Role of human milk components in gastrointestinal development: Current knowledge and future needs

Human milk (HM) is a complex physiological fluid with multifunctional roles within the gastrointestinal tract that facilitate the successful postnatal adaptation of the newborn by stimulating cellular growth and digestive maturation, the establishment of symbiotic microflora, and the development of gut-associated lymphoid tissues. An intricate mixture of bioactive proteins, lipids. and carbohydrates that is unique to milk supports these processes and provides important signals to the developing intestine. The complexity of HM composition and the potential interactions among milk components has hampered our understanding of how HM components affect gastrointestinal development. Furthermore, limited information exists about the fundamental mechanisms of postnatal intestinal growth of healthy infants, further hindering our ability to delineate the role of HM in regulating this process. In this paper, evidence for the role of HM components in early intestinal development is summarized, with a discussion of the limitations of existing data, and suggestions are made for future research that is needed to delineate the biology of HM, the physiology of postnatal intestinal development, and the complexity of potential interactions that occur between HM components and the developing neonate.