Design: Phase 3, randomised, double-blind, placebo (autologous)-controlled
Population: 448 adults with moderate-to-severe IBS at five Norwegian hospitals
Primary outcome: IBS-SSS reduction ≥75 points at 90 days
Effect: 40% vs 38%; difference 1.9 points (95% CI −8.1 to 12.0), P=0.76

REFIT2 enrolled 450 adults aged 18–65 with moderate to severe irritable bowel syndrome (Rome IV) at five Norwegian hospitals. They were randomised 2:1 to a single enema of donor faeces or of their own faeces as placebo, with everyone masked.

At 90 days, 40% in the donor group and 38% in the placebo group had a clinically meaningful fall in symptom score (difference 1.9 points, 95% CI −8.1 to 12.0). Adverse events were similar.

Earlier, smaller trials had raised hopes. This larger, well-masked trial found no benefit, and the 38% placebo response is a reminder of how often IBS improves on its own or with attention. Patients asking about faecal transplant for IBS can be told it has not been shown to work.

Faecal microbiota transplant is not a treatment for irritable bowel syndrome on current evidence.
Nearly four in ten improved with their own faeces — placebo response in IBS is large.
Patients seeking private or home faecal transplant for IBS should be advised against it.
Faecal transplant still has an established role in recurrent C. difficile infection, which this trial did not address.

Why it matters

Interest in the microbiome has run ahead of evidence in IBS, and this is the largest test so far.

The statistics, in plain English

The confidence interval of −8.1 to 12.0 percentage points includes zero, so the trial found no benefit; it also rules out a large benefit, since the upper limit is about 12 points.