Breastfeeding is not "best". It's NORMAL. "There is no substance that can come close to human milk. Infant formula, a synthetic human milk substitute, is not a healthy alternative to mother's milk. Formula is missing over 400 ingredients present in human milk, which cannot be duplicated by scientists in a laboratory."
http://hcp.obgyn.net/pregnancy-and-birth/content/article/1760982/1982833