In a recently published paper in the journal of the American Gastroenterological Association SyMBIOTA researchers have found a causal link between caesarean section birth, low intestinal microbiota and peanut sensitivity in infants, and they report the effect is more pronounced in children of Asian descent than others.

The research team analyzed the gut bacteria of 1,422 infants in the CHILD Cohort Study, by examining fecal samples collected at three or four months of age and again at one year. They identified four typical trajectories for bacterial development, including one in which the infants had persistently low levels of Bacteroides, a type of bacteria known to be critical to immune system development. This profile was most common in babies born by caesarean section.

Babies born by caesarean section to mothers of Asian descent are eight times more likely to develop peanut allergy by age three.

Dr Kozyrskyj's main collaborator Hein Tun (pictured below), is a former post-doctoral fellow at U of A who is now assistant professor of public health at the University of Hong Kong.

The full interview of Dr Kozyrskyj and Tun on this research was featured in the University of Alberta Folio website.

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Updated: Apr 25

SyMBIOTA research published in the journal Gastroenterology explores how cesarean delivery and other birth events infuence a baby’s gut microbiome at three and 12 months of age, and how this can increase the risk of allergies and obesity later in childhood.

The research used data from 1,667 mothers and infants participating in the CHILD Cohort Study. The researchers analyzed the gut microbes in infant stool samples, and cross-referenced this analysis with body-mass index (BMI) measurements and the results of allergy tests that these same children underwent at ages one and three years.

The study found that infants born by cesarean section were more likely to have a high BMI score at one and three years of age. The researchers also found that at three months these babies had an altered ratio of two bacteria – Enterobacteriaceae and Bacteroidaceae – and that this change represented the dominant path to overweight. At 12 months of age the same infants had a higher Enterobacteriaceae/Bacteroidaceae (E/B) ratio and colonization with the bacterium Clostridioides difficile (C. difficile), which the researchers identified as the main pathways leading to allergic sensitization.

Infants born after prolonged labour associated with a first pregnancy were also found to be at a higher risk for these health outcomes, with the E/B abundance ratio again being the most important microbiota mediator to overweight and allergic sensitization, and with Bifidobacterium also playing a role in overweight development.

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Updated: Apr 25

The study, published in the journal Gut Microbes, found that infant vitamin D supplementation is associated with compositional changes in a baby’s microbiome – notably a lower abundance of the bacteria Megamonas – at three months of age.

The researchers examined fecal samples taken during home visits from 1,157 infants who are part of the CHILD Cohort Study – a national study that is following nearly 3,500 Canadian children from before birth to adolescence with the primary goal of discovering the root causes of allergies, asthma, obesity and other chronic diseases.

They found that direct vitamin D supplementation of infants with vitamin D drops was associated with a lower abundance of Megamonas, regardless of how a baby was fed (breastfed or formula fed). “While little is known about Megamonas in infancy, our previous research suggests there may be a link between this bacterium and asthma or respiratory viral infections, so vitamin D may offer additional benefits for childhood health that should be studied further,” added Dr. Kozyrskyj.

The researchers also assessed the association between infant and maternal vitamin D supplementation and the presence of Clostridioides difficile (C. difficile) in a baby’s gut. “Some infants carry the

diarrhea-causing bacterium C. difficile in their guts without any symptoms. However, when the levels of gut bacteria become imbalanced, this particular bacterium can multiply, causing illness and increasing the susceptibility to chronic disease later in childhood,” commented first author Kelsea Drall, an M.Sc. graduate from the University of Alberta and an AllerGen trainee.

The study found that nearly 30% of the infants carried C. difficile, but a lower incidence of the bacterium was observed among exclusively breastfed infants. However, neither infant supplementation with vitamin D drops nor maternal vitamin D supplementation during pregnancy or after delivery were associated with C. difficile colonization. “Interestingly, maternal consumption of vitamin D-fortified milk was the only factor that reduced the likelihood of C. difficile colonization in infants,” added Ms. Drall.

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