Babies' diapers could be key to unlocking allergy mystery

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This article was published 23/3/2015 (1432 days ago), so information in it may no longer be current.

The poop in a baby's diaper could be key in determining whether he or she develops allergies in the future, says a team of Canadian scientists.

In a first-of-its-kind study, the scientists — some of whom are at the University of Manitoba — found that babies with fewer varieties of gut bacteria were more prone to develop food sensitivities — and, in some cases, allergies — by age one.

The research appeared in a recent edition of the journal Clinical and Experimental Allergy and was highlighted as the journal's "editor's choice." (The study's lead author says it's the first study to test infant gut bacteria's link to food sensitivities).

Scientists from the U of M and the University of Alberta analyzed the gut bacteria in the dirty diapers of 166 Manitoban babies. University of Toronto researchers James Scott and David Guttman used cutting-edge technology that sequenced the DNA of bacteria in the babies' fecal matter, collected when the kids were three months old and again when they were one year of age.

The same children were then tested at age one for food sensitivities to peanuts, eggs and milk using a skin-prick test. Those with a greater variety of gut bacteria were less likely to develop a skin irritation after the test.

The Canadian Institutes of Health Research and AllerGen NCE funded the study.

Study author Meghan Azad, an assistant professor in the department of pediatrics and child health at the U of M and researcher at the Children's Hospital Research Institute of Manitoba, says she didn't expect to find such a difference between gut-bacteria varieties and levels from baby to baby.

"They're all consuming breast milk or, maybe, formula. They stay at home all day, usually with their moms, but I was amazed at how different their microbiome profiles were," says Azad, a biochemist.

"That, in itself, was fascinating to me — to see how much variation there was already at three months of age."

Approximately six per cent of children have allergies, according to Health Canada. Peanut allergies, in particular, have made headlines in recent years for their increasing prevalence and virulence.

At the same time, gut bacteria — or the gut microbiome — has also attracted the attention of scientists, who now understand that so-called good bacteria play a key role in disease prevention. (Yogurt companies have used this science to sell their products as "probiotic.")

"All these microbes blooming in us and on us are doing a lot of important things that we never knew about until the technology was developed," says Azad, who notes that studying the gut microbiome in infants is important since it seems to be established early and may predict and even prevent future allergies.

"What is a healthy microbiome in early life, and at what pace does it develop, and where are the windows where we have a chance to intervene?" says Azad, who plans to ask those questions in future studies.

The study is part of the larger Canadian Healthy Infant Longitudinal Development (CHILD), in which scientists are following 3,500 families, tracking their biological and lifestyle factors and prevalence of allergies over years.

Scientists believe that an allergy occurs when the immune system malfunctions.

"It's reacting to something harmless, like a food, when it should only be reacting to something that could make us sick," says Azad.

Evidence suggests that an obsession with hygiene is partially to blame for a decrease in gut flora and an increase in allergies.

"If we're too clean and too sterile, babies aren't exposed to those everyday microbes and their immune systems don't learn properly what is a scary microbe that deserves a protective reaction versus what is a harmless substance that isn't a risk," says Azad.

The study's lead author, U of A epidemiologist Anita Kozyrskyj, says other factors contributing to a reduction in gut flora include the overuse of antibiotics and an increase in non-vaginal deliveries.

"Infants' gut microbiotics are seeded from the mom, so it's from the mom's vaginal and gut microbiota and breast-milk microbiota too," says the Edmonton-based Kozyrskyj, who earned her post-graduate degrees at the U of M.

Kozyrskyj says the cost of DNA sequencing has dropped since her team began its research in 2010, making gut-bacteria levels more likely to be used as a biomarker for disease and allergies.

"So I imagine in the future there will be kind of a test — a custom sort of diagnostic test, a predictive test with this technology and infant poop."

 

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