A massive body of scientific literature, most of which has been generated since the 1970s, reports the biochemistry of human milk (Goldman & Goldblum 1995; Hanson 1998; Wold & Hanson 1994; Xanthou, Bines & Walker 1995). Human milk changes composition from colostrum, to transitional, to mature milk. It changes from morning to night and from the beginning to the end of breastfeeds. Concentrations of protein, fat, carbohydrates, minerals and cells change and physical properties such as osmolarity and pH vary (Lawrence 1999). The bioactivity of more than 200 constituents has been discovered in human milk and for many of these the immunologic significance is yet to be explored.