What’s in breast milk?

What’s in breast milk depends on when it’s being made and for whom. One of the wonderful characteristics of human milk is the way it changes to meet your baby’s needs as he grows. The breast milk a mother produces for her premature baby differs from the milk she would produce for a full-term newborn, and that differs from the milk she’ll have for her 6-month-old baby. All breast milk, however, contains exactly the nutritional and protective components needed most by each baby at every age.

Colostrum is the first pale yellow milk your breasts produce after giving birth. (You may have noticed beads of colostrum on your nipples in the last weeks of pregnancy.) It’s so high in antibodies that some people call it a baby’s first immunization. It’s higher in protein, minerals, salt, vitamin A, nitrogen, white blood cells, and certain antibodies, and has less fat and sugar than mature milk. Colostrum also has a slightly laxative effect and helps a newborn rinse his gastrointestinal tract of meconium, the waste product accumulated before birth, thereby reducing the risk of jaundice. A little colostrum goes a long way. You may not feel as if you’re producing much, but each drop is packed with nutritional and protective components.

Mature milk comes in approximately two to four days after your baby’s born, depending on the frequency of nursing in the first hours and days after birth. and is produced in greater amounts than colostrum. (Moms often produce too much at first, until their baby’s appetite and nursing frequency match the amount produced to the amount needed.) Mature milk contains water, fat, carbohydrates, protein, vitamins and minerals, amino acids, enzymes, and white cells. Over the course of a feeding, breast milk changes from foremilk, high in water and lactose, to hindmilk, high in fat and calories. After the first few weeks of nursing, your breast milk will contain fewer white cells and more of another antibacterial enzyme, lysozyme, the level of which stays high as long as breastfeeding continues. The quantity of milk you produce increases along with your baby’s weight and appetite until solid food becomes a daily part of his diet.

Breast milk contains more than 200 known beneficial elements, with more being discovered all the time. For example, researchers believe that a recently discovered fatty acid in breast milk promotes the growth of a baby’s brain and retina and may even enhance cognitive development. Many of these elements, including infection-fighting white cells, can’t be manufactured.