Donor Stool Transplants Came Up Short in Irritable Bowel Syndrome

CATEGORY: GUT & DIGESTIVE HEALTH

If you live with irritable bowel syndrome, you’ve probably run into the promise that fixing your gut bacteria could fix your gut. The most rigorous test of that idea has now reported, and the promise didn’t hold. Among 450 Norwegian adults with moderate-to-severe IBS, 40% improved after receiving a stool transplant from a healthy donor. On placebo, 38% improved. That gap of 1.9 percentage points is statistically no difference at all.¹

A Placebo Made From the Patient’s Own Stool

The trial, called REFIT2, ran at five hospitals in Norway and enrolled adults aged 18 to 65 whose symptoms rated moderate to severe on a standard questionnaire. Two of every three participants received a fecal microbiota transplantation, a medically processed stool sample from a healthy donor, given once by enema. The rest got a convincing fake: their own stool, processed identically and returned to them. A random draw decided who got which. Nobody knew the answer during the trial, not the patients, not their doctors, not the people scoring the results. That’s about as clean as blinding gets in this field.

Two Points Apart After Ninety Days

Success was defined up front as a drop of at least 75 points on the IBS Severity Scoring System, a questionnaire adding up pain, bloating, bowel habit and how much daily life is disrupted. Ninety days after treatment, 119 of 299 people in the donor group had cleared that bar, against 57 of 151 in the placebo group. Forty percent versus 38%. Side effects were about equally common in both groups. The authors put their conclusion plainly: changing the gut’s microbial mix by itself might simply not be enough to relieve IBS.

The Bigger Trial Their Own Earlier Study Asked For

This result lands hard because of who produced it. In 2018, the same Norwegian research network ran a 90-person, single-hospital trial and found a real benefit: 65% of transplant recipients improved, versus 43% on placebo. Those authors wrote that larger, multicentre studies were needed to confirm the finding.² REFIT2 is that confirmation study, five times the size, and the benefit vanished. A separate Norwegian trial in 2020 also reported success, using stool from one carefully selected donor, which kept alive the idea that the right donor is the secret ingredient.³ The new trial used several healthy donors and a simpler enema delivery, so questions about donors and dosing do remain open. What’s no longer open is whether an ordinary healthy-donor transplant reliably treats IBS. It doesn’t. For recurrent C. difficile, a dangerous gut infection, stool transplants remain a proven and approved treatment. This verdict applies to IBS.

Key Takeaways

• Improvement rates were nearly identical with donor stool and with placebo: 40% versus 38%, a gap small enough to be pure chance.
• The placebo was each patient’s own stool, so neither expectation nor the procedure itself can explain the result away.
• The same network’s smaller 2018 trial was positive; this was the larger confirmation it called for, and it didn’t confirm.

References

1. Johnsen PH, Juul FE, Hoff DAL, et al. Faecal microbiota transplantation in irritable bowel syndrome (REFIT2): a randomised, double-blind, placebo-controlled, phase 3 trial. The Lancet. 2026;S0140-6736(26)01424-8. link
2. Johnsen PH, Hilpüsch F, Cavanagh JP, et al. Faecal microbiota transplantation versus placebo for moderate-to-severe irritable bowel syndrome: a double-blind, randomised, placebo-controlled, parallel-group, single-centre trial. The Lancet Gastroenterology & Hepatology. 2018;3(1):17–24. link
3. El-Salhy M, Hatlebakk JG, Gilja OH, Kristoffersen AB, Hausken T. Efficacy of faecal microbiota transplantation for patients with irritable bowel syndrome in a randomised, double-blind, placebo-controlled study. Gut. 2020;69(5):859–867. link