Breast and gut: the relationship between lactating mammary function and neonatal gastrointestinal function

Abstract

HYPOTHESIS Throughout the class mammalia there is an intimate relationship between lactating mammary function and neonatal gastrointestinal function. The extent of the contribution of breast milk to the adaptation of the newborn to extrauterine life is related inversely to the time after conception at which birth occurs in the course of gastrointestinal development. Milk is nutrients packaged for transfer from mother to young, but also contains a range of non-nutrient factors which assist perinatal adaptation. The neonatal gut is adapted not only for the utilization of nutrients provided by milk, but also depends on non-nutrient factors to compensate for its immature digestive and barrier functions, and trophic and other factors to regulate the transition from intrauterine to extrauterine life. During mammalian evolution there has been a trend towards birth later in the course of gastrointestinal development with a consequent reduction in the range of biological functions of milk feeding. This is reflected in the structure and function of the neonatal gut.