Q&A: Will My Milk Change?
Yes. The milk in the early months is higher in whey protein, which is easier to digest. As the baby gets older, the amount of casein protein, which requires a more mature digestive system to process, increases. Also, every time a mother is exposed to an illness (even before she comes down with symptoms), the antibodies to that illness pass into her milk, so baby's immune system will benefit more as time goes on.