The most common reason mothers probably choose to breastfeed is the knowledge that human milk is the superior infant food. It contains live cells, like those in blood. Some components of human milk also enhance the effects of others, so the ingredients of human milk work together.  Here is Why Human Milk is so Special.In contrast, only a small percentage of some ingredients of formula are absorbed; mixing ingredients in formula does not guarantee they will act together the way they do in human milk.