Breast milk: Milk from the breast. Human milk contains a balance of nutrients that closely matches infant requirements for brain development, growth and a healthy immune system. Human milk also contains immunologic agents and other compounds that act against viruses, bacteria, and parasites. Since an infant's immune system is not fully developed until age 2, human milk provides a distinct advantage over formula.
Children who are breastfed enjoy lower rates of several chronic childhood diseases, including respiratory infections and ear infections as well as diarrhea. Breastfed infants gain less weight and tend to be leaner at 1 year of age than formula-fed infants, resulting in fewer overweight and obese children.
Breastfeeding releases a hormone in a woman's body that causes her uterus to return to its normal size and shape more quickly and reduces blood loss after delivery. In addition, breastfeeding for longer periods of time (up to 2 years) and among younger mothers may possibly reduce the risks of breast and ovarian cancers.