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Could Your Kid’s Gut Health Be Impacting Their Allergies?

BC researchers have discovered a link between microbiome development and four childhood allergy disorders.

Michelle Gamage 19 Sep 2023The Tyee

Michelle Gamage is The Tyee’s health reporter. This reporting beat is made possible by the Local Journalism Initiative.

Four major childhood health conditions may be connected to the early development of a kid’s gut bacteria, according to researchers at the University of British Columbia and BC Children’s Hospital.

Kids who develop eczema, asthma, food allergies and/or hay fever may do so because the development of their gut microbiome was disrupted, according to the study published in Nature Communications. A gut microbiome is the micro-organisms and their genes within the gastrointestinal tract.

“We’re really excited about this study,” says Courtney Hoskinson, a PhD candidate at UBC and researcher who led the study. No other study has found a common origin for allergic diseases, she says.

These findings could be used to develop additional supplementation and general guidelines for clinicians to give to young children and their families as they grow up, Hoskinson says. Future guidelines might include encouraging of breastfeeding and nutrient-dense diets, encouraging kids to play outside so they can be introduced to beneficial bacteria while they grow, and discouraging any unnecessary use of antibiotics.

Understanding a common allergy cause could help doctors predict if a kid will develop allergies or help prevent them, which would have a huge impact considering one in three kids in Canada suffer from allergies, the study says.

Allergies have been on the rise over the past couple decades, Hoskinson says. This happened at the same time we as humans were changing our lifestyles in a way that is impacting our gut bacteria. So the study hypothesized there was a “correct recipe” for gut bacteria and that a disruption to that recipe could lead to allergies. They were right.

The study looked at clinical assessments of 1,115 children and followed their development from birth to age five. About half had no evidence of allergies at five years old and the other half were diagnosed by a doctor as having one or more allergies.

Kids without allergies had more than one negative allergy skin prick test, no history of wheezing and no diagnosis of allergic disorders such as eczema, asthma, inflammation inside the nose or food allergies.

Researchers then looked at samples of the children’s poop to examine their microbiome. Specifically, clinically collected stool samples when the kids were three months old and again at one year.

Researchers found kids who developed allergies had an imbalance of gut bacteria which led to inflammation within the gut.

“Typically, our bodies tolerate the millions of bacteria living in our guts because they do so many good things for our health,” Hoskinson says. “Some of the ways we tolerate them are by keeping a strong barrier between them and our immune cells and by limiting inflammatory signals that would call those immune cells into action.”

The immune system and gut microbiome develop at the same time, so looking at what happens in one may help us understand what’s going on in the other.

Previous studies found similarities in gut bacteria between people with food allergies.

“We’ve known for quite a while something really important in the microbiome was happening from birth to early toddlerhood,” says Ariangela Kozik, an assistant professor at the University of Michigan and co-founder and vice-president of the Black Microbiologists Association, who is not associated with the study or the lab that produced it.

Kozik says she’s “really excited” to see a study that shows how a fully matured or not fully matured bacterial “community” is linked to allergies.

As human infants develop, their immune system is hard at work learning what bacteria or pathogens should activate it, when it should turn off and what bacteria it should ignore, Hoskinson says.

Hoskinson refers to this process as the immune system learning new “recipes,” which are fed to it by the gut microbiome.

Researchers found if a child’s gut microbiome hadn’t developed in the same way a healthy’s child’s gut had, then “that irregular bacterial recipe interacts with our immune system and negatively impacts its outcomes,” Hoskinson says.

The study found that kids who had breast fed up to six months old, and kids whose parents self-identified as white were less likely to develop allergies.

Breast milk contains specific bacteria that helps a kid’s microbiome grow beneficial bacterial communities which can then fight off unhealthy ones, Hoskinson says.

As for how being white might help you reduce allergies, Hoskinson says it’s likely more to do with socioeconomic status and societal privilege than genes. Wealthier families are more likely to have access to green space and have work schedules that allow them to breastfeed — but more research is needed, she says.

The study also found babies who used antibiotics before they were one year old, who were assigned male at birth, or had parents with allergies were more likely to develop allergies.

Parents shouldn’t avoid antibiotics if their kid is sick, Hoskinson says — antibiotics save lives. But because antibiotics wipe out both the good and bad bacteria in a child’s gut, the decision to use antibiotics should be an “active conversation” between the doctor and family to “flush out whether antibiotics are absolutely necessary to avoid negatively impacting those beneficial bacteria,” she adds.

Allergies develop due to a combination of genetic predispositions and environmental exposures, Hoskinson says. “Even if a kid is exposed to the right bacteria they might develop the allergy anyway,” she says.

The study’s findings suggest that it’s not just the presence of a bacteria but what the bacteria is doing and producing while it's in our gut, Kozik says.

“Maybe interventions can focus on replacing that function or finding new ways to achieve the same function beyond just giving someone a probiotic, which is the go-to strategy right now,” Kozik adds.

Large-scale, long-term studies like this that study humans take a huge amount of commitment from scientists, participants and funders, Kozik says — so she says it’s thrilling to see the project properly conclude and for the researchers to be able to share what they found.

Hoskinson says next she hopes to work on larger studies that look at the allergies and gut microbiomes of children in developing countries or in mice.

“We’ve got a good starting point to say this is what is happening,” she says. “But we need more research to establish a correct bacterial recipe that could be related to these diseases and really nail down what we alluded to in this study.”  [Tyee]

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