Treatments · Diet
Low FODMAP diet
What ACG 2021, BSG 2021 and NICE say about low fodmap diet for IBS, with the studies, trials, news, and stories we have tagged to it.
What the guidelines say
| Body | Position | Strength and evidence | Source |
|---|---|---|---|
| ACG 2021 | Recommends a limited trial of a low FODMAP diet in patients with IBS to improve global symptoms. | Conditional recommendationVery low quality of evidence | PubMed |
| BSG 2021 | Describes a low FODMAP diet as a second-line dietary therapy for global symptoms and abdominal pain, to be supervised by a trained dietitian, with FODMAPs reintroduced according to tolerance. | Weak recommendationVery low quality of evidence | PubMed |
| NICE | If symptoms persist after general lifestyle and dietary advice, offer further dietary management including single-food avoidance and exclusion diets such as a low FODMAP diet, given only by a healthcare professional with expertise in dietary management. | Not graded | Source |
FODMAPs are fermentable oligosaccharides, disaccharides, monosaccharides, and polyols: short-chain carbohydrates (in foods such as wheat, onions, garlic, legumes, lactose-containing dairy, some fruits, and sugar alcohols) that are poorly absorbed in the small intestine. They draw water into the gut and are fermented by colonic bacteria, which is thought to drive bloating, pain, and altered stool form in people whose gut is more sensitive to distension. The diet restricts these carbohydrates for a limited period, then reintroduces them group by group to find individual triggers, then settles into a personalised, less restrictive pattern PMID 29336079.
The strongest pooled evidence is a 2022 network meta-analysis of 13 randomised trials (944 patients), in which a low FODMAP diet ranked first for global symptoms against habitual diet and was superior to standard British Dietetic Association/NICE dietary advice for bloating; the authors note that most trials were in secondary or tertiary care and did not study reintroduction or personalisation PMID 34376515. An earlier 2018 meta-analysis of seven trials (397 participants) also found reduced global symptoms, but graded the overall evidence as very low quality and observed that the trials with the most rigorous control diets showed the smallest effects PMID 30046155. In one well-controlled UK trial using a sham diet of matched difficulty, 57% on the low FODMAP diet reported adequate relief versus 38% on the sham diet, a difference that did not reach statistical significance in the intention-to-treat analysis, and stool Bifidobacterium levels fell on the low FODMAP diet PMID 28625832.
Points clinicians commonly raise: the restriction phase is meant to be short, not a permanent way of eating, and the reintroduction phase is where most of the practical value is thought to lie PMID 29336079; all three guidelines frame it as a second step after general dietary advice, delivered with dietitian support PMID 33903147; and the effect on gut bacteria over longer periods is not well characterised PMID 28625832.
Talk to a clinician before starting or stopping anything.
References
- 1Lacy BE, Pimentel M, Brenner DM, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2021. PMID 33315591
- 2Vasant DH, Paine PA, Black CJ, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021. PMID 33903147
TreatIBS is an informational site and does not provide medical advice. The research summarized here may not apply to your situation. Talk with a clinician before starting, stopping, or changing any treatment.
Studies
Recent PubMed entries tagged to Low FODMAP.
Trials
Registered interventional studies tagged to this approach.
The Stool Microbiome of Treated and Untreated IBS (Irritable Bowel Syndrome) Patients
Low FODMAP dietary regimen
A Study Evaluating the Impact of Regular FODMAP-targeting Digestive Enzyme Blend Use on Gastrointestinal Symptoms in Individuals With Self-Reported Bloating
FODMAP-targeting digestive enzyme blend, Placebo
The Role That Food and Bacteria Play in Generating Abdominal Pain
FODMAP Challenge
Evaluating the Added Benefit of Osteopathic Care to a Flexi-FODMAP Diet in Fibromyalgia Patients With Irritable Bowel Syndrome
Osteopathic care, Sham Osteopathic care, Flexi-FODMAP Diet
Mechanism of FODMAP Restriction on FGID Patients
Low FODMAP diet, Gentle FODMAP diet, Traditional Dietary Advice
Exclude or Expose in Irritable Bowel Syndrome: What Works for Whom and How?
FODMAP Diet, Exposure-based Cognitive Behavioral Therapy
Efficacy of the DOMINO Diet App in IBS
Dietary intervention: DOMINO app, Dietary intervention: low FODMAP diet
Efficacy of a Low FODMAP Diet in the Absence of Lactose Malabsorption in Moderate to Severe ROME IV IBS.
FODMAP diet
Low FODMAP Plus PEG 3350 for the Treatment of Patients with Irritable Bowel Syndrome-Constipation
Low FODMAP diet/PEG 3350, sham diet/PEG 3350
News
Headlines that mention this approach, linked to the original.
Letter to the Editor Re: A Randomized Trial of Rifaximin vs Low FODMAP Diet
We read with interest the report by Lee and colleagues.
Low Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols Diet vs Traditional Dietary Advice in Postprandial Functional Dyspepsia: A Randomized Clinical Trial
Postprandial distress syndrome affects 80% of individuals with functional dyspepsia, yet evidence-based dietary management strategies remain poorly defined.
Stories
Public accounts from people who tried it, labeled as individual experience.
Three years into low FODMAP: Becky Excell on what the diet did and did not change
Reported the diet helped her identify specific triggers (garlic, onion, gluten) and improved symptoms partly, then plateaued; she still has symptoms, which she links to stress and to some foods classed as low FODMAP.
Carley Adolf: weekly FODMAP reintroduction trials on a vegan diet
Reported that blackberries, beans and dark chocolate chips passed with no change in energy or digestion, while apple juice and a whole apple left her overly full, tired and unsettled for a day or two; very ripe bananas caused immediate upper-stomach pain.
Ten years of IBS-D: David (IBSWithWatson) on diet, nortriptyline, therapy and hypnotherapy
Reported that no single change resolved his IBS-D; combining identified food triggers, short-term symptom medication, nortriptyline, therapy, hypnotherapy and gradually facing avoided situations left him able to work, travel and socialise, with flare-ups still occurring.
Sam Runs Now: low FODMAP with a dietitian, then getting stuck in the personalisation phase
Reported that nausea, appetite loss, weekly headaches and fatigue eased about four weeks into elimination; reintroduction pointed to fructans, lactose, mannitol and sorbitol; staying restricted too long brought food anxiety, so he is now widening his diet with a second dietitian.
Woodie & Marie: three years on low FODMAP and the struggle to reintroduce foods
Reported that the low FODMAP diet calmed her symptoms enough that she was reluctant to reintroduce foods; unmeasured reintroduction attempts failed, measured monthly trials have added back only a few foods, and eating garlic bread and legumes over the holidays triggered a multi-day flare.
Critiques
Single-study critiques that cover this approach.
Low FODMAP vs traditional IBS dietary advice: the Swedish head-to-head trial
Böhn et al. randomised 75 Swedish IBS patients to four weeks of low FODMAP or traditional dietary advice. Both groups improved, with no difference between them. A careful read of what that does and does not show.