the other hand, those groups who do continue to tolerate milk often have exercised great creativity in using the milk of domesticated ungulates, not only of cattle, but also sheep, goats, yaks, water buffalo, horses, reindeers and camels. The largest producer and consumer of cattle and buffalo milk in the world is India