By Stephen Beech

Human breast milk regulates a baby’s mix of microbes – or microbiome – during the child’s first year of life, say scientists.

That in turn lowers the child’s risk of developing asthma, suggests the new study published in the journal Cell.

The findings show that breastfeeding beyond three months supports the gradual maturation of the microbiome in the baby’s digestive system and nasal cavity, the upper part of the respiratory tract.

But stopping breastfeeding earlier than three months disrupts the paced development of the microbiome and was linked to a higher risk of pre-school asthma, according to the American and Canadian research team.

They say certain components in breast milk – such as complex sugars called human milk oligosaccharides – can only be broken down with the help of certain microbes.

That provides a “competitive advantage” to microbes capable of digesting those sugars.

By contrast, babies who are weaned earlier than three months from breast milk and who then rely solely on formula feeding, become home to a different set of microbes — ones that will help the child to digest the components in the formula.

While many of the microbes that thrive on formula do eventually end up in all babies, the research team showed that their early arrival is linked to an increased risk of asthma.

Study co-senior investigator and computational biologist Dr. Liat Shenhav said: “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.

“Healthy microbiome development is not only about having the right microbes.

“They also need to arrive in the right order at the right time.”

Dr. Shenhav, of New York University’s Grossman School of Medicine, worked alongside study co-senior investigator Professor Meghan Azad, of the University of Manitoba in Canada.

They also discovered that the bacterial species called Ruminococcus gnavus appeared much sooner in the guts of children who were weaned early from breast milk than in those of youngsters who were exclusively breastfed.

The research team explained that the bacterium is known to be involved in the production of molecules called short-chain fatty acids, and the formation and breakdown of the amino acid tryptophan.

Both tryptophan and its metabolites have been linked to immune system regulation and disruption in previous research, including an increased risk of asthma.

The research team noted that beyond aiding in digestion, an infant’s microbiome plays a “crucial” role in the immune system’s development.

They tracked the ebb and flow of microbes in the guts and noses of babies during their first year of life, as well as details on breastfeeding and the composition of their mothers’ milk.

All the children and their mums were participating in a long-term research project that has been studying the same 3,500 Canadian children at different stages of life from the womb well into adolescence.

The data provided enabled the team to “detangle” the impact of breastfeeding on a baby’s microbiome from several other environmental factors, including prenatal smoke exposure and antibiotics.

Even when those factors were accounted for, they found that breastfeeding duration remained a “powerful” determinant for the child’s microbial makeup over time.

The researchers also used the microbial dynamics and data on milk components to train a machine-learning model that accurately predicted asthma years in advance.

The team then created a statistical model to learn causal relationships, which showed that the primary way breastfeeding reduces asthma risk is through shaping the baby’s microbiome.

Dr. Shenhav said: “The algorithms we developed provide valuable insights into microbial dynamics during an infant’s first year of life and how these microbes interacted with the infant.

“These insights allowed us to move beyond identifying associations, enhancing our ability to make predictions and explore causal relationships.”

She added: “Our research highlights the profound impact of breastfeeding on the infant microbiome and breastfeeding’s essential role in supporting respiratory health.

“By uncovering the mechanisms behind the protective effects of breast milk, as demonstrated in this study, we aim to inform national guidelines on breastfeeding and weaning from breast milk in a data-driven manner.

“With further research, our findings could also contribute to developing strategies to prevent asthma in children who cannot be breastfed for at least three months.”

Source: https://www.purdueexponent.org/