Mary Francell, Atlanta, Georgia, USA

In recent years, there has been widespread interest in the role of beneficial bacteria in the human intestinal tract and throughout the body. Commensal  microbes (the normal microflora on our body surfaces) are believed to be involved in everything from regulating immune function to secreting neurotransmitters. Babies get these microbes primarily from their mothers—and breastfeeding plays a major role in their colonization.

Breast milk influences the microflora

Infant gut populations are subject to many variations based on life history, genetics, antibiotic use, ancestral diets, type of birth and more. Some research has even suggested that obesity or stress in a mother, or even the baby’s gender, can influence the microbial composition of human milk. Geographic location is quite significant as well; for example, subsistence communities (those relying on natural resources) tend to have a wider variety of gut bacteria compared to  Western, Educated, Industrialized, Rich and Democratic (WEIRD) societies. However the most important influence on the type of microorganisms on our skin or in our bodies appears to be whether or not a baby receives anything other than breast milk.

An infant’s microbiome (the microorganisms in his body) is formed from several sources: skin-to-skin contact, passage through the birth canal, and bacteria acquired in utero. But a significant portion comes from mothers’ milk, when maternal gut bacteria migrate to the mammary glands and are ingested by the baby. These milk-oriented microbes (MOMs), particularly Bifidobacterium longum infantis (B. infantis), are nourished by another remarkable component of breast milk: human milk oligosaccharides (HMOs).

Human milk oligosaccharides (HMOs)

There are approximately 400 to 1000 different types of HMOs and each mother produces her own individual fingerprint of approximately 50 of these types. Even though HMOs comprise the third largest component of human milk, babies cannot digest these complex sugar molecules. HMOs pass through to the digestive tract, where they not only feed MOMs, but also help bind and inactivate pathogenic bacteria (bacteria that cause infection). This binding capacity is thought to be one reason that the human immunodeficiency virus (HIV) is not easily transmitted through  mother’s milk. In addition, B. infantis digests HMOs far more completely than do other beneficial organisms, and in the process releases both short chain fatty acids that feed the infant’s intestinal lining and sialic acid, which promotes rapid brain growth.

Better health and development

At the 2016 conference of the International Lactation Consultant Association, anthropologist Katie Hinde , PhD discussed how a preponderance of “breastfed-type” bifidos bacteria in a baby’s gut, especially B. infantis, is associated with better health outcomes and development, including improved immune function and decreased incidence of necrotizing enterocolitis ( a serious intestinal disease) in preterm infants. Another of the  fascinating ways microbes may be involved in enhanced immunity is through the interaction of human milk and infant (but not adult) saliva. This combination produces a form of hydrogen peroxide that destroys pathogenic bacteria, while at the same time providing nucleosides and nucleobases (building blocks of genetic material) to nourish beneficial organisms. Dr. Hinde and other researchers have even theorized that some MOMs may secrete specific neurotransmitters (chemical messengers) to help regulate behavior in infants, possibly leading to better growth through conservation of energy.

We can now add both probiotic and prebiotic benefits to the long list of breast milk’s amazing attributes.  For more fascinating information on breast milk composition and function, check out Dr. Hinde’s blog “Mammals Suck… Milk!” at

Al-Shehri, Saad S. et al. “Breastmilk-Saliva Interactions Boost Innate Immunity by Regulating the Oral Microbiome in Early Infancy.” Ed. Luis Eduardo Soares Netto. PLoS ONE 10.9 (2015): e0135047. PMC. Web. 1 Nov. 2016.
Ardythe L. Morrow, Guillermo M. Ruiz-Palacios, Xi Jiang, and David S. Newburg
Human-Milk Glycans That Inhibit Pathogen Binding Protect Breast-feeding Infants against Infectious DiarrheaJ. Nutr. 2005 135: 5 1304-1307
Armanian, Amir-Mohammad et al. “The Effect of Neutral Oligosaccharides on Fecal Microbiota in Premature Infants Fed Exclusively with Breast Milk: A Randomized Clinical Trial.” Journal of Research in Pharmacy Practice 5.1 (2016): 27–34. PMC. Web. 2 Nov. 2016.
Bentley, Jason P. et al. “Gestational Age, Mode of Birth and Breastmilk Feeding All Influence Acute Early Childhood Gastroenteritis: A Record-Linkage Cohort Study.” BMC Pediatrics 16 (2016): 55. PMC. Web. 1 Nov. 2016.
Bode, Lars et al. “Human Milk Oligosaccharide Concentration and Risk of Postnatal Transmission of HIV through Breastfeeding.” The American Journal of Clinical Nutrition 96.4 (2012): 831–839. PMC. Web. 3 Nov. 2016.
Cary R. Allen-Blevins, David A. Sela, and Katie Hinde Milk bioactives may manipulate microbes to mediate parent–offspring conflictEMPH (2015) 2015: 106-121 doi:10.1093/emph/eov007 first published online April 2, 2015
Cong, Xiaomei et al. “Gut Microbiome Developmental Patterns in Early Life of Preterm Infants: Impacts of Feeding and Gender.” Ed. Francesco Cappello.PLoS ONE 11.4 (2016): e0152751. PMC. Web. 3 Nov. 2016.
Kumar Himanshu, du Toit Elloise, Kulkarni Amruta, Aakko Juhani, Linderborg Kaisa M., Zhang Yumei, Nicol Mark P., Isolauri Erika, Yang Baoru, Collado Maria C., Salminen Seppo. “Distinct Patterns in Human Milk Microbiota and Fatty Acid Profiles Across Specific Geographic Locations.” Frontiers in Microbiology, vol. 7, 2016.
Mueller, Noel T. et al. “The Infant Microbiome Development: Mom Matters.”Trends in molecular medicine 21.2 (2015): 109–117. PMC. Web. 3 Nov. 2016.
Obregon-Tito, Alexandra J. et al. “Subsistence Strategies in Traditional Societies Distinguish Gut Microbiomes.” Nature Communications 6 (2015): 6505. PMC. Web. 3 Nov. 2016.
Pacheco, Alline R. et al. “The Impact of the Milk Glycobiome on the Neonate Gut Microbiota.” Annual review of animal biosciences 3 (2015): 419–445. PMC. Web. 3 Nov. 2016.
Romano-Keeler, Joann, and Jörn-Hendrik Weitkamp. “Maternal Influences on Fetal Microbial Colonization and Immune Development.” Pediatric research77.0 (2015): 189–195. PMC. Web. 2 Nov. 2016.
Smilowitz, Jennifer T. et al. “Breast Milk Oligosaccharides: Structure-Function Relationships in the Neonate.” Annual review of nutrition 34 (2014): 143–169.PMC. Web. 2 Nov. 2016.
Underwood, Mark A. et al. “Bifidobacterium Longum Subspecies infantis: Champion Colonizer of the Infant Gut.” Pediatric research 77.0 (2015): 229–235. PMC. Web. 3 Nov. 2016.
Yong, Ed. Breast-feeding the Microbiome. The New Yorker. July 22, 2016.


Mary Francell and her husband Howard are the parents of three breastfed children, aged 25, 21 and 18. She has been an LLL Leader for over 20 years and is currently Area Professional Liaison for LLL of Georgia, USA and a Contributing Editor for Leader Today. An International Board Certified Lactation Consultant, Mary works part-time at a pediatric office and also sees clients on contract with a private lactation practice in Atlanta, Georgia, USA.
Print Friendly