That also breaks down the proteins in the milk. I highly recommend kellymom as q site with lost of breastfeeding stuff. I'm not sure if this app will let me post the link.
Do not put your breast milk in the microwave. It can overheat and burn your baby and it destroys the proteins in the milk as well. I always run mine under warm water or have it sitting in a bowl of warm water. Also don't shake breast milk, stir it.