34 Mothers’ own milk provides personalized nutrition and protection to optimize short- and long-term health outcomes in term and preterm infants

Abstract The human infant is the most immature of all mammals at birth, yet boasts the kingdom’s largest and most complex brain, which grows exponentially between 35 weeks of gestation and 2 years of age. Mothers’ own milk (MOM; excludes donor human milk; DHM) has evolved to provide personalized nutrition and bioactive components that prioritize brain growth, development and neuroprotection, as well as maturation of other body organs and metabolic and immunomodulatory pathways. Because of high MOM lactose and lipid to support the brain, MOM protein is the lowest among mammals, programming slow body growth, which is linked to lower obesity risk into adulthood. Clinical studies, albeit mostly observational due to inability to ethically randomize diet, have demonstrated improved long-term outcomes consistent with these components, including lower risks of non-communicable chronic diseases and higher measures of neurocognitive outcome. MOM components vary markedly as a function of lactation phase, with lactoferrin, secretory IgA, leptin, growth factors, gut colonizing components and other bioactives highest in the first postpartum month, suggesting programming and protection roles. Although MOM has not evolved to support optimal growth of preterm infants, necessitating exogenous fortification, the immature mammary gland secretes many bioactive components in higher concentrations and for a longer duration postpartum, with several studies suggesting a critical window for receipt of high-dose MOM during the first month post-birth in preterm infants. DHM is significantly less effective due to maternal donation during later lactation phases, storage, freeze-thaw cycles and pasteurization. Research priorities for feeding preterm infants will be summarized.