Researchers have found a causal link between caesarean section birth, low intestinal microbiota and peanut sensitivity in infants. They report the effect is more pronounced in children of Asian descent than others in a recently published paper in the journal of the American Gastroenterological Association.
“It’s important to know what predicts or increases (the) risk of food sensitivities because they predict which infants will go on to develop asthma and other types of allergies,” said Anita Kozyrskyj, pediatrics professor in the Faculty of Medicine & Dentistry and adjunct professor in the School of Public Health.
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.
The infants were given skin prick tests at one and three years of age to assess their reaction to various allergens, including egg, milk and peanut. The babies with low Bacteroides levels were found to have a threefold increase in their risk of developing a peanut sensitivity by age three – and the risk was eight times higher for babies born to mothers of Asian descent.
The team did further statistical analysis to look for what are known as mediation or causal effects between the exposure and the outcome. “In this case, we observed that there was an association between Asian ethnicity and peanut sensitivity, and then the mediation analysis provided additional evidence for the causal association with caesarean section,” explained Kozyrskyj, noting it is the first study to identify this link.
The researchers also observed that infants with low Bacteroides also had lower levels of sphingolipids, proteins that are key to cell development and signalling in many parts of the body, including the immune system. Gut microbiota are the main source of these proteins. Children who have this deficiency in their immune cells may be more likely to develop food allergies, Kozyrskyj said.
“As the gut microbiota are developing, so is the gut’s immune system, training the gut to react to pathogens and to be tolerant of the food that we require,” she explained.
Half a million Canadian children have a food allergy, while peanut allergy affects about two in 100 and can lead to severe anaphylaxis. Babies who have food allergies are at greater risk of developing asthma, wheezing, eczema and allergic rhinitis later in life, the study authors reported.
The overall rate of allergies is increasing in Western countries and is likely linked to environmental factors, said Kozyrskyj, who is principal investigator of the SyMBIOTA (Synergy in Microbiota) laboratory, which studies the impact of maternal and infant antibiotic use, birth mode and breastfeeding on the composition of the intestinal microbiota in infants.
“In China, food allergies are uncommon, but those who immigrate to Canada face a higher risk and more severe form of allergic disease,” she said. “It’s likely related to a change in diet and environment.”
The next step for the research is for the results to be replicated in other studies worldwide, Kozyrskyj said. She praised her main collaborator Hein Tun, a former post-doctoral fellow at U of A who is now an assistant professor of public health at the University of Hong Kong.
Previous research by Kozyrskyj and others has shown that babies born by caesarean section don’t get the same beneficial transfer of microbiota from mother to child that infants born through vaginal delivery receive. Studies looking to mitigate this by giving C-section babies probiotics or even swabbing them with their mother’s vaginal bacteria have not been as successful as hoped, Kozyrskyj said.
The best path is to avoid caesarean birth unless it’s medically necessary. “With this evidence at hand, the parent and the obstetrician might choose a different birth mode,” she said.
| By Gillian Rutherford for Troy Media
This article was submitted by the University of Alberta’s Folio online magazine. The University of Alberta is a Troy Media Editorial Content Provider Partner.
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