Breastfeeding helps develop a healthy gut and reduce the risk of asthma in babies less than a year old, according to a study published today.
U.S. and Canadian scientists found that breastfeeding beyond three months affected the gut, immune system and asthma risk of babies by building a healthy gut microbiome—meaning a community of microorganisms.
"Just as a pacemaker regulates the rhythm of the heart, breastfeeding and human milk set the pace and sequence for microbial colonization in the infant's gut and nasal cavity, ensuring that this process occurs in an orderly and timely manner," said computational biologist Liat Shenhav, one of the senior study authors, in a statement.
"Our research highlights the profound impact of breastfeeding on the infant microbiome and breastfeeding's essential role in supporting respiratory health," she said.
The children and mothers were all participants in the CHILD Cohort Study: a long-term research project studying 3,500 Canadian children from the womb into adolescence.
In recent years, research has revealed the myriad ways that a healthy gut microbiome impacts overall health and is especially crucial for good digestion, metabolism, immunity and mental health.
Scientists in this study found that, even when they had accounted for other environmental factors—such as smoke exposure, antibiotics and the mother's history of asthma—the duration in which a baby was breastfed remained a powerful indicator of that child's microbial makeup over time.
There were several reasons why this might be the case, the researchers found. For example, breast milk contains complex sugars called human milk oligosaccharides that can only be broken down by specific microorganisms.
Formula is made up of different components, so different microbes are needed for digestion—and this gives certain microbes a competitive advantage in the gut, depending on a baby's diet.
Many of the microbes that developed in formula-fed babies would end up in the breastfed babies too, but later down the line—and the scientists found their early arrival was linked to asthma.
"Healthy microbiome development is not only about having the right microbes. They also need to arrive in the right order at the right time," said Shenhav.
Specifically, a bacterial species called Ruminococcus gnavus appeared much sooner in the guts of children who were weaned off breast milk early, compared with breastfed children.
These bacteria are known to be connected to the regulation and disruption of the immune system, and to an increased risk of asthma.
Shenhav said that uncovering these mechanisms could inform national guidelines on breastfeeding and weaning, and hoped that future research would help develop strategies to prevent asthma in children who could not be breastfed for their first three months.
The study measured microbes in the guts and noses of infants during their first year of life, as well as tracking details about breastfeeding and the mothers' breast milk.
The researchers used artificial intelligence, in the form of a machine-learning model, to accurately predict asthma years in advance based on breastfeeding habits. A statistical model helped the scientists identify causal relationships.
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Reference
Shenhav, L., Fehr, K., Reyna, M. E., Petersen, C., Dai, D. L.Y., Dai, R., Breton, V., Rossi, L., Smieja, M., Simons, E., Silverman, M. A., Levy, M., Bode, L., Field, C. J., Marshall, J. S., Moraes, T. J., Mandhane, P. J., Turvey, S. E., Subbarao, P., Surette, M. G., & Azad, M. B. (2024). Microbial colonization programs are structured by breastfeeding and guide healthy respiratory development. Cell, 187. http://dx.doi.org/10.1016/j.cell.2024.07.022
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