Dairy milk is an opaque white
liquid produced by the
mammary glands
of
mammals (including
monotremes). It
provides the primary source of nutrition for newborn mammals before they
are able to
digest other types of food. The early
lactation milk is known as
colostrum, and
carries the mother's
antibodies to the baby. It can reduce the risk of
many diseases in the baby. The exact components of raw milk varies by
species, but it contains significant amounts of
saturated fat,
protein and
calcium as well as
vitamin
C. Cow's milk has a
pH ranging from 6.4 to 6.8, making it slightly
acidic
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 derived from other animals.
Nutrition for infant mammals
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 currently, continue to use breast
milk to feed their children until they are 7 years old.[3]
Food product for humans
In many cultures of the world, especially the Western world, humans
continue to consume milk beyond infancy, using the milk of other animals
(in particular, cows) as a food product. For millennia, cow 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.
Industrial science has brought us 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. Most humans[citation
needed] lose the ability to fully digest milk
after childhood (that is, they become lactose intolerant). 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. [4] On the other
hand, those groups that do continue to tolerate milk often have exercised
great creativity in using the milk of domesticated ungulates, not only of cows, but also
sheep, goats, yaks, water buffalo, horses, and camels