The short version
- Across ten randomised trials in 1,030 people, peppermint oil beat placebo for global IBS symptoms with a relative risk of not improving of 0.65 and a number needed to treat of 4, on evidence the authors graded as very low quality.
- Peppermint oil caused significantly more adverse events than placebo in that meta-analysis, at a relative risk of 1.57, with reflux the characteristic complaint.
- A meta-analysis of 53 probiotic trials in 5,545 IBS patients concluded that which combinations, species or strains work remains, for the most part, unclear.
- In 106 people whose IBS-diarrhoea followed a gut infection and who had raised intestinal permeability, 79.6% responded to 5 g of glutamine three times daily against 5.8% on placebo, in a single-centre trial its own authors said needs validating.
- In the CARIBS trial, 76% of people on a low-FODMAP diet plus dietary advice responded at four weeks against 58% on optimised medical treatment.
Before any of this: irritable bowel syndrome is a medical diagnosis, and it is a positive one, made against the Rome IV criteria after coeliac disease has been excluded by serology. It is not a label you give yourself because your stomach is difficult. Please get diagnosed. Everything below assumes you already have been, and none of it treats, cures or prevents anything — supplements do not do that, and any brand telling you otherwise is telling you something the regulator would not let it print.
With that said, here is what happens when you sort the IBS aisle by how much evidence each item is actually carrying.
The one with a meta-analysis
Ingrosso and colleagues pooled ten randomised controlled trials in 1,030 patients. Peppermint oil beat placebo for global IBS symptoms, with a relative risk of not improving of 0.65 (95% CI 0.43–0.98) and a number needed to treat of 4. For abdominal pain the relative risk of not improving was 0.76 and the number needed to treat was 7.
Now the two parts that the ads leave out. Adverse events were significantly more common on peppermint oil than placebo (RR 1.57, 95% CI 1.04–2.37), and gastro-oesophageal reflux was singled out by the reviewers as its own safety outcome. And the authors graded the quality of the evidence as very low, and closed by asking for adequately powered trials of peppermint oil as a first-line treatment, which is not how you write about a settled question.
That is still, by some distance, the best-evidenced thing you can buy without a prescription for this. Notice the confidence interval on that number needed to treat: 2.5 to 71. Somewhere between one person in every two or three, and one in seventy-one.
Probiotics: real, but nobody can tell you which one
Ford and colleagues pooled 53 randomised trials of probiotics in 5,545 IBS patients. Particular combinations, species and strains appeared to benefit global symptoms and abdominal pain — and the authors stated that it was not possible to draw definitive conclusions, and that which strains work "remains, for the most part, unclear."
Read that as a purchasing instruction rather than a disappointment. The category works in aggregate and the individual product in your hand may or may not be one of the ones that did. Data for prebiotics and synbiotics in the same review were described as sparse. The one clearly effective agent in that paper was rifaximin, an antibiotic, at a relative risk of symptoms persisting of 0.84 — and that is a prescription and a conversation, not a shelf item.
The result that is too good, in a population too narrow
Glutamine deserves a paragraph because of how often it gets quoted out of its box. Zhou and colleagues randomised adults who had developed diarrhoea-predominant IBS after an enteric infection, and who had measurably increased intestinal permeability, to 5 g of glutamine three times daily or placebo for eight weeks. The primary endpoint — a fall of at least 50 points on the IBS severity score — was met by 79.6% on glutamine and 5.8% on placebo. Permeability normalised in the glutamine group.
A fourteen-fold difference is not a normal trial result. It is either a genuinely large effect in an unusually well-selected group, or something about a single-centre study, and the authors themselves called for large trials to validate it. Either way it applies to people whose IBS started after a gut infection and who have documented hyperpermeability. If that is not you, this study is not about you.
Where enzymes fit, and where they do not
Digestive enzymes are not an IBS treatment and we are not going to pretend otherwise. What they are is the answer to a different question that frequently hides inside an IBS diagnosis: a specific sugar you cannot break down. Lactose is the obvious one, and it is worth remembering that the AGA workup puts carbohydrate enzyme deficiency near the top of the list precisely because it is common and it masquerades.
So the honest use case for a blend like ours is narrow and it is real: you have a named food that reliably causes trouble within an hour or two, and you want to match a tool to it. If you cannot name the food, an enzyme blend is a subscription to a guess.
The intervention that beat the drugs
The largest recent head-to-head is worth more than most of the supplement literature combined. In CARIBS, 294 people with moderate-to-severe IBS were randomised to a low-FODMAP diet plus traditional dietary advice, a low-carbohydrate diet, or optimised medical treatment chosen for their predominant symptom. At four weeks, 76% of the diet-plus-advice group had responded, against 71% on low-carbohydrate and 58% on optimised medication (p = 0.023).
Diet beat drugs. Diet also beat every supplement in this article, and it is free. The low-FODMAP diet is a three-stage protocol rather than a permanent way of eating, which is a distinction worth getting right before you start.
The other clinically real thing here is not a capsule at all. Gut-directed hypnotherapy, cognitive behavioural therapy, diaphragmatic breathing and central neuromodulators all appear in the AGA's advice for these symptoms. That is the gut-brain axis being used as medicine, and it is further ahead than anything being sold as a gut-brain supplement.
What we would actually tell you
Get the diagnosis. Do the diet work with a dietitian if you can get one. If you want to try one thing off a shelf, make it enteric-coated peppermint oil, give it four weeks, and stop if you get reflux. Judge it on one symptom you can name — not on a general feeling that things are better, which is exactly what a placebo produces.
Good questions
Does peppermint oil actually work for IBS?
Yes, modestly, and it is the best-evidenced thing on the shelf. Pooling ten trials in 1,030 people gave a number needed to treat of 4 for global symptoms, though the confidence interval ran from 2.5 to 71 and the authors rated the evidence very low quality. Side effects were more common than on placebo. Enteric-coated capsules, four weeks, stop if you get reflux.
Which probiotic strain should I buy for IBS?
Nobody can honestly tell you. The 2018 meta-analysis of 53 trials in 5,545 patients found that particular strains and combinations appeared to help, then stated that which ones remains, for the most part, unclear. Buy a product that names its strains so you can at least look them up, give it four weeks, and judge it on one symptom rather than a general sense of improvement.
Should I take glutamine for IBS?
Only if your IBS started after a gut infection and you have documented increased intestinal permeability. That is the exact population in the trial that produced the striking 79.6% versus 5.8% result, and a fourteen-fold difference from one single-centre study is a reason for caution as much as excitement. Outside that group, there is no trial telling you it does anything.
Can digestive enzymes treat IBS?
No. Enzymes address a named carbohydrate you cannot break down, which is a different problem that often hides inside an IBS diagnosis. If a specific food reliably causes trouble within an hour or two, matching an enzyme to it is reasonable. If you cannot name the food, you are buying a guess with a subscription attached.
Is it worth seeing a dietitian instead of buying supplements?
Almost certainly, and this is the least profitable sentence on this page. In the CARIBS trial, structured dietary work produced a 76% response rate at four weeks against 58% for optimised medication, which beats anything in the supplement aisle. Dietitian-led delivery is also what makes the low-FODMAP protocol safe, because the restriction phase is meant to end.
How do I know it is IBS and not something else?
You do not, from home. IBS is a positive diagnosis made against the Rome IV criteria with coeliac disease excluded by blood test, and coeliac disease is common enough that skipping that step is a genuine risk. Alarm features such as bleeding, weight loss, or symptoms waking you at night change the picture entirely. Get diagnosed before you start treating.
Sources
- Ingrosso MR, Ianiro G, Nee J, Lembo AJ, Moayyedi P, Black CJ, Ford AC. Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome. Aliment Pharmacol Ther, 2022. View study
- Ford AC, Harris LA, Lacy BE, Quigley EMM, Moayyedi P. Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome. Aliment Pharmacol Ther, 2018. View study
- Zhou Q, Verne ML, Fields JZ, Lefante JJ, Basra S, Salameh H, Verne GN. Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut, 2019. View study
- Nybacka S, Törnblom H, Josefsson A, et al. A low FODMAP diet plus traditional dietary advice versus a low-carbohydrate diet versus pharmacological treatment in irritable bowel syndrome (CARIBS): a single-centre, single-blind, randomised controlled trial. Lancet Gastroenterol Hepatol, 2024. View study
- Moshiree B, Drossman D, Shaukat A. AGA Clinical Practice Update on Evaluation and Management of Belching, Abdominal Bloating, and Distention: Expert Review. Gastroenterology, 2023. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
