<P> The principal proteins are alpha - lactalbumin, lactoferrin (apo - lactoferrin), IgA, lysozyme, and serum albumin . In an acidic environment such as the stomach, alpha - lactalbumin unfolds into a different form and binds oleic acid to form a complex called HAMLET that kills tumor cells . This is thought to contribute to the protection of breastfed babies against cancer . </P> <P> Non-protein nitrogen - containing compounds, making up 25% of the milk's nitrogen, include urea, uric acid, creatine, creatinine, amino acids, and nucleotides . Breast milk has circadian variations; some of the nucleotides are more commonly produced during the night, others during the day . </P> <P> Mother's milk has been shown to supply endocannabinoids (the natural neurotransmitters that cannabis simulates) 2 - Arachidonoyl glycerol, anandamide, oleoylethanolamide, palmitoylethanolamide, N - arachidonoyl glycine, eicosapentaenoyl ethanolamide, docosahexaenoyl ethanolamide, N - palmitoleoyl - ethanolamine, dihomo - γ - linolenoylethanolamine, N - stearoylethanolamine, prostaglandin F2alpha ethanolamides and prostaglandin F2 ethanolamides . They may act as an appetite stimulant, but they also regulate appetite so infants don't eat too much . That may be why formula - fed babies have a higher caloric intake than breastfed babies . </P> <P> Breast milk isn't sterile, but contains as many as 600 different species of various bacteria, including beneficial Bifidobacterium breve, B. adolescentis, B. longum, B. bifidum, and B. dentium . </P>

The primary component of breast milk by volume is