Chemistry and Biological Properties of Human Milk

Human milk contains several solid components, water, and wide range of bioactive compounds. Over the evolutionary course of human development, a number of adaptations have resulted in the production of nonnutritive actions associated with breast feeding. In that regard, bioactive compounds in human milk appear not only to compensate for developmental delays in the infants' gastrointestinal tract but also encourage the symbiotic colonization of enteric bacteria that inhibit the growth of bacterial and viral pathogens. Research has also linked these bioactive compounds to certain aspects of the growth and proper development of brain and peripheral nervous system during early infancy. In this review we have summarized what has been learned about the spectrum of nutritive and biological agents in human milk, their physical distribution in human milk over the course of lactation, whether the physical structures and functions of these ingested agents are modified by digestive processes; the precise chemical and cellular loci of their actions, and their short- and long-term biochemical consequences. Although much is still unknown about human milk, and how to optimize infant nutrition substitutes, new information is constantly being discovered. Human milk is and will remain the one standard for infant nutrition by which all infant foods should be compared. It is our species-specific food.