A low-FODMAP diet consists in the global restriction of all fermentable carbohydrates (FODMAPs), that is recommended only for a short time. A low-FODMAP diet is recommended for managing patients with irritable bowel syndrome (IBS) and can reduce digestive symptoms of IBS including bloating and flatulence.
Effectiveness and risks
A low-FODMAP diet might help to improve short-term digestive symptoms in adults with irritable bowel syndrome, but its long-term use can have negative effects because it causes a detrimental impact on the gut microbiota and metabolome. It should only be used for short periods of time and under the advice of a specialist. More studies are needed to evaluate its effectiveness in children with irritable bowel syndrome. There is only a little evidence of its effectiveness in treating functional symptoms in inflammatory bowel disease from small studies that are susceptible to bias. More studies are needed to assess the true impact of this diet on health.
In addition, the use of a low-FODMAP diet without medical advice can lead to serious health risks, including nutritional deficiencies and misdiagnosis, so it is advisable to conduct a complete medical evaluation before starting a low-FODMAP diet to ensure a correct diagnosis and that the appropriate therapy may be undertaken.
Since the consumption of gluten is suppressed or reduced with a low-FODMAP diet, the improvement of the digestive symptoms with this diet may not be related to the withdrawal of the FODMAPs, but of gluten, indicating the presence of an unrecognized celiac disease, avoiding its diagnosis and correct treatment, with the consequent risk of several serious health complications, including various types of cancer.
A low-FODMAP diet is highly restrictive in various groups of nutrients, can be impractical to follow in the long-term and may add an unnecessary financial burden.
- Vegetables: alfalfa, bean sprouts, green beans, bok choy, capsicum (bell pepper), carrot, chives, fresh herbs, choy sum, cucumber, lettuce, tomato, zucchini, the green parts of leeks and spring onions
- Fruits: orange, grapes, melon
- Protein: meats, fish, chicken, eggs, tofu (not silken), tempeh
- Dairy: lactose-free milk, lactose-free yoghurts, hard cheese
- Breads and cereals: rice, crisped rice, maize or corn, potatoes, quinoa, and breads made with their flours alone; however, oats and spelt are relatively low in FODMAPs
- Biscuits (cookies) and snacks: made with flour of cereals listed above, without high FODMAP ingredients added (such as onion, pear, honey, or polyol artificial sweeteners )
- Nuts and seeds: almonds (no more than ten nuts per serving), pumpkin seeds; not cashews or pistachios
- Beverage options: water, coffee, tea
Other sources confirm the suitability of these and suggest some additional foods.
The basis of many functional gastrointestinal disorders (FGIDs) is distension of the intestinal lumen. Such luminal distension may induce pain, a sensation of bloating, abdominal distension and motility disorders. Therapeutic approaches seek to reduce factors that lead to distension, particularly of the distal small and proximal large intestine. Food substances that can induce distension are those that are poorly absorbed in the proximal small intestine, osmotically active, and fermented by intestinal bacteria with hydrogen (as opposed to methane) production. The small molecule FODMAPs exhibit these characteristics.
Over many years, there have been multiple observations that ingestion of certain short-chain carbohydrates, including lactose, fructose and sorbitol, fructans and galactooligosaccharides, can induce gastrointestinal discomfort similar to that of people with irritable bowel syndrome. These studies also showed that dietary restriction of short-chain carbohydrates was associated with symptoms improvement.
These short-chain carbohydrates (lactose, fructose and sorbitol, fructans and GOS) behave similarly in the intestine. Firstly, being small molecules and either poorly absorbed or not absorbed at all, they drag water into the intestine via osmosis. Secondly, these molecules are readily fermented by colonic bacteria, so upon malabsorption in the small intestine they enter the large intestine where they generate gases (hydrogen, carbon dioxide and methane). The dual actions of these carbohydrates cause an expansion in volume of intestinal contents, which stretches the intestinal wall and stimulates nerves in the gut. It is this 'stretching' that triggers the sensations of pain and discomfort that are commonly experienced by IBS sufferers.
The FODMAP concept was first published in 2005 as part of a hypothesis paper. In this paper, it was proposed that a collective reduction in the dietary intake of all indigestible or slowly absorbed, short-chain carbohydrates would minimise stretching of the intestinal wall. This was proposed to reduce stimulation of the gut's nervous system and provide the best chance of reducing symptom generation in people with IBS (see below). At the time, there was no collective term for indigestible or slowly absorbed, short-chain carbohydrates, so the term 'FODMAP' was created to improve understanding and facilitate communication of the concept.
The low FODMAP diet was originally developed by a research team at Monash University in Melbourne, Australia. The Monash team undertook the first research to investigate whether a low FODMAP diet improved symptom control in patients with IBS and established the mechanism by which the diet exerted its effect. Monash University also established a rigorous food analysis program to measure the FODMAP content of a wide selection of Australian and international foods. The FODMAP composition data generated by Monash University updated previous data that was based on limited literature, with guesses (sometimes wrong) made where there was little information.
- Gibson PR, Shepherd SJ (February 2010). "Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach". Journal of Gastroenterology and Hepatology. 25 (2): 252–8. doi:10.1111/j.1440-1746.2009.06149.x. PMID 20136989.
Wheat is a major source of fructans in the diet. (...) Table 1 Food sources of FODMAPs. (...) Oligosaccharides (fructans and/or galactans). Cereals: wheat & rye when eaten in large amounts (e.g. bread, pasta, couscous, crackers, biscuits)
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- Turco R, Salvatore S, Miele E, Romano C, Marseglia GL, Staiano A (May 2018). "Does a low FODMAPs diet reduce symptoms of functional abdominal pain disorders? A systematic review in adult and paediatric population, on behalf of Italian Society of Pediatrics". Italian Journal of Pediatrics (Systematic Review). 44 (1): 53. doi:10.1186/s13052-018-0495-8. PMC 5952847. PMID 29764491.
- Staudacher HM, Irving PM, Lomer MC, Whelan K (April 2014). "Mechanisms and efficacy of dietary FODMAP restriction in IBS". Nature Reviews. Gastroenterology & Hepatology (Review). 11 (4): 256–66. doi:10.1038/nrgastro.2013.259. PMID 24445613.
An emerging body of research now demonstrates the efficacy of fermentable carbohydrate restriction in IBS. [...] However, further work is urgently needed both to confirm clinical efficacy of fermentable carbohydrate restriction in a variety of clinical subgroups and to fully characterize the effect on the gut microbiota and the colonic environ¬ment. Whether the effect on luminal bifidobacteria is clinically relevant, preventable, or long lasting, needs to be investigated. The influence on nutrient intake, dietary diversity that might also affect the gut microbiota, and quality of life also requires further exploration as does the possible economic effects due to reduced physician contact and need for medication. Although further work is required to confirm its place in IBS and functional bowel disorder clinical pathways, fermentable carbohydrate restriction is an important consideration for future national and international IBS guidelines.
- Marsh A, Eslick EM, Eslick GD (April 2016). "Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis". European Journal of Nutrition. 55 (3): 897–906. doi:10.1007/s00394-015-0922-1. PMID 25982757.
- Rao SS, Yu S, Fedewa A (June 2015). "Systematic review: dietary fibre and FODMAP-restricted diet in the management of constipation and irritable bowel syndrome". Alimentary Pharmacology & Therapeutics. 41 (12): 1256–70. doi:10.1111/apt.13167. PMID 25903636.
- Tuck CJ, Muir JG, Barrett JS, Gibson PR (September 2014). "Fermentable oligosaccharides, disaccharides, monosaccharides and polyols: role in irritable bowel syndrome". Expert Review of Gastroenterology & Hepatology. 8 (7): 819–34. doi:10.1586/17474124.2014.917956. PMID 24830318.
- Heiman ML, Greenway FL (May 2016). "A healthy gastrointestinal microbiome is dependent on dietary diversity". Molecular Metabolism (Review). 5 (5): 317–320. doi:10.1016/j.molmet.2016.02.005. PMC 4837298. PMID 27110483.
- Staudacher HM, Whelan K (August 2017). "The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS". Gut (Review). 66 (8): 1517–1527. doi:10.1136/gutjnl-2017-313750. PMID 28592442.
- Gearry RB, Irving PM, Barrett JS, Nathan DM, Shepherd SJ, Gibson PR (February 2009). "Reduction of dietary poorly absorbed short-chain carbohydrates (FODMAPs) improves abdominal symptoms in patients with inflammatory bowel disease-a pilot study". Journal of Crohn's & Colitis. 3 (1): 8–14. doi:10.1016/j.crohns.2008.09.004. PMID 21172242.
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Even less evidence exists for the efficacy of the SCD, FODMAP, or Paleo diet. Furthermore, the practicality of maintaining these interventions over long periods of time is doubtful. At a practical level, adherence to defined diets may result in an unnecessary financial burden or reduction in overall caloric intake in patients who are already at risk for protein-calorie malnutrition.
- Barrett JS (March 2017). "How to institute the low-FODMAP diet". Journal of Gastroenterology and Hepatology (Review). 32 Suppl 1: 8–10. doi:10.1111/jgh.13686. PMID 28244669.
Common symptoms of IBS are bloating, abdominal pain, excessive flatus, constipation, diarrhea, or alternating bowel habit. These symptoms, however, are also common in the presentation of coeliac disease, inflammatory bowel disease, defecatory disorders, and colon cancer. Confirming the diagnosis is crucial so that appropriate therapy can be undertaken. Unfortunately, even in these alternate diagnoses, a change in diet restricting FODMAPs may improve symptoms and mask the fact that the correct diagnosis has not been made. This is the case with coeliac disease where a low-FODMAP diet can concurrently reduce dietary gluten, improving symptoms, and also affecting coeliac diagnostic indices. Misdiagnosis of intestinal diseases can lead to secondary problems such as nutritional deficiencies, cancer risk, or even mortality in the case of colon cancer.
- "Celiac disease". World Gastroenterology Organisation Global Guidelines. July 2016. Archived from the original on 17 March 2017. Retrieved 4 June 2018.
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- Barrett JS, Gearry RB, Muir JG, Irving PM, Rose R, Rosella O, Haines ML, Shepherd SJ, Gibson PR (April 2010). "Dietary poorly absorbed, short-chain carbohydrates increase delivery of water and fermentable substrates to the proximal colon". Alimentary Pharmacology & Therapeutics. 31 (8): 874–82. doi:10.1111/j.1365-2036.2010.04237.x. PMID 20102355.
- Muir JG, Rose R, Rosella O, Liels K, Barrett JS, Shepherd SJ, Gibson PR (January 2009). "Measurement of short-chain carbohydrates in common Australian vegetables and fruits by high-performance liquid chromatography (HPLC)". Journal of Agricultural and Food Chemistry. 57 (2): 554–65. doi:10.1021/jf802700e. PMID 19123815.
- Muir JG, Shepherd SJ, Rosella O, Rose R, Barrett JS, Gibson PR (August 2007). "Fructan and free fructose content of common Australian vegetables and fruit". Journal of Agricultural and Food Chemistry. 55 (16): 6619–27. doi:10.1021/jf070623x. PMID 17625872.
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- A Beginner's Guide to the Low-FODMAP Diet at HealthLine