Breast milk is an amazingly rich concoction of sugars, fats, and immune factors. It is a carrier for the main payload—a starter microbiota that includes bacteria and fungus from the mother and her mother before her. They are specially plucked from the mother's gut by dendritic cells and then ferried to the milk ducts via the lymphatic system. These microbes are accompanied by a rich broth of prebiotics to feed them. Most of the sugars in milk are for those microbes, not the baby. That seems sadistic, but it's not: The microbes convert those indigestible sugars into energy-packed fatty acids that feed the baby and nourish the gut lining.

Hal and Ava offer an overview of this amazing maternal inheritance.

References

Neu, Josef, and Jona Rushing. “Cesarean versus Vaginal Delivery: Long Term Infant Outcomes and the Hygiene Hypothesis.” Clinics in Perinatology 38, no. 2 (June 2011): 321–31. doi:10.1016/j.clp.2011.03.008.

Boix-Amorós, Alba, Fernando Puente-Sánchez, Elloise du Toit, Kaisa M. Linderborg, Yumei Zhang, Baoru Yang, Seppo Salminen, et al. “Mycobiome Profiles in Breast Milk from Healthy Women Depend on Mode of Delivery, Geographic Location and Interaction with Bacteria.” Appl. Environ. Microbiol., March 1, 2019, AEM.02994-18. https://doi.org/10.1128/AEM.02994-18.

Funkhouser, Lisa J., and Seth R. Bordenstein. “Mom Knows Best: The Universality of Maternal Microbial Transmission.” PLOS Biol 11, no. 8 (August 20, 2013): e1001631. doi:10.1371/journal.pbio.1001631.

Dinan, Timothy G., and John F. Cryan. “Gut Instincts: Microbiota as a Key Regulator of Brain Development, Ageing and Neurodegeneration.” The Journal of Physiology 595, no. 2 (2017): 489–503. https://doi.org/10.1113/JP273106.

Sudo, Nobuyuki, Yoichi Chida, Yuji Aiba, Junko Sonoda, Naomi Oyama, Xiao-Nian Yu, Chiharu Kubo, and Yasuhiro Koga. “Postnatal Microbial Colonization Programs the Hypothalamic-Pituitary-Adrenal System for Stress Response in Mice.” The Journal of Physiology 558, no. Pt 1 (July 1, 2004): 263–75.

Stilling, Roman M., Feargal J. Ryan, Alan E. Hoban, Fergus Shanahan, Gerard Clarke, Marcus J. Claesson, Timothy G. Dinan, and John F. Cryan. “Microbes & Neurodevelopment--Absence of Microbiota during Early Life Increases Activity-Related Transcriptional Pathways in the Amygdala.” Brain, Behavior, and Immunity 50 (November 2015): 209–20. doi:10.1016/j.bbi.2015.07.009.

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