The concept of probiotic therapy is a compelling one: under duress from illness or adverse effects from medications, the gastrointestinal biome becomes altered. Orally repleting this biome to restore “normal balance” ought to improve morbidity. Sounds good, right? Unfortunately, plausibility is not the same as practical efficacy.
Other indications or specific contexts notwithstanding, this multi-center trial shows probiotics confer no advantage for progression of gastroenteritis in children. These authors conducted a randomized, double-blinded trial in six pediatric Emergency Departments in Canada, including 886 children presenting with fewer than 72 hours of infectious diarrheal symptoms. They each received a 5-day course of either Lactobacillus rhamnosus R0011 and L. helveticus R0052 or placebo. Short answer: about 25% of each cohort progressed to moderate-to-severe gastroenteritis, and the duration of diarrhea was a little over two days, regardless.
The authors note “5 out of 12 leading guidelines endorse the use of probiotics”, although it does not appear they have a citation regarding how many dentists would recommend. While these data do not generalize to all indications, nor potentially all possible probiotic formulations, these data certainly tilt the board away from “potentially useful” towards “probably not useful”. Adverse events were common and similar between groups, so probiotics are unlikely to be harmful in a population with normal baseline health status – but you might as well just visualize your money concurrently swirling along down the toilet.
“Multicenter Trial of a Combination Probiotic for Children with Gastroenteritis”