Breastmilk, the Microbiome, and the Enduring Health Corollary

Christian Maino Vieytes, B.S. Nutritional Sciences, University of Maryland, College Park, M.S. Candidate, Division of Nutritional Sciences, University of Illinois at Urbana-Champaign

Knowledge about the benefits of breastfeeding has exploded in the last 20 years thanks, in part, to the burgeoning realm of microbiome science, or the study of the gut flora. These terms collectively refer to all of the micro-organisms, and their genetic material, that inhabit our gastrointestinal tract (primarily from the stomach and downwards into the colon and rectum). We now understand a great deal about how components in breast milk prepare an infant’s microbiome and other biological systems for the challenges that it faces as it develops into a growing young adult. Remarkably, these effects are now understood to extend into adulthood and later life.

Mammals—a term that encompasses us, humans, and other lactating animal species—are recognized for their unique ability to produce breast milk and enter a cycle of lactation, following the cycles of pregnancy and parturition. What is the role of breast milk? Primarily, breast milk provides an adequate amount of calories and the scope of nutrients necessary for meeting the infant’s growth trajectory. Chemical constituent factors residing in breast milk are essential for promoting rapid and sound neonatal growth. These factors include hormones (growth factors, estrogens, thyroid gland hormones, among a variety of others) in addition to macronutrients (carbohydrates, proteins, and fats) and micronutrients (vitamin and minerals).¹ Human milk is also host to a list of immune factors (antibodies and other proteins that stimulate the infant’s immune system) that help safeguard the developing infant’s organs and tissues against life-threatening infectious illnesses^2,3. Remarkably, prolonged consumption of breastmilk during infancy has been demonstrated to protect the child against the development of asthma, celiac disease, type 1 and type 2 diabetes, allergies, and obesity later in life. ^4,5 

Intestinal Development

A more recent revelation is the role that specific carbohydrates (termed complex oligosaccharides in the world of breast milk research) in human milk provide for developing the gastrointestinal microbiome of the infant. Astoundingly, breast milk consumption has been associated with a more diverse microbiome, a marker of health.⁴ This comes from the consumption of the breastmilk itself as well from the exchange of microbes from the surface of the mother’s skin during the act of breastfeeding.^4,6,7 Multiple studies have consistently demonstrated that exclusively breastfed infants differ from and have more healthful microbiome profiles compared to their non-exclusively breastfed counterparts.⁸ Unique proteins in the milk are understood to promote the development of lymphoid tissue, which is the layer of immune tissue that resides below the superficial membranes of the gastrointestinal tract that sift through foreign materials and micro-organisms that constantly challenge the host.³ In essence, we see the profound effects that human milk components have on intestinal development and how appropriate development of the gut is integral to overall health. Additionally, health benefits imparted to the mother may include: a reduction in post-partum depression risk as well as a reduction in risks of breast and ovarian cancer.^9,10

Current Recommendations

The American Academy of Pediatrics currently recommends that mothers exclusively breastfeed their children for at least 6 months and continue to do so, as soft and solid foods are introduced, for 1 year or longer.¹¹ Interestingly, population-level studies have demonstrated that only 13% of the population currently meets the 6-month recommendation.¹¹ Many of the aforementioned benefits are contingent on the cumulative duration of the exclusive breastfeeding period. That is, many of these benefits are associated with extended cumulative periods of exclusive breastfeeding.¹¹

Special Considerations

The benefits of breastfeeding need to be balanced in consideration of the challenges and barriers that mothers face for breastfeeding their infants. Obstacles to lactation need to be considered, and we must be sensitive to them. Establishing and maintaining a breast milk supply is one of the frequently cited challenges mothers encounter.¹² Moreover, mothers with certain conditions or who take certain medications may be discouraged from breastfeeding their infants.¹³ Working closely with one’s pediatrician and lactation consultant on appropriate lactation practices and management is instrumental for ensuring good breastfeeding outcomes.¹⁴

References

1. Grosvenor CE. Hormones and growth factors in milk. Endocr Rev. 1993;14(6):710-728. doi:10.1210/er.14.6.710
2. Lönnerdal B. Human Milk Proteins. In: Pickering LK, Morrow AL, Ruiz-Palacios GM, Schanler RJ, eds. Protecting Infants through Human Milk. Vol 554. Boston, MA: Springer US; 2004:11-25. doi:10.1007/978-1-4757-4242-8_4
3. Donovan SM. Role of human milk components in gastrointestinal development: Current knowledge and future NEEDS. J Pediatr. 2006;149(5):S49-S61. doi:10.1016/j.jpeds.2006.06.052
4. Mueller E, Blaser M. Breast milk, formula, the microbiome and overweight. Nat Rev Endocrinol. 2018;14(9):510-511. doi:10.1038/s41574-018-0066-5
5. Greer FR, Sicherer SH, Burks AW, and the Committee on Nutrition and Section on Allergy and Immunology. Effects of Early Nutritional Interventions on the Development of Atopic Disease in Infants and Children: The Role of Maternal Dietary Restriction, Breastfeeding, Timing of Introduction of Complementary Foods, and Hydrolyzed Formulas. PEDIATRICS. 2008;121(1):183-191. doi:10.1542/peds.2007-3022
6. Pannaraj PS, Li F, Cerini C, et al. Association Between Breast Milk Bacterial Communities and Establishment and Development of the Infant Gut Microbiome. JAMA Pediatr. 2017;171(7):647. doi:10.1001/jamapediatrics.2017.0378
7. Valdes AM, Walter J, Segal E, Spector TD. Role of the gut microbiota in nutrition and health. BMJ. June 2018:k2179. doi:10.1136/bmj.k2179
8. Ho NT, Li F, Lee-Sarwar KA, et al. Meta-analysis of effects of exclusive breastfeeding on infant gut microbiota across populations. Nat Commun. 2018;9(1):4169. doi:10.1038/s41467-018-06473-x
9. Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50 302 women with breast cancer and 96 973 women without the disease. The Lancet. 2002;360(9328):187-195. doi:10.1016/S0140-6736(02)09454-0
10. Lipworth L. History of Breast-Feeding in Relation to Breast Cancer Risk: a Review of the Epidemiologic Literature. J Natl Cancer Inst. 2000;92(4):302-312. doi:10.1093/jnci/92.4.302
11. SECTION ON BREASTFEEDING. Breastfeeding and the Use of Human Milk. PEDIATRICS. 2012;129(3):e827-e841. doi:10.1542/peds.2011-3552
12. Callen J, Pinelli J. A REVIEW OF THE LITERATURE EXAMINING THE BENEFITS AND CHALLENGES, INCIDENCE AND DURATION, AND BARRIERS TO BREASTFEEDING IN PRETERM INFANTS: Adv Neonatal Care. 2005;5(2):72-88. doi:10.1016/j.adnc.2004.12.003
13. Lawrence RM, Lawrence RA. Given the Benefits of Breastfeeding, what Contraindications Exist? Pediatr Clin North Am. 2001;48(1):235-251. doi:10.1016/S0031-3955(05)70297-2
14. Dobson B, Murtaugh MA. Position of the American Dietetic Association. J Am Diet Assoc. 2001;101(10):1213-1220. doi:10.1016/S0002-8223(01)00298-X

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