Parental factors that impact the ecology of human mammary development, milk secretion, and milk composition—a report from “Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)” Working Group 1 The American Journal of Clinical Nutrition
Abstract The goal of Working Group 1 in the Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN) Project was to outline factors influencing biological processes governing human milk secretion and to evaluate our current knowledge of these processes. Many factors regulate mammary gland development in utero, during puberty, in pregnancy, through secretory activation, and at weaning. These factors include breast anatomy, breast vasculature, diet, and the lactating parent’s hormonal milieu including estrogen, progesterone, placental lactogen, cortisol, prolactin, and growth hormone. We examine the effects of time of day and postpartum interval on milk secretion, along with the role and mechanisms of lactating parent-infant interactions on milk secretion and bonding, with particular attention to the actions of oxytocin on the mammary gland and the pleasure systems in the brain. We then consider the potential effects of clinical conditions including infection, pre-eclampsia, preterm birth, cardiovascular health, inflammatory states, mastitis, and particularly, gestational diabetes and obesity. Although we know a great deal about the transporter systems by which zinc and calcium pass from the blood stream into milk, the interactions and cellular localization of transporters that carry substrates such as glucose, amino acids, copper, and the many other trace metals present in human milk across plasma and intracellular membranes require more research. We pose the question of how cultured mammary alveolar cells and animal models can help answer lingering questions about the mechanisms and regulation of human milk secretion. We raise questions about the role of the lactating parent and the infant microbiome and the immune system during breast development, secretion of immune molecules into milk, and protection of the breast from pathogens. Finally, we consider the effect of medications, recreational and illicit drugs, pesticides, and endocrine-disrupting chemicals on milk secretion and composition, emphasizing that this area needs much more research attention. Keywords: human milk, milk secretion, chronobiology, oxytocin, obesity, diabetes, membrane transporters, model systems, microbiome, environmental toxins
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Margaret C Neville, Ellen W Demerath, Jennifer Hahn-Holbrook et al.. Parental factors that impact the ecology of human mammary development, milk secretion, and milk composition—a report from “Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)” Working Group 1. The American Journal of Clinical Nutrition. (2023). https://doi.org/10.1016/j.ajcnut.2022.11.026 Margaret C Neville, Ellen W Demerath, Jennifer Hahn-Holbrook, Russell C Hovey, Jayne Martin-Carli, Mark A McGuire, Edward R Newton, Kathleen M Rasmussen, Michael C Rudolph, Daniel J Raiten
1Department of Obstetrics and Gynecology, University of Colorado, Aurora, CO, USA 2Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, United States 3Department of Psychological Sciences, University of California Merced, Merced, CA, United States 4Department of Animal Science, University of California Davis, Davis, CA, United States 5Department of Pediatrics, University of Colorado, Aurora, CO, United States 6Idaho Agricultural Experiment Station, University of Idaho, Moscow, ID, United States 7Department of Obstetrics and Gynecology, Brody School of Medicine, East Carolina University, Greenville, NC, United States 8Nancy Schlegel Meinig Professor of Maternal and Child Nutrition, Division of Nutritional Sciences, Cornell University, Ithaca, NY, United States 9The University of Oklahoma Health Science Center, Oklahoma City, OK, United States 10Pediatric Growth and Nutrition Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States 