Babies have a sucking reflex that enables them to suck and swallow milk. It is possible for most mothers to nourish their infant (or infants in the case of twins and multiple births) by breastfeeding for the first six months, if not longer, without the supplement of infant formula milk or solid food.



In most situations human breast milk is the best source of nourishment for human infants, preventing disease, promoting health and reducing health care costs (exceptions include situations where the mother is taking certain drugs or is infected with tuberculosis or HIV).

Experts disagree about how long to breastfeed to gain the greatest benefit, and about the risks of using artificial formulas. In both developing and developed countries, artificial feeding is associated with more deaths from diarrhoea in infants.

The World Health Organization recommends a minimum of two years of breastfeeding and exclusive breastfeeding for the first six months of life. AAP recommends at least one year of breastfeeding and exclusive breastfeeding for the first six months of life. Exclusive breastfeeding for the first six months of life "provides continuing protection against diarrhea and respiratory tract infection" that is more common in babies fed formula.

The World Health Organization (WHO)and American Academy of Pediatrics (AAP)both stress the value of breastfeeding for mothers and children. While recognizing the superiority of breastfeeding, regulating authorities work to make artificial feeding safer when it is not used.

The primary function of mammary glands is to nurture young by producing breast milk. The production of milk is called lactation. (While the mammary glands that produce milk are present in the male, they normally remain undeveloped.)

The orb-like shape of breasts may help limit heat loss, as a fairly high temperature is required for the production of milk. Alternatively, one theory states that the shape of the human breast evolved in order to prevent infants from suffocating while feeding.

Since human infants do not have a protruding jaw like human evolutionary ancestors and other primates, the infants nose might be blocked by a flat female chest while feeding.[8] According to this theory, as the human jaw receded, the breasts became larger to compensate.

Milk production unrelated to pregnancy can also occur. This galactorrhea may be an adverse effect of some medicinal drugs (such as some antipsychotic medication), extreme physical stress or endocrine disorders. If it occurs in men it is called male lactation.

Newborn babies are often capable of lactation because they receive the hormones prolactin and oxytocin via the mother's bloodstream, filtered through the placenta. This neonatal liquid is known colloquially as witch's milk.

Not all the properties of breast milk are understood, but its nutrient content is relatively stable. Breast milk is made from the nutrients in the mother's bloodstream and bodily stores. Some studies estimate that a woman who breastfeeds her infant exclusively uses 400 to 600 extra calories a day in producing milk. The composition of breast milk depends on how long the baby nurses.

Research shows that the milk and energy content of breastmilk actually decreases after the first year. Breastmilk adapts to a toddler's developing system, providing exactly the right amount of nutrition at exactly the right time.