FODMAP Diets……What?

Last week, we discussed inflammatory foods and diets, and I mentioned the FODMAP diet briefly in the blog. In the days since, I’ve received multiple questions: What is a FODMAP diet? What is it used for? So, this week, I am going to talk about FODMAP diets. Let’s dive in.

It's an Acronym

FODMAP is actually an acronym. It stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. That is a mouth full of big words. These are each short-chain carbohydrates, aka sugars, found in many common foods. They are poorly absorbed in the small intestine, and during digestion, they increase intestinal water content and are rapidly fermented by colonic bacteria. This can lead to gas production and triggers bloating, pain, and altered bowel habits especially in patients with irritable bowel syndrome.1-6

This should not be confused with proinflammatory foods. As we discussed last week, those are foods that cause inflammatory cytokines to increase after eating, and the biggest culprit are processed foods. FODMAP foods cause discomfort because their digestion leads to gas and increased water, not inflammation. It is very important to understand this and not incorrectly call these foods inflammatory. They do not cause systemic effects like inflammatory foods do; they cause localized GI irritation. That’s an important distinction.

What Foods are Involved?

Knowing the scientific terminology is great but what are the actual foods that make up FODMAP?

Oligosaccharides: These are made up by fructans and galacto-oligosaccharides (GOS). Fructans are found in wheat, rye, onions, garlic, leeks, asparagus, artichokes, and certain fruits like watermelon. GOS are present in legumes such as lentils, chickpeas, kidney beans, and soybeans.3,7-10

Disaccharides: The primary disaccharide of concern is lactose, found in milk, soft cheeses, yogurt, and other dairy products containing lactose.3,7,8

Monosaccharides: This category mainly refers to excess fructose relative to glucose. Foods high in excess fructose include apples, pears, mangoes, watermelon, honey, agave, and high-fructose corn syrup–containing processed foods.3,7-9

Polyols: These sugar alcohols include sorbitol and mannitol, found naturally in some fruits and vegetables such as apples, pears, cherries, peaches, plums, cauliflower, mushrooms, and snow peas. It also includes the artificial sweeteners like xylitol and maltitol used in sugar-free gums and candies.3,7-10

You may be wondering, “So what do people actually eat while on a low FODMAP diet?” Low FODMAP alternatives include gluten-free grains such as rice, oats, and quinoa; lactose free dairy or hard cheeses; most berries; citrus fruits; bananas; carrots; spinach; potatoes; and protein foods like eggs, fish and meat.3,7,11-14

How Does One Implement This Diet?

The main purpose of the diet is to identify individual sensitivities to these carbohydrate groups. The diet is typically implemented in three phases: (1) elimination of high-FODMAP foods for 2–8 weeks, (2) gradual reintroduction of individual FODMAP groups to identify specific triggers, and (3) personalization to maintain the least restrictive, nutritionally adequate diet.2,11-13

There is no specific order in which foods or FODMAP categories must be reintroduced during the reintroduction phase of the low FODMAP diet. The American Gastroenterological Association states that the reintroduction phase involves challenging patients with foods containing a single FODMAP, consumed in increasing quantities over several days, while monitoring symptoms. The order of reintroduction depends on patient preferences, dietary habits, and clinical judgment, not a fixed sequence.11 However, fructans and mannitols are the most common triggers during reintroduction testing.10

Is There Evidence to Support It?

Yes. There are several systematic reviews and meta-analyses demonstrating a low FODMAP diet improves GI symptoms and IBS. One study of 944 patients found that a low FODMAP diet improved IBS symptoms, abdominal pain, and bloating compared to other dietary interventions.15 Another study found similar findings.16 The American College of Gastroenterology guideline state 1 out of every 5 IBS patients will experience improvement of symptoms.2,12 Additional systematic reviews confirm these findings, with consistent improvements in abdominal pain, bloating, stool frequency, and stool consistency across IBS subtypes.17-21

However, the FODMAP diet is not without issue. First, it is important to note that most trials are of short duration, have high risk of bias, and often lack assessment of FODMAP reintroduction or long-term safety. Second, it’s a very restrictive diet and can cause deficiencies in fiber, calcium, iron, zinc, folate, B and D vitamins along with several natural antioxidants.4 The American Gastroenterological Association and the American College of Gastroenterology recommend that the diet be implemented with dietitian supervision due to its restrictive nature and potential nutritional risks.2,11,12

Lastly, this is not meant to be a permanent diet. The purpose is to find which short-chain carbohydrates and how much of them trigger symptoms. Lifelong low-FODMAP diets are rare and should only be followed under a dietician’s care.

Next Steps

The FODMAP diet is extremely restrictive. Its purpose is to identify individually problematic food categories. It should never be done without professional guidance. It’s also important to note that IBS has functional components. Stress, sleep and other lifestyle factors contribute to symptoms. Using a FODMAP diet without addressing those factors is an incomplete treatment plan.

Personally, I have IBS. My triggers are stress and poor sleep, so I use exercise as my main treatment. I work out the stress, think more clearly so I can find solutions, and I’m usually so tired afterwards that it helps me sleep. I also couldn’t fathom cutting out so many delicious, healthy foods, so no FODMAP for me. You should talk to your doctor about what options may work for you.

Disclaimer: Even though I’m a doctor, I’m not your doctor—and reading this blog does not establish a doctor–patient relationship. This information is intended for general educational purposes only and should not be taken as personalized medical advice. Always speak with your own healthcare provider before making decisions about your health.

References

  1. Ford AC, Lacy BE, Talley NJ. Irritable Bowel Syndrome. The New England Journal of Medicine. 2017;376(26):2566-2578. doi:10.1056/NEJMra1607547
  2. Lacy BE, Pimentel M, Brenner DM, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. The American Journal of Gastroenterology. 2021;116(1):17-44. doi:10.14309/ajg.0000000000001036
  3. Shepherd SJ, Lomer MC, Gibson PR. Short-Chain Carbohydrates and Functional Gastrointestinal Disorders. The American Journal of Gastroenterology. 2013;108(5):707-717. doi:10.1038/ajg.2013.96
  4. Catassi G, Lionetti E, Gatti S, Catassi C. The Low FODMAP Diet: Many Question Marks for a Catchy Acronym. Nutrients. 2017;9(3):E292. doi:10.3390/nu9030292
  5. Quigley EMM. Gastrointestinal Effects of Diets Low in Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. Current Opinion in Clinical Nutrition and Metabolic Care. 2022;25(4):260-264. doi:10.1097/MCO.0000000000000841
  6. Vakil N. Dietary Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols (FODMAPs) and Gastrointestinal Disease. Nutrition in Clinical Practice : Official Publication of the American Society for Parenteral and Enteral Nutrition. 2018;33(4):468-475. doi:10.1002/ncp.10108
  7. Varney J, Barrett J, Scarlata K, et al. FODMAPs: Food Composition, Defining Cutoff Values and International Application. Journal of Gastroenterology and Hepatology. 2017;32 Suppl 1:53-61. doi:10.1111/jgh.13698
  8. Wang XJ, Camilleri M, Vanner S, Tuck C. Review Article: Biological Mechanisms for Symptom Causation by Individual FODMAP Subgroups – The Case for a More Personalised Approach to Dietary Restriction. Alimentary Pharmacology & Therapeutics. 2019;50(5):517-529. doi:10.1111/apt.15419
  9. Muir JG, Rose R, Rosella O, et al. Measurement of Short-Chain Carbohydrates in Common Australian Vegetables and Fruits by High-Performance Liquid Chromatography (HPLC). Journal of Agricultural and Food Chemistry. 2009;57(2):554-565. doi:10.1021/jf802700e
  10. Van den Houte K, Colomier E, Routhiaux K, et al. Efficacy and Findings of a Blinded Randomized Reintroduction Phase for the Low FODMAP Diet in Irritable Bowel Syndrome. Gastroenterology. 2024;167(2):333-342. doi:10.1053/j.gastro.2024.02.008
  11. Chey WD, Hashash JG, Manning L, Chang L. AGA Clinical Practice Update on the Role of Diet in Irritable Bowel Syndrome: Expert Review. Gastroenterology. 2022;162(6):1737-1745. doi:10.1053/j.gastro.2021.12.248
  12. Ford AC, Moayyedi P, Chey WD, et al. American College of Gastroenterology Monograph on Management of Irritable Bowel Syndrome. The American Journal of Gastroenterology. 2018;113(Suppl 2):1-18. doi:10.1038/s41395-018-0084-x
  13. Moshiree B, Drossman D, Shaukat A. AGA Clinical Practice Update on Evaluation and Management of Belching, Abdominal Bloating, and Distention: Expert Review. Gastroenterology. 2023;165(3):791-800. doi:10.1053/j.gastro.2023.04.039
  14. Lomer MCE. The Low FODMAP Diet in Clinical Practice: Where Are We and What Are the Long-Term Considerations? The Proceedings of the Nutrition Society. 2024;83(1):17-27. doi:10.1017/S0029665123003579
  15. Black CJ, Staudacher HM, Ford AC. Efficacy of a Low FODMAP Diet in Irritable Bowel Syndrome: Systematic Review and Network Meta-Analysis. Gut. 2022;71(6):1117-1126. doi:10.1136/gutjnl-2021-325214
  16. 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. European Journal of Nutrition. 2021;60(6):3505-3522. doi:10.1007/s00394-020-02473-0
  17. Varjú P, Farkas N, Hegyi P, et al. Low Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols (FODMAP) Diet Improves Symptoms in Adults Suffering From Irritable Bowel Syndrome (IBS) Compared to Standard IBS Diet: A Meta-Analysis of Clinical Studies. PloS One. 2017;12(8):e0182942. doi:10.1371/journal.pone.0182942
  18. Khalighi Sikaroudi M, Soltani S, Ghoreishy SM, et al. Effects of a Low FODMAP Diet on the Symptom Management of Patients With Irritable Bowel Syndrome: A Systematic Umbrella Review With the Meta-Analysis of Clinical Trials. Food & Function. 2024;15(10):5195-5208. doi:10.1039/d3fo03717g
  19. Hahn J, Choi J, Chang MJ. Effect of Low FODMAPs Diet on Irritable Bowel Syndromes: A Systematic Review and Meta-Analysis of Clinical Trials. Nutrients. 2021;13(7):2460. doi:10.3390/nu13072460
  20. Kuźmin L, Kubiak K, Lange E. Efficacy of a Low-Fodmap Diet on the Severity of Gastrointestinal Symptoms and Quality of Life in the Treatment of Gastrointestinal Disorders-a Systematic Review of Randomized Controlled Trials. Nutrients. 2025;17(12):2045. doi:10.3390/nu17122045
  21. Dionne J, Ford AC, Yuan Y, et al. A Systematic Review and Meta-Analysis Evaluating the Efficacy of a Gluten-Free Diet and a Low FODMAPs Diet in Treating Symptoms of Irritable Bowel Syndrome. The American Journal of Gastroenterology. 2018;113(9):1290-1300. doi:10.1038/s41395-018-0195-4

One comment on “FODMAP Diets……What?”

  1. Ronak Patel

    Nice blog! Simple yet impactful.

    Reply

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