Understanding And Implementing The Low Fodmap Diet

  • Rana IbrahimMasters of Critical care - Faculty of Medicine, Alexandria University, Egypt

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FODMAP is an acronym for fermentable oligo-, di- and monosaccharides [ mon-uh-sak-uh-rahyd, -er-id ], and polyols [ pol-ee-awl, -ol ].1 FODMAPs have a significant effect on the health of your digestive system that’s why the recent evidence-based guidelines recommend a low FODMAP diet to people who suffer from some digestive system illnesses such as irritable bowel syndrome (IBS), irritable bowel disease (IBD), diverticulitis and coeliac disease because FODMAP foods are not absorbed properly in your gut causing various symptoms. This article will guide you to understand more about the principles of a low FODMAP diet and its implementation.2

Understanding FODMAPs

In modern research, there have been findings that are related to abnormalities in the digestion of some food elements, such as lactose intolerance, where some individuals have a defective enzyme that is responsible for the breakdown of lactose. This causes symptoms such as abdominal pain, bloating or diarrhoea when they consume lactose-containing food, such as milk or cheese. Another example is individuals with coeliac disease are known to have difficulty digesting gluten-containing food.

Similarly, food containing other saccharides was reported to be the causative agent for some digestive manifestations. These saccharides are fermentable oligo-, di-, mono-saccharides, and polyols, given the acronym “FODMAP”. FODMAP foods are small non-digestable carbohydrates (sugar) containing few sugars which are poorly absorbed in the small bowel.3

You can find FODMAPs in some fruits, vegetables, legumes, cereals, honey, milk and dairy products, and some sweeteners. They are classified into food with low or high FODMAP.

(A full list can be downloadable here, or here)

High FODMAP food:

  • Dairy-based milk, yoghurt and ice cream
  • Products made from wheat such as bread, cereal and crackers
  • Beans and lentils
  • Certain veggies, such as garlic, onions, asparagus, and artichokes
  • Certain fruits, like pears, peaches, apples, and cherries

Low FODMAP food:

  • Eggs and meat
  • Some cheeses, including feta, cheddar, brie, and Camembert
  • Almond milk, oat milk
  • Grains like rice, quinoa and oats
  • Veggies such as tomatoes, cucumbers, potatoes, eggplant, and zucchini
  • Fruits including pineapple, oranges, grapes, strawberries, and blueberries

In a study, high and low FODMAP foods were introduced in different ratios to healthy and diseased individuals with IBS. It was concluded that symptoms greatly varied between these two groups, where they were severe in people with IBS.4 Such symptoms include abdominal pain, bloating, diarrhoea or constipation, and back pain.

The low FODMAP diet

Definition and mechanism

A low FODMAP diet means consuming food that is low in saccharides so that it would lead to less fermentation by our gut bacteria leading to less gas production and fewer symptoms. The underlying mechanism is that a low-FODMAP diet results in less water in the small intestine, less gas generation from bacteria, and less formation of short-chain fatty acids, which minimises intestinal distention. These can worsen visceral sensitivity and colonic contractions.5

Historical background

The efficacy of the diet, the mechanisms of action, and the food composition of FODMAPs have all been the subject of much research over the past 12 years. Nowadays, the low-FODMAP diet is regarded as the first line of treatment for IBS in many parts of the world. Having a clear structure and precise definition, it has become a well-known and widely-practised diet for many digestive conditions.6

Conditions treated with the low FODMAP diet

When first implemented, a low FODMAP diet was studied in individuals suffering from IBS. However, soon it was clear that IBD patients and patients with bacterial overgrowth can also benefit from such a regime. Therefore, if you are one of these patients you should consult your physician about starting this diet and giving it a try. Other conditions which also may benefit from such a diet are coeliac disease and diverticulitis, although there are far fewer studies on their outcome.

Irritable bowel syndrome and the low FODMAP diet

IBS is a chronic digestive disorder that is caused by many factors such as genetics, diet, intestinal bacteria (normal flora), low-grade inflammation, and abnormalities of the gastrointestinal cells. Among the common symptoms that these patients encounter are: intermittent lower abdominal pain, changed bowel habits(constipation/diarrhoea), and abdominal bloating/distension. Diagnosis is based on assessing the symptoms by Rome criteria where they are subdivided into many categories that are based on cause.7

For the treatment of at least some IBS patients, a low-FODMAP diet seems to work well.8 Patients with IBS most likely experience symptoms from FODMAPs because of the bowel distension and hypersensitivity. Accordingly, these symptoms are related to food intake that when limited to a low FODMAP diet achieves improvement in both symptoms and the quality of life in 50% to 76% of IBS patients.7

Implementing the low FODMAP diet

Where possible, a trained dietician should help you to develop a low-FODMAP diet. First, you should visit your doctor, who will then refer you. To help you stick to this diet, more investigations are needed to determine whether you can benefit from a low-FODMAP diet and to determine the FODMAP content of various foods. If you choose to try this diet, you should pass through three phases:9

Elimination phase

This phase can take from 2 weeks to 6 weeks. It entails staying away from most of the food known to be high in FODMAPs and observing whether symptoms subside or not and how frequently you suffer from them. There is a good chance that you will feel relieved and better, but that's not going to be permanent as you will have to introduce some of this high FODMAP food in a small amount later in the reintroduction phase to see how you will respond to it after the inflammation of the bowel has subsided.

Reintroduction phase 

In this phase, which usually lasts 8 weeks, your dietician will keep you on your low FODMAP diet but introduce one of the high FODMAP foods from each category, one at a time. To determine your tolerance level, you'll test each food in increasing amounts over a few days. To prevent any crossover effects, you will return to your basic low FODMAP diet for a few days in between each test. 

Maintenance phase 

In this phase, you can create a sustainable, nutrient-dense food plan with your healthcare physician that you can follow for a long time, or until you feel the need to retest, once you determine what works and what doesn't for you.

Challenges and considerations

Nevertheless, low-FODMAP diets have a few drawbacks that you should learn about, these drawbacks are increased if you follow the diet without professional advice:10

  • A low FODMAP diet is complex to understand and needs professional follow-up for proper implementation
  • Needs dedication to be accepted
  • Hard to apply in some environments such as travelling, or when going out with some friends
  • High cost and dull flavour of food
  • The FODMAP content of most foods is not listed
  • Reduction in the normal bacterial gut flora that is beneficial to produce vitamin K, helps in the digestion of cellulose and supports the formation of small capillaries among other things11
  • Constipation can occur if the fibres and vegetables that were ordinarily taken in a normal diet are not replaced with low FODMAP alternative
  • Being a restrictive diet, it can cause some nutritional deficiencies such as iron, vitamin C, natural antioxidants and lastly calcium whose main source is dairy products12 
  • Inadequate studies have been published on its long-term efficacy to determine its therapeutic activity in such a chronic and recurrent disease as IBS13

What is beyond the low FODMAP diet?

If you want another diet than the low FODMAP diet because you are not convinced or do not want to handle its drawbacks, you may benefit from several different diets. One of the diets recognised as a “standard” diet for treating IBS is the UK National Institute for Health and Clinical Excellence (NICE) diet. Approximately half of IBS patients (46% to 54%) respond similarly to the modified NICE diet to a low-FODMAP diet; however, the NICE diet is simpler to follow and does not carry the same risks. 

The British Dietetic Association initially suggested the modified NICE diet for those with IBS. Within the modified NICE diet, patients are encouraged to eat regular meals; substitute spelt products for wheat products; cut back on fatty foods, onions, cabbage, and beans; stay away from carbonated drinks and sweeteners that end in "-ol"; and regularly take psyllium husk fibres. Also, cutting back on alcohol, caffeine, and spicy foods is advised by the British Dietetic Association.3


The low FODMAP diet has been recognised as an effective approach for managing digestive disorders such as irritable bowel syndrome (IBS), irritable bowel disease (IBD), diverticulitis, and celiac disease. FODMAPs, which stands for fermentable oligo-, di-, monosaccharides, and polyols, are carbohydrates that can cause digestive symptoms when poorly absorbed in the gut. This diet focuses on reducing intake of high FODMAP food like certain dairy products, wheat-based products, beans, some vegetables, and fruits while emphasizing low FODMAP options such as eggs, meat, certain cheeses, almond milk, grains like rice and quinoa, and select fruits and vegetables.

The efficacy of the low FODMAP diet has been extensively studied, particularly in IBS patients, where it has shown significant symptom improvement. Implementation of the diet involves three phases: elimination, reintroduction, and maintenance, with guidance from a trained dietitian being crucial for proper execution. Despite its effectiveness, the diet presents challenges such as complexity, dedication required, difficulty in social situations, potential nutritional deficiencies, and lack of long-term efficacy studies.

If it does not work, then it's not for you. If you prefer alternatives to the low FODMAP diet, options like the modified NICE diet and other diets are available. Remember that you should seek medical advice before committing to any diet and make sure that you are professionally monitored.


  1. Kunzah Syed, Iswara K. Low-fodmap diet. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Feb 4]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK562224/
  2. Iacovou M, Tan V, Muir JG, Gibson PR. The low fodmap diet and its application in East and Southeast Asia. J Neurogastroenterol Motil. 2015 Oct 1;21(4):459–70. Available from: https://pubmed.ncbi.nlm.nih.gov/26350937/.
  3. Bellini M, Tonarelli S, Nagy AG, Pancetti A, Costa F, Ricchiuti A, et al. Low fodmap diet: evidence, doubts, and hopes. Nutrients [Internet]. 2020 Jan 4 [cited 2024 Feb 6];12(1):148. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7019579/
  4. Wu J, Masuy I, Biesiekierski JR, Fitzke HE, Parikh C, Schofield L, et al. Gut‐brain axis dysfunction underlies FODMAP-induced symptom generation in irritable bowel syndrome. Aliment Pharmacol Ther [Internet]. 2022 Mar [cited 2024 Feb 6];55(6):670–82. Available from: https://onlinelibrary.wiley.com/doi/10.1111/apt.16812
  5. Stasi C, editor. The complex interplay between gut-brain, gut-liver, and liver-brain axes. London: Academic Press; 2021. 247.  Available from: https://shop.elsevier.com/books/the-complex-interplay-between-gut-brain-gut-liver-and-liver-brain-axes/stasi/978-0-12-821927-0
  6. Gibson PR. History of the low FODMAP diet. J of Gastro and Hepatol [Internet]. 2017 Mar [cited 2024 Feb 7];32(S1):5–7. Available from: https://onlinelibrary.wiley.com/doi/10.1111/jgh.13685
  7. El-Salhy M, Patcharatrakul T, Gonlachanvit S. The role of diet in the pathophysiology and management of irritable bowel syndrome. Indian J Gastroenterol [Internet]. 2021 [cited 2024 Feb 7];40(2):111–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8187226/
  8. Magge S, Lembo A. Low-fodmap diet for treatment of irritable bowel syndrome. Gastroenterol Hepatol (N Y) [Internet]. 2012 Nov [cited 2024 Feb 7];8(11):739–45. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3966170/
  9. Sultan N, Varney JE, Halmos EP, Biesiekierski JR, Yao CK, Muir JG, et al. How to Implement the 3-Phase FODMAP Diet Into Gastroenterological Practice. J Neurogastroenterol Motil [Internet]. 2022 [cited 2024 Mar 14]; 28(3):343–56. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9274476/.
  10. O’Keeffe M, Lomer MC. Who should deliver the low FODMAP diet and what educational methods are optimal: a review. J Gastroenterol Hepatol. 2017 Mar;32 Suppl 1:23–6. Available from: https://pubmed.ncbi.nlm.nih.gov/28244661/.
  11. Zhang YJ, Li S, Gan RY, Zhou T, Xu DP, Li HB. Impacts of gut bacteria on human health and diseases. Int J Mol Sci [Internet]. 2015 Apr 2 [cited 2024 Feb 8];16(4):7493–519. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425030/
  12. O’Keeffe M, Jansen C, Martin L, Williams M, Seamark L, Staudacher HM, et al. Long‐term impact of the low-FODMAP diet on gastrointestinal symptoms, dietary intake, patient acceptability, and healthcare utilization in irritable bowel syndrome. Neurogastroenterology Motil [Internet]. 2018 Jan [cited 2024 Feb 8];30(1):e13154. Available from: https://onlinelibrary.wiley.com/doi/10.1111/nmo.13154
  13. Weynants A, Goossens L, Genetello M, De Looze D, Van Winckel M. The long‐term effect and adherence of a low fermentable oligosaccharides disaccharides monosaccharides and polyols (Fodmap) diet in patients with irritable bowel syndrome. J Human Nutrition Diet [Internet]. 2020 Apr [cited 2024 Feb 8];33(2):159–69. Available from: https://onlinelibrary.wiley.com/doi/10.1111/jhn.12706

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Rana Ibrahim

Masters of Critical care - Faculty of Medicine, Alexandria University, Egypt

Rana is a qualified medical professional specialising in critical care medicine. She has several years of expertise in the profession and a consistent commitment to clinical excellence and patient care. She has lately been involved in medical writing, driven by her recently discovered passion, using her knowledge and perceptions to teach and educate members of the medical community as well as the society as a whole.

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