Researchers have found a causal link between cesarean birth, weak gut microbiota, and peanut sensitivity in infants, and they report that the effect is more pronounced in children of Asian origin than others, in an article recently published in the journal of the American Gastroenterological Association.
“It’s important to know what predicts or increases the risk of food sensitivity, because they predict which infants will develop asthma and other types of allergies,” said Anita Kozyrskyj, professor of pediatrics at the school of medicine and of Dentistry from the University of Alberta and Adjunct Professor. at the School of Public Health.
The research team analyzed gut bacteria from 1,422 infants in the CHILD cohort study, examining fecal samples taken at three or four months and again at one year. They identified four typical trajectories for bacterial development, including one in which infants had consistently low levels of Bacteroides, a type of bacteria known to be essential for the development of the immune system. This profile was most common in babies born by cesarean section.
Infants underwent skin tests at one and three years of age to assess their reaction to a variety of allergens, including egg, milk and peanuts. Babies with low levels of Bacteroides were three times more likely to develop peanut sensitivity by age three – and the risk was eight times higher for babies born to mothers of Asian descent.
The team performed a more in-depth statistical analysis to look for what is known as “mediation” or causal effects between exposure and outcome. “In this case, we observed that there was an association between Asian ethnicity and peanut sensitivity, and then the mediating analysis provided further evidence of the causal association with cesarean section,” explained Kozyrskyj, noting that this was the first study to identify this link.
Researchers also observed that infants with low Bacteroides also had lower levels of sphingolipids, proteins that are essential for cell development and signaling in many parts of the body, including the immune system. The gut microbiota is 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 grows, the gut’s immune system develops, causing the gut to respond to pathogens and tolerate the food we need,” she explained.
Half a million Canadian children have a food allergy, while peanut allergy affects about two in 100 children 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, principal investigator of the SyMBIOTA (Synergy in Microbiota) laboratory, which studies the impact of the use of antibiotics on the mother. and the infant, the mode of birth and breastfeeding. on the composition of the gut microbiota in infants.
“In China, food allergies are rare, but those who immigrate to Canada face a higher risk and a more severe form of allergic disease,” she said. “It’s probably related to a change in diet and environment.”
The next step in the research is to replicate the results in other studies around the world, Kozyrskyj said. She congratulated her main collaborator Hein Tun, a former postdoctoral fellow at the U of A who is now an assistant professor of public health at the University of Hong Kong. Their research was funded by the Canadian Institutes of Health Research, Alberta Innovates and the Allergy, Genes, and Environment (AllerGen) network. Kozyrskyj is a member of the Research Institute for Women’s and Children’s Health. Funding partners for the CHILD cohort study include the Stollery Children’s Hospital Foundation and the Alberta Women’s Health Foundation through the Women and Children’s Health Research Institute.
Previous research by Kozyrskyj and others has shown that babies born by cesarean section do not achieve the same beneficial transfer of microbiota from mother to child as infants born through vaginal birth. Studies to alleviate this by giving babies caesarean sections probiotics or even dabbing them with their mother’s vaginal bacteria haven’t been as successful as expected, Kozyrskyj said.
The best way is to avoid a cesarean delivery unless it is medically necessary. “With this evidence at hand, the parent and obstetrician could choose a different mode of birth,” she said.