A meta-analysis of 12 randomized, controlled trials, with a total of 3720 participants, examined the effectiveness and safety of probiotics in preventing acute upper respiratory tract infections (URTIs) in children, adults, and older people.
Probiotics, compared to placebo, were associated with fewer URTIs overall, shorter duration of URTI episodes, fewer antibiotic prescriptions, and fewer URTI-related school absences.
Probiotics appeared safe for use in these populations, as adverse events were similar between probiotic and placebo groups, and any reported probiotic side effects were minor (e.g. gastrointestinal symptoms).
Higher quality evidence would lend support to these findings in the future.
Quick M. (2015) Cochrane Commentary: Probiotics For Prevention of Acute Upper Respiratory Infection. Explore DOI: http://dx.doi.org/10.1016/j.explore.2015.07.012