Breast milk is the most complete single source of nutrition for the first 6 months of life. There is no formula that duplicates breast milk. Breast milk contains:

• Antibodies and living cells that help protect the infant from infections. They also promote healthy bacteria that help the intestines to digest nutrients properly.
• Essential vitamins and minerals for optimal growth and development.
• Proteins, fats, and other substances that are especially adapted for the needs of a growing baby.

Breast milk changes over time with a baby's nutritional needs. The first milk produced is colostrum, a sticky, yellowish liquid that contains protein, minerals, vitamins, and antibodies. Colostrum is produced during pregnancy and the first few days after delivery. The transitional milk comes in after the colostrum, followed by mature milk about 10 to 15 days after you deliver your baby.

Breast milk also changes during each feeding. The last milk in the breast, called hindmilk, is higher in calories, nutrients, and fat and helps satisfy your baby's appetite. To get to the hindmilk, breast-feeding (or pumping) should continue on one breast until it is emptied. This usually requires at least 10 to 20 minutes of feeding or pumping for each breast.

Breast milk is easy to digest, so breast-fed babies are rarely constipated. Newborns younger than 2 weeks should have at least 1 or 2 bowel movements a day. Babies older than 2 weeks can go 2 days and sometimes longer between bowel movements. It’s usually okay if it takes longer than 2 days, especially if your baby is feeding well and seems comfortable.

Breast-feeding protects and helps your baby in ways that formula feeding does not. These benefits include:

• Fewer upper respiratory infections (such as colds), ear infections, and lower respiratory infections (such as pneumonia). Breast milk has more than 50 components that boost the immune system and help protect your baby. When illnesses occur, they tend to be shorter and less severe. Fresh breast milk offers the highest concentration of protective antibodies.¹
• A reduced risk for developing certain conditions, like diabetes, asthma, and high cholesterol.²
• Fewer gastrointestinal illnesses (vomiting and diarrhea).
• Reduced risk for obesity. Breast-fed babies are less likely than formula-fed babies to be overweight later in infancy and during childhood and adolescence.² Maintaining a healthy weight reduces the risk for certain conditions, such as diabetes.
• Possibly, a lower risk of food allergies.

Breast-feeding for at least 1 year is recommended by the American Academy of Pediatrics, the American Association of Family Physicians, and the American College of Obstetrics and Gynecology.^{2, 3}

Children younger than one year of age may benefit from a vitamin D supplement. Talk with your doctor about how much and what sources of vitamin D are right for your child in addition to your child's other vitamin and mineral needs, especially iron.