Microbiome Resource Center

Microbiome Resource Center

May 31, 2017
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Breast milk contributes nearly 30% of bacteria to infant gut microbiome

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Bacteria within breast milk, as well as on a mother’s areolar skin, contributed significantly to infant gut bacterial communities, the benefits of which continued after infants began eating solid foods, according to research published in JAMA Pediatrics.

“Studies show that breastfeeding confers protection against respiratory and gastrointestinal tract infections and allergic diseases in addition to reducing the risk of chronic diseases, such as diabetes, obesity and inflammatory bowel disease,” Grace M. Aldrovandi, MD, division chief and professor of pediatrics at the University of California, Los Angeles, and colleagues wrote. “Most microbiota research on the breastfeeding effects to date has focused on infant stool. Little is known about the vertical transfer of breast milk microbes from mother to infant.”

Grace Aldrovandi
Grace M. Aldrovandi

To establish a connection between maternal breast milk, areolar skin and an infant’s gut bacterial communities, the researchers measured the composition of bacteria in these maternal factors and in infant stool samples through 16S ribosomal RNA-gene sequencing. The prospective, longitudinal study included 107 pairs of healthy mothers and infants in Los Angeles and St. Petersburg, Fla. between Jan. 1, 2010, and Feb. 28, 2015.

For the 107 pairs (median age of specimen collection=40 days), 43% included male infants. All three sample types included different forms of bacterial communities, with noted distinctions made in composition and diversity. Bacteria in a mother’s breast milk and areolar skin were also more strongly related to their own child’s gut microbial communities than those of another  mother.

Infants who received 75% or more of their daily milk intake through breastfeeding within the first 30 days of life obtained an average of 27.7% of bacteria from breast milk and 10.3% from areolar skin. The amount of daily breast milk consumed in a dose-dependent manner was related to bacterial diversity and composition changes. This held true even after solid foods were introduced into an infant’s diet.

“Our data do not exclude the possibility that bacteria from infants’ stool seed the mother’s microbiome,” Aldrovandi and colleagues wrote. “It is likely that bacteria cycle between the mother and infant are in a constant exchange. However, we favor the idea that transfer of bacteria primarily occurs from mother to infant.” — by Katherine Bortz

Disclosure: The researchers report no relevant financial disclosures.