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Low FODMAP Diet Guide

The best-researched diet for irritable bowel syndrome (IBS), made practical. See what the trials found, check it's right for you, find out which foods are low FODMAP, test your triggers with the reintroduction planner, and cook from 27 gut-friendly recipes.

Low FODMAP is a short-term diet for diagnosed IBS, not a lifelong one. Before you start, see your GP to rule out other conditions, and get tested for coeliac disease while you're still eating gluten. Read the safety checks →

What are FODMAPs?

FODMAPs are a group of short-chain carbohydrates (sugars and fibres) that the small intestine absorbs poorly. They pass into the large bowel, where they draw in water and are fermented by gut bacteria, making gas.

For most people that's harmless, and even good for gut bacteria. But people with IBS often have a more sensitive gut, so the extra water and gas stretch the bowel and cause bloating, pain, wind, and diarrhoea or constipation.

The diet was developed at Monash University in Melbourne. It isn't about cutting foods forever. You lower FODMAPs for a few weeks, then bring them back one group at a time to find your triggers.

F
Fermentablebroken down by gut bacteria, producing gas
O
Oligosaccharidesfructans (wheat, onion, garlic) and GOS (legumes)
D
Disaccharideslactose (milk, yoghurt, ice cream)
M
Monosaccharidesexcess fructose (honey, apples, mango)
A
And
P
Polyolssorbitol and mannitol (stone fruit, mushrooms, sugar-free gum)

What does the research actually show?

Low FODMAP is the most studied diet for IBS, with dozens of randomised trials. But it isn't magic, and it has downsides. Tap a topic to open it.

Strong consistent results from randomised trials Moderate good trials, some limits Promising smaller or early trials Caution known downsides
Halmos et al., 2014 — Gastroenterology (Monash University)
Randomised, single-blind crossover trialn = 30 with IBS + 8 healthy controls21 days on each diet

All meals were provided. On the low FODMAP diet, about 70% of people with IBS had lower overall symptom scores than on a typical Australian diet, with less bloating, pain and wind. The biggest improvement came within the first 7 days. People without IBS noticed no difference.

van Lanen et al., 2021 — European Journal of Nutrition
Meta-analysis12 controlled trials in adults

The low FODMAP diet reduced IBS severity to a "moderate-to-large" extent compared with control diets. On the standard IBS Symptom Severity Score (0–500), it averaged 45 points lower, and quality of life improved. Results were similar across IBS types, ages and diet lengths.

Cuffe et al., 2025 — Lancet Gastroenterology & Hepatology
Network meta-analysis28 randomised trials, 2,338 people11 diets compared

Compared with people's usual diet, low FODMAP roughly halved the risk of symptoms not improving (relative risk 0.51), with moderate-certainty evidence. It had by far the most evidence of any diet tested. It was the only well-studied diet that clearly beat a normal diet for bloating, and it also helped abdominal pain. It did not reliably change bowel habits.

Takeaway: if you have IBS, a properly done low FODMAP diet gives you a good chance of real relief, especially from bloating and pain. Expect to know within 2–6 weeks whether it's working.
Rej et al., 2022 — Clinical Gastroenterology and Hepatology
Randomised controlled trialn = 99 with IBS (diarrhoea or mixed)4 weeks

This trial compared "traditional" IBS advice (regular meals, less fat, caffeine, alcohol, spicy food and gas-forming foods), low FODMAP and gluten-free. Symptoms improved in 42%, 55% and 58% of people respectively. The differences weren't statistically significant, and people found the traditional advice cheaper and easier.

That's why both the British Society of Gastroenterology (2021) and the American College of Gastroenterology (2021) guidelines place low FODMAP as a second step. Try simple first-line advice first, then move to low FODMAP with a dietitian if symptoms continue. The ACG suggests "a limited trial".

Takeaway: if you haven't already, try regular meals, less caffeine, alcohol and fatty or spicy food for a few weeks. If that isn't enough, low FODMAP is the next, best-studied step.
Staudacher et al., 2022 — Neurogastroenterology & Motility (King's College London)
Follow-up studyn = 1812 months

People who went through all three steps (restriction, reintroduction and a personalised diet) were followed for a year. Adequate symptom relief rose from 28% at the start to 67% at 12 months, and symptom scores fell significantly. Importantly, beneficial Bifidobacteria numbers were back to their starting levels.

Takeaway: the goal is the most varied diet you can eat comfortably, not strict low FODMAP forever. Small study, but the direction is encouraging.
Wilson, Cox & Whelan, 2020 — Proceedings of the Nutrition Society (review)
Review of the evidence

Gut bacteria: strict restriction lowers Bifidobacteria, a beneficial group that feeds on FODMAPs. Nutrition: cutting grains, fruit and dairy can lower fibre and calcium. Not everyone responds: about 50–80% do, so 20–50% get no benefit even when they follow it well. It's complex: results are better when a dietitian teaches the diet than when people follow a handout.

Reintroducing foods (Step 2) largely fixes the fibre and gut bacteria problems. That's why the strict stage should last 2–6 weeks, not months. If you've had no improvement after 4–6 weeks of doing it properly, stop and talk to your doctor or dietitian about other options, such as gut-directed hypnotherapy or medication.

Takeaway: used as a short diagnostic tool, the risks are small. Used as a permanent restrictive diet, they grow.
Cox et al., 2020 — Gastroenterology (King's College London)
Randomised, blinded trial vs sham dietn = 52 with IBD in remission4 weeks

Many people with Crohn's or ulcerative colitis in remission still get gut symptoms. 52% on the low FODMAP diet reported adequate relief, compared with 16% on a sham diet. Inflammation markers didn't change, and Bifidobacteria fell as expected.

Takeaway: it may help ongoing symptoms, but it doesn't treat the inflammation. Only try it with your IBD team's guidance.

The bottom line

  • Low FODMAP is the best-studied diet for IBS. Around 50–80% of people improve, particularly with bloating and pain.
  • It's a three-step process: swap to low FODMAP for 2–6 weeks, reintroduce each group to find your triggers, then eat as widely as you can.
  • Rule out coeliac disease and other conditions first, and get a dietitian if you can. Results are better with one.
  • It's not a weight loss diet or a general "healthy" diet. If you don't have gut symptoms, there's no reason to cut FODMAPs.

References

  1. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 2014;146:67–75.
  2. van Lanen AS, de Bree A, Greyling A. Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis. Eur J Nutr 2021;60:3505–22.
  3. Cuffe MS et al. Efficacy of dietary interventions in irritable bowel syndrome: a systematic review and network meta-analysis. Lancet Gastroenterol Hepatol 2025.
  4. Rej A et al. Efficacy and acceptability of dietary therapies in non-constipated irritable bowel syndrome: a randomized trial of traditional dietary advice, the low FODMAP diet, and the gluten-free diet. Clin Gastroenterol Hepatol 2022;20:2876–87.
  5. Staudacher HM et al. Long-term personalized low FODMAP diet improves symptoms and maintains luminal Bifidobacteria abundance in irritable bowel syndrome. Neurogastroenterol Motil 2022;34:e14241.
  6. Wilson B, Cox SR, Whelan K. Challenges of the low FODMAP diet for managing irritable bowel syndrome and approaches to their minimisation and mitigation. Proc Nutr Soc 2021;80:19–28.
  7. Cox SR et al. Effects of low FODMAP diet on symptoms, fecal microbiome, and markers of inflammation in patients with quiescent inflammatory bowel disease in a randomized trial. Gastroenterology 2020;158:176–88.
  8. Vasant DH et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut 2021;70:1214–40.
  9. Lacy BE et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol 2021;116:17–44.
  10. Coeliac Australia. Testing for coeliac disease (health professional information).

Frequently Asked Questions

The strict stage (Step 1) should last only 2–6 weeks. If your symptoms have improved, move on to reintroduction. If nothing has changed after 4–6 weeks of following it carefully, it probably isn't the answer for you: go back to your normal diet and talk to your GP or dietitian about other options.

No. Low FODMAP limits wheat, rye and barley because of their fructans (a carbohydrate), not their gluten (a protein). A little wheat, like soy sauce or a slice of spelt sourdough, is fine on low FODMAP, but not for coeliac disease. And many gluten-free products contain high FODMAP ingredients such as inulin, honey or apple.

The FODMAPs in garlic and onion (fructans) dissolve in water, not in oil. So when garlic is gently cooked in oil and the pieces are removed, the flavour stays in the oil but the fructans don't. Shop-bought is safest. If you make your own, keep it in the fridge and use it within 2–3 days to avoid the risk of botulism.

Many people do, and this guide is designed to help. But trials show better results and fewer nutrition problems with a dietitian, especially for the reintroduction step. A dietitian is strongly recommended if you have a history of disordered eating, are pregnant, are underweight, or have other medical conditions.

It isn't designed for weight loss, and it isn't a healthier way to eat if you don't have gut symptoms. FODMAPs are actually good for your gut bacteria. If weight is your goal, see our Mediterranean or Fat Loss guides.

Stop the test, go back to low FODMAP until you feel settled, then move on to the next group. A reaction usually means you're sensitive to larger amounts, not all amounts. Many people can still eat a small serve of their trigger foods. You can retest it in a few months, as tolerance often improves.

iPhone: open this page in Safari, tap Share, then "Add to Home Screen". Android: open it in Chrome, tap ⋮, then "Add to Home screen". It gets its own icon, and your checklist, reintroduction results and shopping list are remembered on that phone.

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Disclaimer: This guide is general information based on published research. It is not medical advice and doesn't replace advice from your GP, gastroenterologist or an Accredited Practising Dietitian. See a doctor before starting, particularly if you have any of the warning signs listed. FODMAP ratings are simplified summaries and may change as foods are retested; nutrition values are estimates. Everyday Calculators is not affiliated with Monash University or FODMAP Friendly. "Monash University Low FODMAP Diet" and "FODMAP Friendly" are trademarks of their respective owners.