A new study showed that the growth of some microbes was inhibited for up to 24 hours following breastmilk and saliva mixing.

The team's earlier studies had found significant differences in the prevalence of key bacteria within the mouths of breastfed and formula-fed babies and that breastmilk and saliva interactions boost innate immunity by acting in synergy to regulate the oral microbiome of newborn babies.

"Our findings suggest that breastmilk is more than a simple source of nutrition for babies because it plays an important role in shaping a healthy oral microbiome," the senior author said.

"Our previous research found that the interaction of neonatal saliva and breast milk releases antibacterial compounds, including hydrogen peroxide.

"Breastmilk is high in an enzyme called xanthine oxidase which acts on two substrates, found in babies' saliva.

"The release of hydrogen peroxide from this interaction also activates the 'lactoperoxidase system' which produces additional compounds that also have antibacterial activity, and these compounds are capable of regulating the growth of microorganisms.

"In this study, we exposed a variety of microorganisms to breastmilk and saliva mixtures, and found that the growth of these microorganisms was inhibited, immediately and for up to 24 hours, irrespective of whether the microorganism was considered to be 'pathogenic' (harmful) or 'commensal' (normally found) in an infant's mouth."

Authors demonstrate that microbial growth was inhibited predominately, immediately and for up to 24 hr following breastmilk and saliva mixing; however, some microorganisms were able to recover and continue to grow following exposure to these micromolar amounts of hydrogen peroxide. Interestingly, growth inhibition was independent of whether the organisms possessed a catalase enzyme. This study further confirms that this is one mechanism that contributes to the significant differences in the neonatal oral microbiota of breast-fed and formula-fed babies.

The senior author said the composition of newborns' mouth microbiota was an important factor in health and wellbeing. "Changes to these bacterial communities in newborns have important implications for infection or disease early in life," the author said.

"While adult oral microbiota are stable, our studies have shown that the microbiota in the mouths of newborns is much more dynamic and seems to be altered by the mode of feeding within the first few months of life," the author said.

"The combination of breastmilk and saliva has been shown to play an important role in shaping the healthy oral microbiota during the first few months of life, but this also has significant implications for premature or sick babies who are fed via a tube.

"In these cases, the mixing of breastmilk and babies' saliva does not occur and so they do not receive the benefits of the antibacterial compounds released during breastfeeding.

."Other researchers have shown that hydrogen peroxide can remain active at pH levels similar to that of a baby's stomach, so we think that this antimicrobial activity seen in the mouth may also continue within the baby's stomach and intestines.

https://www.qut.edu.au/news?id=137830

https://www.nature.com/articles/s41598-018-33519-3

http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Fthe-efect-of-breastmilk&filter=22