The milk your breast produces after a few days is specifically designed for a newborn human. The fat content, protein type and level, and the balance of vitamins and minerals is exactly geared for your baby. This milk is therefore easier for baby to digest, and baby is able to absorb nutrients from breast milk more completely. This is why breastfeeding protects against iron deficiency for example, for at least six months in spite of the iron levels in breast milk being 20 times less than the level found in formula. The iron in breast milk is more easily available to the baby and is almost all absorbed, whereas very little of the iron in enriched formulas is able to be absorbed by baby.
Breast milk changes throughout a feeding.
The first milk baby receives, called foremilk, is thin and watery, and satisfies thirst. This hindmilk satisfies hunger, and the more of this baby receives, the longer baby will be content. Protection from infection continues with breast milk, although not at such a concentrated level as is found in colostrum. An added bonus is that when baby does become ill, the infecting organism passes into mother through the breast, allowing her to produce antibodies and pass them back to baby in her milk. Baby thus has twice the army of antibodies available to help clear the infection more quickly.