Human breastmilk is the primary source of nutrition for newborn babies. It contains many microbes that play a major role in the development of a child’s immune system and that help protect against infection and inflammation. It is well known that breastmilk is rich in the microbial community that helps to shape the development of the gut microbiome of breastfed babies.

In a recent Danish study published in Nature Microbiology, researchers investigated the association between breastmilk and Bifidobacteria in improving infants’ health. Fifty-nine healthy infants (30 male & 29 female) were included in the study. The study included single birth and full-term infants aged 9 months ± 2 weeks at the start. Infants with chronic illness were not included in the study. Data about medication, prevalence of breast and formula feeding, exclusive breastfeeding duration and the time of introducing solid foods were also recorded by parental questionnaires.

Results from the study showed that, a significant high level of aromatic lactic acids was observed in the stool samples obtained from the breastfed infants. The fecal concentration of aromatic lactic acids was found to be positively associated with the abundance of human milk oligosaccharide-degrading Bifidobacterium species, including Bifidobacterium longum, B. breve and B. bifidum. These Bifidobacterium species found to have the ability to convert aromatic amino acids (tryptophan, phenylalanine and tyrosine) into aromatic lactic acids (indolelactic acid, phenyllactic acid and 4-hydroxyphenyllactic acid) via aromatic lactate dehydrogenase (ALDH). These Bifidobacterium-derived aromatic lactic acids were found to be associated with the capacity to activate the aryl hydrocarbon receptor (AhR), a receptor important for controlling intestinal homoeostasis and immune responses.

Therefore, this study suggests that microbial metabolites produced by breastmilk-promoted Bifidobacterium species may impact the immune function in early life.