If you have irritable bowel syndrome (IBS), sooner or later someone will tell you to try a low-FODMAP diet. It is the most studied diet for IBS, and it shows up in gut-health advice for bloating, gluten sensitivity and lactose intolerance too. It is also widely misunderstood: it is not a gluten-free diet, not a weight-loss plan, and not meant to be followed strictly forever.
The short version
- FODMAPs are carbohydrates that some guts handle poorly: fructans (wheat, onion, garlic), galacto-oligosaccharides (beans), lactose, excess fructose (apples, honey) and polyols (sorbitol, mannitol).
- It is a three-step plan, not a lifelong diet: cut high-FODMAP foods for about 2 to 6 weeks, reintroduce them group by group to find your triggers, then eat as widely as you comfortably can.
- It has the most trial evidence of any IBS diet, but certainty is low: comparison diets often did nearly as well, and British guidelines say the 50 to 70 percent response rates may be overestimated.
- Do it with a dietitian if you can. Almost all trials of the diet used one, and in a real-world study people without one were less likely to follow reintroduction properly.
- Get checked first. Test for celiac disease while still eating wheat, and see a doctor for weight loss, anemia or blood in the stool. People with a history of eating disorders should not start it alone.
- Supplements are add-ons, not shortcuts. Psyllium and peppermint oil have IBS evidence; enzymes help some people with specific foods; inulin, chicory root and the sugar alcohols in many gummies are FODMAPs.
What FODMAPs are
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. In plain terms, they are short-chain carbohydrates that are either poorly absorbed in the small intestine or quickly fermented by gut bacteria. The diet tracks five groups:
- Fructans (an oligosaccharide, meaning a short chain of sugars): wheat, rye, onion, garlic, and added inulin, chicory root and fructo-oligosaccharides (FOS).
- Galacto-oligosaccharides (GOS): beans, lentils and other legumes.
- Lactose (a disaccharide, or double sugar): cow's milk, yogurt, custard and ice cream. See our lactose intolerance guide.
- Excess fructose (a monosaccharide, or single sugar): apples, pears, mango, honey and high-fructose corn syrup.
- Polyols (sugar alcohols): sorbitol and mannitol in some fruits, mushrooms and sugar-free products.
These carbohydrates draw water into the small intestine and produce gas when bacteria ferment them in the colon. Everyone's gut does this. What differs in IBS is sensitivity: in an MRI study comparing 29 people with IBS and 29 without, both groups produced similar amounts of water and gas, but the IBS group felt it more. The researchers concluded that symptoms come from a gut that is more sensitive to stretching, not from making extra gas.
The approach was developed at Monash University in Australia by Peter Gibson and Sue Shepherd, and the Monash team still runs the main food-testing program and app.
Who the low-FODMAP diet is for
The evidence base is IBS: recurring abdominal pain linked to bowel movements or changes in stool, at least weekly for three months. British guidelines treat it as a second step: they recommend first-line advice (regular meals, adjusting fiber, cutting back on alcohol, caffeine, fatty and spicy food), and then a low-FODMAP diet supervised by a trained dietitian if symptoms continue. The American Gastroenterological Association, by contrast, counts diet changes such as a low-FODMAP diet among the primary treatments for IBS symptoms.
- Bloating without IBS: a 2025 European consensus gave it a weak recommendation for functional bloating and distension, while noting that studies in people with bloating but no IBS are lacking. See our bloating guide.
- IBD in remission with IBS-type symptoms: in a 52-person trial, more people reported adequate relief (52 versus 16 percent), but inflammation did not change. It is a symptom tool, not an IBD treatment, and belongs with your IBD team.
- Self-reported gluten sensitivity: fructans, not gluten, may be the trigger for many; see our gluten sensitivity guide.
- SIBO: guidance treats the diet as supportive for symptoms; we found no trial showing it clears bacterial overgrowth. See supplements for SIBO.
Get checked first. IBS-type symptoms can come from celiac disease, which was more common in people with IBS in a review of 36 studies (though not in the few North American studies), and British and American guidelines advise celiac blood testing for many people with IBS. Because a low-FODMAP diet cuts wheat, test while you still eat it.
How to do the low-FODMAP diet: the three phases
| Phase | What you do | How long |
|---|---|---|
| 1. Restriction | Swap high-FODMAP foods for low-FODMAP ones across all five groups | About 2 to 6 weeks |
| 2. Reintroduction | Pick a food rich in only one FODMAP group (for example, cow's milk for lactose), eat it daily for 3 days while otherwise staying on the phase 1 diet, note symptoms, then move to the next group | Several weeks |
| 3. Personalization | Eat freely except your proven triggers, and only limit them as much as needed; retest over time | Long term |
Sources differ slightly on phase 1: Monash says 2 to 6 weeks, the American College of Gastroenterology says responders can be identified in 2 to 6 weeks, the American Gastroenterological Association says no more than 4 to 6 weeks, and British guidelines say 4 to 6 weeks.
How to start. Plan swaps for all five groups using the food table below and the Monash app's traffic-light ratings, and keep a simple symptom diary from day one. The diary tells you whether phase 1 helped and records your phase 2 tests. Foods that fail a test can be retried later, since tolerance can change.
If nothing improves after phase 1, stop. The American Gastroenterological Association says a diet that does not help within a set time should be abandoned for another treatment, and Monash advises considering other therapies. Not everyone with IBS responds, and staying restrictive without benefit only adds downsides.
Phase 3 is the goal. Strict, long-term restriction is not recommended because it narrows your diet and changes your gut bacteria. In a study that followed 103 people after dietitian-led teaching, with no comparison group, 57 percent had satisfactory relief long term, after reintroduction, and most (82 percent) were eating an adapted diet that still limited some FODMAPs.
A dietitian makes a difference. Almost all trials of the diet were dietitian-led. In a real-world study of 80 people, those who saw a dietitian were far more likely to follow reintroduction (70 versus 39 percent) and personalization (65 versus 29 percent) correctly. Group classes worked about as well as one-to-one sessions in one nonrandomized study. If you cannot see a dietitian, use well-made teaching materials and do not skip phase 2. Some dietitians start with a gentler version, sometimes called "FODMAP-gentle," that cuts only a few foods very high in FODMAPs; it is common in practice but less studied.
Low-FODMAP food list: what to limit and what to eat
These examples come from Monash University's published list. Portion size changes the rating for many foods, so a small serving of a "high" food may be fine; the Monash app gives tested serving sizes.
| Food group | Higher in FODMAPs | Lower in FODMAPs |
|---|---|---|
| Vegetables | Onion, garlic, leek, asparagus, artichoke, mushrooms, green peas | Carrot, cucumber, lettuce, potato, eggplant, green beans, bok choy |
| Fruit | Apples, pears, mango, cherries, watermelon, peaches, dried fruit | Orange, mandarin, kiwifruit, pineapple, blueberries, cantaloupe |
| Dairy | Cow's milk, yogurt, ice cream, custard | Lactose-free milk, hard cheeses, feta, brie, almond milk |
| Protein | Most beans and lentils, some processed meats | Eggs, firm tofu, tempeh, plain meat, poultry and seafood |
| Grains | Wheat, rye and barley breads, cereals and crackers | Oats, quinoa flakes, plain rice cakes, corn, quinoa or rice pasta, spelt sourdough bread |
| Nuts and seeds | Cashews, pistachios | Macadamias, peanuts, walnuts, pumpkin seeds |
| Sweeteners | Honey, high-fructose corn syrup, sugar-free sweets | Table sugar, maple syrup, rice malt syrup, dark chocolate |
On labels, look for hidden FODMAPs: inulin, chicory root, FOS, oligofructose, honey, high-fructose corn syrup, garlic and onion powder, and sweeteners ending in "-itol" such as sorbitol, mannitol, xylitol and maltitol.
Does the low-FODMAP diet work? What the trials show
The low-FODMAP diet has more trials than any other IBS diet, but the picture is more modest than its reputation.
- A carefully controlled feeding trial. In a 2014 Monash trial of 30 people with IBS, with almost all food provided, overall symptom scores were 22.8 on the low-FODMAP diet versus 44.9 on a typical Australian diet, on a 0 to 100 mm scale where lower is better.
- A sham-diet trial. In a 104-person trial that compared the diet with a convincing sham diet, adequate relief was 57 versus 38 percent, a difference that just missed statistical significance, though symptom scores improved.
- Against standard advice. Several trials found traditional IBS diet advice did nearly as well: 50 versus 46 percent in Sweden, and 55 percent on low-FODMAP, 58 percent on gluten-free and 42 percent on traditional advice in a 2022 UK trial, with no significant differences.
- Pooled analyses. A 2022 analysis of 13 randomized trials ranked low-FODMAP first among IBS diets, and a 2025 analysis of 28 trials found the most evidence for it but ranked it fourth for overall symptoms, with most comparisons rated low or very low certainty (how confident reviewers are that a result is real). A diet cutting starch and sucrose (table sugar) ranked first in that 2025 analysis, based on only two trials, and matched low-FODMAP in a 2024 head-to-head trial.
British guidelines call the low-FODMAP diet an effective second-line treatment for overall IBS symptoms and pain, but rate the recommendation weak and the evidence very low quality, and say the 50 to 70 percent benefit often quoted "may have been overestimated." The American College of Gastroenterology recommends a limited trial of the diet. The fair summary: in trials, roughly half to three-quarters of people on the diet met response targets, but simpler advice often helped nearly as many, and most trials tested only the restriction phase.
Downsides to know about
- Gut bacteria change. The restriction phase lowers bifidobacteria, beneficial gut bacteria, in most trials that measured them. The long-term meaning is unknown, which is one reason not to stay strict.
- Diet quality can drop. In an analysis of 130 people from two trials, the diet did not affect most nutrients but lowered overall diet quality, and fiber fell in another trial. Calcium and fiber are the main watch-points, since dairy and wheat are cut.
- It can feed disordered eating. In one IBS program, 23 percent of patients were at risk of eating-disorder behavior. Restrictive diets are a poor fit for anyone with an eating disorder, avoidant/restrictive food intake disorder (ARFID, eating a very narrow range of foods, for example out of fear of symptoms), malnutrition or food insecurity.
- It is effortful. People report extra cost, harder social eating and a real burden of planning.
Low-FODMAP supplements: what helps and what to avoid
No supplement treats IBS, and none replaces the reintroduction phase. Some can help alongside the diet; our IBS supplement guide covers the wider evidence.
Psyllium (soluble fiber). British and American guidelines support soluble fiber such as ispaghula (psyllium) for overall IBS symptoms, and British guidelines advise starting low (3 to 4 g a day) and building up slowly. In a primary-care trial of 275 people, 57 percent improved in the first month on 10 g of psyllium a day versus 35 percent on placebo. Insoluble wheat bran is not recommended. See our psyllium page and fiber supplement ranking.
Watch for high-FODMAP fiber. Inulin, chicory root and FOS are fructans. In the MRI study above, 13 of 29 people with IBS reached the symptom threshold after inulin, versus 6 after glucose. They are common in gut gummies, protein bars and greens powders.
Enzymes for specific triggers. Monash researchers describe enzymes as an add-on for people who already know their triggers, not a panacea.
- Lactase (lactose): helps many people with lactose intolerance; see our lactose guide.
- Alpha-galactosidase (GOS in beans): eased symptoms in a small trial of people with IBS sensitive to GOS, but showed only a trend in a 125-person, 12-week IBS trial and no benefit in another small trial.
- Fructan-digesting enzymes: break down fructans in lab studies. In a 2026 study of 30 healthy adults funded by an enzyme supplier, the main symptom measure was not met after a high-inulin meal, though pain and fatigue were lower in the first 8 hours and several symptoms were lower from 8 to 24 hours. We found no trial in people with IBS.
- Xylose isomerase (excess fructose): reduced breath hydrogen and some symptoms after a single fructose drink in 65 people with fructose malabsorption; we found no IBS trial.
Peppermint oil. A 2022 meta-analysis of 10 trials in 1,030 adults favored peppermint oil over placebo for IBS symptoms, at very low certainty, and heartburn is a common side effect. See peppermint oil for IBS.
Probiotics. In the sham-diet trial, a probiotic restored bifidobacteria but did not add symptom relief. British guidelines say probiotics as a group may help IBS but cannot recommend a specific strain; see probiotic strains for IBS.
Sugar alcohols in supplements. Chewables, gummies and "sugar-free" products often contain sorbitol, mannitol, xylitol or maltitol. In one study, 10 g of sorbitol or mannitol increased symptoms in people with IBS. Erythritol was better tolerated than xylitol in healthy volunteers, but its place on a low-FODMAP diet is not settled.
"Low FODMAP certified" labels. Monash and FODMAP Friendly test products and certify those that meet low-FODMAP cutoffs. Certification means the product met that program's low-FODMAP cutoffs in testing, not that it treats IBS or works for its other claims.
Who should be careful
- Rule out other causes. See a doctor for weight loss, anemia, blood in the stool or black stools, or a family history of celiac disease, inflammatory bowel disease or bowel cancer. Test for celiac disease while still eating wheat. If wine, aged cheese or fermented foods seem to be your triggers, our guide to histamine intolerance explains how histamine reactions and FODMAP reactions overlap.
- Eating disorders. If you have, or have had, an eating disorder or ARFID, or are underweight, do not start a restrictive diet without your care team.
- Children and pregnancy. Children should do it only with their clinician and a pediatric dietitian. We found no trials of the diet in pregnancy; talk with your clinician.
- Do not stay strict. Move on to reintroduction after 2 to 6 weeks, and stop if nothing improves.
Frequently asked questions
What is a low-FODMAP diet, and what does FODMAP stand for?
A short-term eating plan, used mainly for IBS, that cuts foods high in FODMAPs and then adds them back to find your personal triggers. FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols: short-chain carbohydrates that are poorly absorbed or quickly fermented. The diet tracks five groups: fructans, galacto-oligosaccharides, lactose, excess fructose and polyols such as sorbitol and mannitol.
How long should you stay on the low-FODMAP diet?
The strict restriction phase lasts about 2 to 6 weeks (Monash says 2 to 6 weeks; British guidelines say 4 to 6). It is followed by reintroduction, testing one FODMAP group at a time, and then a personalized long-term diet that limits only your proven triggers. If nothing improves after the restriction phase, the American Gastroenterological Association and Monash advise stopping and considering other treatments.
Does the low-FODMAP diet work for IBS?
For many people, yes, but the evidence is of low certainty. It has the most trials of any IBS diet and roughly half to three-quarters of people counted as responders in trials (their symptoms improved by a preset amount), but traditional IBS diet advice often did nearly as well, and British guidelines say the commonly quoted 50 to 70 percent benefit may be overestimated.
Is the low-FODMAP diet the same as gluten-free?
No. The low-FODMAP diet cuts wheat because of its fructans, not its gluten, and it also limits onion, garlic, beans, some fruits, lactose and sugar alcohols. Small amounts of wheat may be fine after reintroduction. If celiac disease is possible, get tested before cutting wheat.
Do you need a dietitian for the low-FODMAP diet?
It is strongly advised. Almost all trials of the diet were dietitian-led, and in a real-world study people who saw a dietitian were far more likely to follow the reintroduction and personalization phases correctly. Good teaching materials can help if a dietitian is not available.
Are there supplements that help on a low-FODMAP diet?
Some, as add-ons. Psyllium and peppermint oil have IBS evidence. Lactase helps many people with lactose intolerance, and alpha-galactosidase helps some people sensitive to beans with specific meals. Fructan enzymes are promising in lab studies but untested in IBS. Avoid inulin, chicory root, FOS and sugar alcohols such as sorbitol and mannitol during restriction.
Is it safe to stay on the low-FODMAP diet long term?
Strict restriction is not meant to be long term. It lowers beneficial bifidobacteria and can reduce diet quality and fiber, and it is a poor fit for people with eating disorders. The goal is a personalized diet that limits only your triggers; in one follow-up study, 57 percent of people still reported satisfactory relief after reintroduction.
What foods can you eat on a low-FODMAP diet?
Plenty. Lower-FODMAP choices on Monash University's list include eggs, plain meat, poultry and seafood, firm tofu, oats, quinoa flakes, plain rice cakes, potato, carrot, cucumber, eggplant, oranges, kiwifruit, pineapple, lactose-free milk, hard cheeses, walnuts and maple syrup. Portion size changes the rating for many foods, so check serving sizes in the Monash app.
How do you reintroduce FODMAPs?
After 2 to 6 weeks of restriction, test one FODMAP group at a time: eat a food rich in only that group daily for 3 days while otherwise staying on the restricted diet, note symptoms, then move to the next group. A dietitian can help choose the test foods and order. Foods that cause symptoms can be retried later.
Is the low-FODMAP diet good for bloating?
It can help. In a 2025 analysis of IBS diet trials it was the only diet that beat usual eating for bloating, and a 2025 European consensus gave it a weak recommendation for bloating without IBS, while noting that studies in people who have bloating but not IBS are lacking. Get red-flag symptoms checked first, and treat it as a short test, not a permanent diet.
The bottom line
The low-FODMAP diet is the best-studied diet for IBS, and it helps many people, mainly by reducing bloating and pain. But the evidence is of low certainty, simpler diet advice works nearly as well for some, and the diet is meant to be a short test, followed by reintroduction and a personal long-term diet, not a permanent restriction.
Get checked for celiac disease and red-flag symptoms first, use a dietitian if you can, and keep the restriction phase short. Psyllium and peppermint oil have IBS evidence worth discussing, enzymes help some people with known triggers, and inulin, chicory root and sugar alcohols in supplements are common hidden FODMAPs.