Probiotics keep hinting at protection from UTIs, but the proof stays thin

Probiotics are one of the most widely bought supplement categories, and the marketing routinely implies they defend against infection. Whether live bacteria genuinely help prevent or treat bacterial infections, from recurrent urinary tract infections to the stomach bug Helicobacter pylori, is a question the trial literature has answered only in fragments. This review set out to gather the recent randomised evidence across several infection types at once, including resistant bacterial colonisation, to see whether the signal is consistent and how much confidence it deserves.

The authors systematically reviewed 12 randomised controlled trials published between 2021 and 2026, covering single-strain and multi-strain probiotics used for recurrent urinary tract infections, Helicobacter pylori eradication, respiratory tract infections, acne vulgaris, and colonisation with multidrug-resistant bacteria. In total the trials included 1200 participants. Risk of bias was assessed with the Cochrane RoB 2.0 tool and the certainty of evidence was graded for every primary outcome. Because the trial designs and outcomes were too different to pool statistically, the team used a narrative synthesis with vote-counting instead of a formal pooled estimate.

The direction of benefit was consistent across most infection types. In two trials of recurrent urinary tract infections, 75% of probiotic users stayed recurrence-free against 33% on placebo. Three trials of Helicobacter pylori eradication reported success rates of 70 to 86%, and three respiratory infection trials reported symptom improvement of 64 to 96%. Two trials observed reductions in acne lesions. The exception was multidrug-resistant colonisation, where results across two trials were inconsistent. Crucially, the certainty of evidence was rated low to moderate for every outcome, mostly because the trials were small and imprecise.

This adds to a long-running pattern in probiotic research: repeated small trials pointing the same way without any single definitive study. The vote-counting approach used here can show direction but not size, so it cannot say how much benefit a probiotic actually delivers for any of these infections. It also leaves open which strains, doses and durations matter, since the included trials varied on all three. The authors are explicit that larger, standardised randomised trials are needed before probiotics could be routinely recommended for any of these uses.

If you already take a probiotic hoping it wards off infections, this review is mild encouragement rather than vindication: the recent trials lean in your favour across urinary, stomach and respiratory infections, but the evidence is too small and too varied to be trusted for any firm claim. If you do not take one, nothing here establishes that you are missing out. The most useful reading is as a progress report on a field that keeps showing promise without yet delivering proof.