Dr. Elizabeth Squirell

The low-FODMAP diet

A short-term, 3-step eating plan that helps many people with IBS find which foods trigger gas, bloating, pain and diarrhea. Best done with a dietitian.

Reviewed October 2026 6 min read

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At a glance

  • The low-FODMAP diet is for irritable bowel syndrome (IBS), or IBS-type symptoms when IBD is calm. Get a diagnosis from your doctor first.
  • It has 3 steps: cut back on high-FODMAP foods for 2 to 6 weeks, test them back one group at a time, then eat as widely as you can.
  • It is not a forever diet. Step 1 is short. The goal is to eat as many foods as you comfortably can.
  • Work with a registered dietitian who knows the diet, so you stay well fed.
  • Use the Monash University FODMAP Diet app (it has a small one-time fee) to check foods and serving sizes.
  • In Ontario, you can call 811 (Health811) to talk with a registered dietitian for free.
  • If Step 1 does not help after 6 weeks, stop and talk to your doctor or dietitian.
  • Not for weight loss, and not a good choice if you have or had an eating disorder, or you are underweight.

FODMAPs are types of carbohydrate found in many everyday foods. For most people they cause no trouble. In people with irritable bowel syndrome (IBS), they can cause gas, bloating, belly pain, diarrhea or constipation. A low-FODMAP diet helps you find which ones bother you, so you can avoid only those.

What are FODMAPs?

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. These are sugars and fibres that the small bowel doesn’t absorb well. They move on to the large bowel. There they pull in water, and gut bacteria feed on them and make gas.

In people with IBS, the gut is more sensitive. The extra water and gas can cause pain and changes in bowel habits.

The main groups are:

The 5 main FODMAP groups
Group Found in, for example
Lactose Cow’s milk, yogurt, soft cheeses
Fructose (extra) Apples, pears, mango, honey
Fructans Wheat, rye, onion, garlic
GOS (galacto-oligosaccharides) Beans, lentils, chickpeas
Polyols Apples, pears, mushrooms, sugar-free gum and mints

FODMAPs are not “bad.” Many high-FODMAP foods are very healthy. The goal is to find your own triggers, not to avoid them all.

Who is it for?

  • People with IBS. Your doctor should confirm the diagnosis first. Other problems, like celiac disease, should be ruled out.
  • People with IBD in remission who still have IBS-type symptoms. First, your IBD team should check that your IBD is not active, for example with a stool or blood test. In one study of people with calm IBD, about half felt better on the diet, compared with about 1 in 6 on a sham diet. A sham diet looks like a special diet: you cut out some foods, but it is not low in FODMAPs. This lets researchers compare the two fairly. The low-FODMAP diet did not change inflammation. European and international IBD experts now advise a short trial of the diet for this (2025 and 2026). It eases symptoms, but it does not treat IBD or keep it calm.

Canadian and American experts suggest trying the diet for IBS. In one well-done trial, more people felt better on the diet than on a sham diet. Symptom scores were also clearly lower on the low-FODMAP diet. It does not help everyone.

How many people felt better after 4 weeks

People with IBS (104 people)

  • Low-FODMAP diet57 in 100
  • Sham diet38 in 100

People with calm IBD (52 people)

  • Low-FODMAP diet52 in 100
  • Sham diet16 in 100

Two studies. Each compared the low-FODMAP diet with a sham diet (one that cuts out some foods but is not low in FODMAPs), for 4 weeks. In the IBS study, the gap was just short of clear proof.

The 3 steps

  1. 2 to 6 weeks

    Step 1: Swap

    Replace high-FODMAP foods with lower-FODMAP choices. If your symptoms don’t improve after 6 weeks, stop. The diet may not be right for you.

  2. Several weeks

    Step 2: Test

    Stay on your Step 1 diet, and bring back one FODMAP group at a time. Eat a test food each day for 3 days, and watch for symptoms. When you feel settled, test the next group.

  3. Long term

    Step 3: Personalise

    Eat as widely as you can. Limit only the foods or amounts that clearly bother you.

Serving size matters. Some foods are fine in a small amount but cause symptoms in a large one. The Monash University FODMAP Diet app lists foods and serving sizes. It is made by the team that created the diet. The app has a small one-time fee.

Simple swaps

These examples are from Monash University’s testing. Check the app for serving sizes.

  • Instead of Regular wheat bread, try Sourdough spelt bread, or gluten-free bread without onion, honey or pear
  • Instead of Cow's milk, try Lactose-free milk
  • Instead of Onion and garlic, try The green part of green onions, chives, or garlic-infused oil
  • Instead of Apple, pear, mango, watermelon, try Orange, kiwi, firm (less ripe) banana, blueberries
  • Instead of Cauliflower, mushrooms, try Carrots, eggplant, green bell pepper
  • Instead of Honey, try Pure maple syrup
  • Instead of Kidney beans, baked beans, try Canned chickpeas or lentils, rinsed, in a small serving (for example, ¼ cup chickpeas)
  • Instead of Cashews, pistachios, try Peanuts, walnuts, macadamia nuts
  • Instead of Ricotta or cottage cheese, try Hard cheese like cheddar or parmesan, or brie, camembert or feta
  • Instead of Sugar-free gum and mints (sorbitol, mannitol, xylitol), try Regular gum or mints

Garlic-infused oil works because FODMAPs don’t dissolve in oil. Just don’t eat the garlic pieces.

Cautions

  • It is not a forever diet. Staying on Step 1 for a long time can lower your fibre, iron and calcium. It also lowers some helpful gut bacteria.
  • It is not a weight-loss diet. The limits aren’t needed for weight loss.
  • It is not a gluten-free diet. It limits wheat because of fructans, not gluten. Only people with celiac disease need a strict gluten-free diet.
  • It is not a good fit for everyone. Talk to your doctor first if you have, or have had, an eating disorder. The same goes if you are underweight, losing weight without trying, or have trouble affording food.
  • Children. There is little research in children. Children should only try this with their doctor and a dietitian who works with children.

Other things that help IBS

Food is only one part of IBS care. Other options with good evidence include:

  • Soluble fibre such as psyllium, added slowly
  • Peppermint oil capsules
  • Gut-directed therapies, like cognitive behavioural therapy (CBT) or gut-directed hypnotherapy
  • Medicines that your doctor may suggest, depending on your symptoms
Can I do this diet on my own?

Many people try, but it’s harder to do well. It’s easy to cut out too much, or to skip the testing step. A dietitian makes it safer and more useful. In Ontario, you can call 811 (Health811) to talk with a registered dietitian for free. If you can’t see a dietitian in person right away, use the Monash app and keep Step 1 short.

My symptoms didn't change at all. What now?

Stop the diet and go back to your usual foods. FODMAPs may not be your main trigger. Talk to your doctor about other options.

Read next

Sources for this guide

Sources

  1. Moayyedi P, et al. Canadian Association of Gastroenterology clinical practice guideline for the management of irritable bowel syndrome. J Can Assoc Gastroenterol 2019;2:6–29. PMID 31294724 Statement 10: suggest a low-FODMAP diet for IBS (conditional, very low-quality evidence); with a dietitian, strict phase as short as possible (e.g., 4 weeks); long-term use not recommended; can lower Bifidobacteria; suggests against a gluten-free diet; recommends psyllium
  2. Lacy BE, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol 2021;116:17–44. PMID 33315591 Recommends a limited trial of a low-FODMAP diet to improve global IBS symptoms
  3. Chey WD, et al. AGA clinical practice update on the role of diet in irritable bowel syndrome. Gastroenterology 2022;162:1737–45. PMID 35337654 Three phases: restriction (no more than 4–6 weeks), reintroduction, personalization; dietitian referral; poor candidates include people at risk of malnutrition, food insecurity, or with an eating disorder; stop a diet that doesn't help
  4. Monash University. Starting the low FODMAP diet. Step 1 for 2–6 weeks; Step 2 challenges one FODMAP group daily for 3 days; Step 3 relax restrictions as much as possible; follow with a dietitian skilled in IBS
  5. Monash University. High and low FODMAP foods. Source for the higher- and lower-FODMAP examples in the swap table
  6. Monash University. Getting enough fibre on a low FODMAP diet (Varney J, 2021). Low-FODMAP serving sizes: orange 1 medium, kiwi 2 small, firm banana 1 medium, carrot, eggplant, canned chickpeas ¼ cup (42 g), peanuts, walnuts, macadamias
  7. Monash University. Frequently asked questions. FODMAPs are not soluble in oil (garlic-infused oil); ricotta has moderate lactose; hard cheeses low; not a gluten-free diet; rinse canned legumes
  8. Varney J. The FODMAP diet is everywhere, but researchers warn it's not for weight loss. Monash University / The Conversation, February 2020. Not designed for weight loss; can compromise fibre, iron and calcium intake if not carefully done
  9. Staudacher HM, et al. A diet low in FODMAPs reduces symptoms in patients with irritable bowel syndrome and a probiotic restores Bifidobacterium species: a randomized controlled trial. Gastroenterology 2017;153:936–47. PMID 28625832 104 people with IBS, 4 weeks: adequate relief 57% low FODMAP vs 38% sham diet (intention to treat, P=0.051, not significant); IBS-SSS lower on the diet (173 vs 224, P=0.001); Bifidobacterium lower on the diet
  10. Cox SR, et al. Effects of low FODMAP diet on symptoms, fecal microbiome, and markers of inflammation in patients with quiescent inflammatory bowel disease. Gastroenterology 2020;158:176–88. PMID 31586453 52 people with IBD in remission and ongoing gut symptoms, 4 weeks: adequate relief 52% low FODMAP vs 16% control diet (P=0.007); single-blind, the control was a sham diet with dietary advice (described as a sham exclusion diet of similar intensity by Grammatikopoulou MG et al., Nutrients 2020;12:3648, PMID 33260902); no change in inflammation markers
  11. Colombel JF, et al. AGA clinical practice update on functional gastrointestinal symptoms in patients with IBD. Clin Gastroenterol Hepatol 2019;17:380–90. PMID 30099108 Rule out active inflammation first; a low-FODMAP diet may be offered for functional symptoms in IBD with attention to nutrition
  12. Iacovou M. Evidence for the use of the low FODMAP diet in children. Monash University blog, 2015. Little research in children; IBS should be properly diagnosed by a doctor
  13. Svolos V, et al. European Crohn's and Colitis Organisation consensus on dietary management of inflammatory bowel disease. J Crohns Colitis 2025;19(9):jjaf122. PMID 40650933 Statement 20.1: in adults with quiescent IBD and IBS-like symptoms, a low-FODMAP diet is recommended (EL1, 100% consensus). Statement 12: not recommended for maintaining remission in Crohn's disease
  14. Ma C, et al. Recommendations for the evaluation and management of inflammatory bowel disease with IBS-like symptoms: a joint Rome Foundation and IOIBD consensus. Gastroenterology 2026;171:504–20. PMID 42066865 Diagnose IBS-like symptoms in IBD only after objectively excluding inflammation; appropriate therapies include psyllium (if no stricture), a short-term low-FODMAP diet, targeted drugs and brain-gut behavioural therapies
  15. Government of Ontario. Healthy choices (updated June 2026). Visit Health811 online or call 811 and speak to a registered dietitian about nutrition and healthy eating
  16. Monash University. Monash FODMAP Diet app (App Store / Google Play listings, checked October 2026). The app is made by the Monash research team, uses a traffic-light food guide and is a paid app with a one-time fee (about US$8–10 in app-store listings; Canadian price not confirmed)

This guide is for general education. It can't replace advice from your own care team, who know your health history.

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