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 http://mammalssuck.blogspot.com/?view=magazine.
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