The systematic review and meta-analysis, pooled data from more than 4,800 in 20 clinical trials across the globe, finding that the rate of asthma diagnosis was not significantly different between children whose mothers either took probiotics during pregnancy or gave probiotics to them as babies in the first year, and those that did not.
Led by Meghan Azad, from the University of Alberta, the team revealed the rate of doctor-diagnosed asthma was 11.2% among infants who received probiotics and 10.2 % among babies who received placebo.
"Taking probiotics had no effect on the asthma rate," commented Azan. "We haven't shown there's any harm in giving probiotics, but it can't really be advised as a strategy to prevent asthma."
"That doesn't mean probiotics aren't good for other reasons," she added. "There's really good evidence that probiotics are beneficial to infants who are born pre-term and suffer from a bowel condition. There's also good evidence that probiotics might prevent eczema."
The team identified 20 eligible trials including data from 4866 children in which probiotics or placebo were given mothers during pregnancy or to infants during the first year of life. Only five trials conducted follow-up beyond participants’ age of 6 years, with an average follow up of 24 months. None of the trials were powered to detect asthma as the primary outcome.
Azad and her team reported that among 3257 infants enrolled in nine trials contributing asthma data, the risk ratio of doctor diagnosed asthma in participants randomised to receive probiotics was 0.99, while the risk ratio of incident wheeze was 0.97.
"Randomised controlled trials to date have not yielded sufficient evidence to recommend probiotics for the primary prevention of these disorders," stated the team.
However, Azad and her team also revealed another finding that warrants more research: babies who received probiotics as infants or in utero had higher incidences of lower respiratory infections.
"This study identified a potential association between probiotics and lower respiratory infections," said Azad. "But more research is required to see if the two are indeed linked."
She added that the topic of research is important because "it summarised an emerging area of research, and will help physicians make evidence-based decisions relating to childhood asthma prevention."
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Source: British Medical Journal
Published online ahead of print, doi: 10.1136/bmj.f6471
"Probiotic supplementation during pregnancy or infancy for the prevention of asthma and wheeze: systematic review and meta-analysis"
Authors: Meghan B Azad, J Gerard Coneys, et al