New Study Shows How “Good Bacteria” in Breast Milk Changes Over Time

According to the scientists, bacteria in breast milk may change to help offer baby continued protection and immunity.
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profile picture of Nehal Aggarwal
February 25, 2021
Mom sitting and breastfeeding her baby.
Image: Lea Jones

The benefits of breastfeeding have been known for a long time: Breast milk carries protective properties and beneficial bacteria that help baby’s immune system. But most studies done on breast milk have focused on mothers who live in high-income countries. One recent study is aiming to change that in order to learn more about how breast milk’s protective properties work.

The study, conducted by scientists from Montreal and Guatemala and published in Frontiers in Microbiology, looked at how the “good bacteria” in breast milk may change over time and play a role in baby’s development and health. Researchers analyzed breast milk from a small group of women at both early (between 6 and 46 days postpartum) and late (between 109 and 184 days postpartum) stages of breastfeeding.

All the women delivered vaginally and were Mam-Mayan mothers living in rural communities in the Western Highlands of Guatemala. Mam-Mayan mothers largely breastfeed baby exclusively for the entire six months, as recommended by the World Health Organization. (In North America, only 26 percent of moms do so.) The longer feeding time allowed the scientists to observe how the microbiome (which is genetic material consisting of bacteria, fungi, viruses, etc.) in human milk changes over time, Emmanuel Gonzalez, co-author of the study and a bioinformatics specialist at McGill University, explained in a press release.

The researchers used high-resolution imaging technology that was originally developed to find bacteria on the International Space Station for the analysis. They found a range of microbiome species that had never before been identified in human milk. The study also found the microbiome bacteria in breast milk could help protect baby against toxins, offering further insight on how breastfeeding could help build baby’s immunity. Plus, researchers found that common changes occur in the microbiome of healthy human breast milk in the first six months of breastfeeding, suggesting that the changes play a continued and positive role in baby’s health.

“Some bacterial species we observed in our sample breast milk had a common function in destroying foreign substances or xenobiotics and could play a role in protection against toxins and pollutants,” Gonzalez said.

The researches also highlight the importance of looking at microbiomes at different stages in breastfeeding from diverse communities to form a more complete picture of the human milk microbiome and the factors that help shape it.

“Studying microbiomes of diverse communities is important in order to understand the variation present in humans,” co-author Kristine Koski, an Associate Professor in the School of Human Nutrition at McGill, also said in the release. “Most human milk microbiome studies have been conducted with mothers from high income countries, generating an incomplete picture of the important bacteria passed to infants during early development.”

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.

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