Have you heard about the low-FODMAP diet, but have no idea what it is? This week’s blog attempts to shed some light on clarifying what FODMAPs are and why they are important for anyone with a history of digestive disorders (referred herein as IBS).

Reducing or eliminating food intolerances for managing IBS symptoms has been gaining momentum in health-conscious circles for decades. While dietary modifications are not a cure for IBS, they can improve symptoms and quality of life. In particular, the low-FODMAP diet has been shown to improve symptoms in at least 74% of patients with IBS. Non-celiac gluten intolerance has been reported (1), but further research is needed to identify the underlying mechanism. The relative ease of implementing the low-FODMAP diet combined with considerable evidence supporting its effectiveness suggests the low-FODMAP diet should be the first dietary approach in people diagnosed with IBS.

What are FODMAPs?

FODMAPs are short-chain carbohydrates and related alcohols that are poorly absorbed in the small intestine. The term FODMAP is an acronym, derived from “Fermentable Oligo-, Di-, Mono-saccharides And Polyols” (2). The low FODMAP diet was developed at Monash University in Melbourne by Peter Gibson and Susan Shepherd (3,4).

How was the low-FODMAP diet discovered?

Throughout the 1980s and 1990s, evidence was building for the role of poorly absorbed, short-chain carbohydrates (lactose and fructose) in inducing IBS symptoms, with dietary restriction providing symptomatic relief (5-8). It was clear, however, that these sugars were not the only culprits. Other short-chain carbohydrates were identified as poorly absorbed in the human GI tract, such as fructo-oligosaccharides (fructans), galacto-oligosaccharides (GOS), and sugar polyols, sorbitol and mannitol (artificial sweeteners also found naturally in some foods).

Gibson and Shepherd were the first to publish a description of FODMAPs in 2005 (9) with the first published research trial in 2006 (10). A total of 74% of patients reported symptomatic improvement on the low-FODMAP dietary regimen. The efficacy of the low-FODMAP diet was confirmed and reconfirmed in subsequent trials and studies (11, 12).

Two additional trials (13, 14) identified the mechanisms that explained the gastrointestinal (GI) effects of FODMAPs: poor absorption in the small intestine, increased water content of the output (explaining why some experience diarrhea), and fermentation of the short-chain carbohydrates, which induced bloating, distension, abdominal pain and excessive flatulence. The low-FODMAP diet reduces fermentation and associated gas production, which is likely to reduce symptom severity of IBS patients.

Other potential factors include alterations in the gut microbiota number, composition, function and location. Some patients with IBS have small intestine bacterial overgrowth (SIBO) with fermentation of malabsorbed carbohydrates occurring in the narrow lumen of the small intestine, the location of which may be associated with abdominal pain and discomfort. With more predominant methane-producing bacteria, fermenting malabsorbed carbohydrates would produce methane gas, which is linked to delayed transit and constipation (15-17).

Since these initial studies, the FODMAP approach has been fine-tuned to include GOS, sorbitol and mannitol, in addition to fructose, lactose and fructans. These six carbohydrates make up the low-FODMAP diet as it is today, with published tables of food composition available on fruits and vegetables and breads and cereals (18-20). The table below summarizes the richest FODMAP food sources.

FODMAP foods table60

What does this mean for you?

Not all FODMAPs will trigger symptoms and will depend on whether they are malabsorbed by the individual. Importantly, fructans and GOS are always malabsorbed and fermented by intestinal microflora (21-23) as are the sugar polyols, sorbitol and mannitol (24-27). Other FODMAP carbohydrates will only induce symptoms in the proportion of patients with IBS that malabsorb them.

Breath testing is useful for clarifying which FODMAP foods to avoid on an individual basis by providing a reliable measure of test sugar absorption via measurement of breath hydrogen lev­els (28). A significant rise in breath hydrogen following ingestion of the test sugar (e.g. fructose) demon­strates poor absorption with fermen­tation by intestinal microflora. Negative breath tests demonstrate complete absorption of the sugar and suggest that the patient can consume this sugar without a negative impact on their symptoms.

Commonly offered breath tests for detecting FODMAP intolerances are typically for fructose, lactose and sorbitol (28). Regardless of breath test results, there are three other FODMAP carbohydrates that need to be considered as potential triggers. Fructans and GOS are not breath tested as they are always mal­absorbed. They are always fermented and should be considered as triggers in all IBS patients. Mannitol is rarely offered as a breath test because it is not found widely in the diet and can be inves­tigated as a trigger through simple dietary elimi­nation and rechallenge (28).

The results from breath tests can be used to implement a low-FOD­MAP diet without restricting sugars shown to be well absorbed. This individu­alizes the diet and avoids unnecessary restrictions as well as assisting with the long-term nutritional composition of the diet (28). In addition, FODMAPs have prebiotic effects due to the production of short-chain fatty acids after fermentation. Therefore, everyone is encouraged to try and reintroduce FODMAPs to a level that they can comfortably tolerate (28).

  1. Biesiekierski, J.R., Newnham, E.D., Irving, P.M., Barrett, J.S., Haines, M., Doecke, J.D. et al. (2010) Gluten causes gastrointestinal symptoms in subjects without celiac disease: a double-blind randomized placebo-controlled trial. AmJ Gastroenterol 106: 508–514; quiz 515.
  2. Shepherd, S. (2013) Low FODMAP Recipes. Melbourne, Australia: Penguin. ISBN 9780143567561.
  3. FODMAPS. King’s College, London. Diabetes & Nutritional Sciences. http://www.kcl.ac.uk/lsm/research/divisions/dns/projects/fodmaps/index.aspx
  4. Gibson, P.R., Gibson, P.R., Shepherd, S.J. (2010). Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. Journal of Gastroenterology and Hepatology 25 (2): 252–258. doi:10.1111/j.1440-1746.2009.06149.x. PMID 20136989.
  5. Goldstein, R., Braverman, D. and Stankiewicz, H. (2000) Carbohydrate malabsorption and the effect of dietary restriction on symptoms of irritable bowel syndrome and functional bowel complaints. Isr Med Assoc J 2: 583–587.
  6. Nelis, G.F., Vermeeren, M.A. and Jansen, W. (1990) Role of fructose-sorbitol malabsorption in the irritable bowel syndrome. Gastroenterology 99: 1016–1020.
  7. Rumessen, J.J. and Gudmand-Hoyer, E. (1988) Functional bowel disease: malabsorption and abdominal distress after ingestion of fructose, sorbitol, and fructose-sorbitol mixtures. Gastroenterology 95: 694–700.
  8. Symons, P., Jones, M.P. and Kellow, J.E. (1992) Symptom provocation in irritable bowel syndrome. Effects of differing doses of fructose-sorbitol. Scand J Gastroenterol 27: 940–944.
  9. Gibson, P.R. and Shepherd, S.J. (2005) Personal view: food for thought – western lifestyle and susceptibility to Crohn’s disease. The FODMAP hypothesis. Aliment Pharmacol Ther 21: 1399–1409.
  10. Shepherd, S.J. and Gibson, P.R. (2006) Fructose malabsorption and symptoms of irritable bowel syndrome: guidelines for effective dietary management. J Am Diet Assoc 106: 1631–1639.
  11. Shepherd, S.J., Parker, S.C., Muir, J.G. and Gibson, P.R. (2008) Randomised, placebo-controlled evidence of dietary triggers for abdominal symptoms in patients with irritable bowel syndrome. Clin Gastroenterol Hepatol 6: 765–771.
  12. Staudacher, H.M., Whelan, K., Irving, P.M. and Lomer, M.C.E. (2011) Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet 24: 487–495.
  13. Barrett, J.S., Gearry, R.B., Muir, J.G., Irving, P.M., Rose, R., Rosella, O. et al. (2010) Dietary poorly absorbed, short-chain carbohydrates increase delivery of water and fermentable substrates to the proximal colon. Aliment Pharmacol Ther 31: 874–882.
  14. Ong, D.K., Mitchell, S.B., Barrett, J.S., Shepherd, S.J., Irving, P.M., Biesiekierski, J.R. et al. (2010) Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol 25: 1366–1373.
  15. Chatterjee, S., Park, S., Low, K., Kong, Y. and Pimentel, M. (2007) The degree of breath methane production in IBS correlates with the severity of constipation. Am J Gastroenterol 102: 837–841.
  16. Fiedorek, S.C., Pumphrey, C.L. and Casteel, H.B. (1990) Breath methane production in children with constipation and encopresis. J Pediatr Gastroenterol Nutr 10: 473–477.
  17. Pimentel, M., Lin, H.C., Enayati, P., van den Burg, B., Lee, H.R., Chen, J.H. et al. (2006) Methane, a gas produced by enteric bacteria, slows intestinal transit and augments small intestinal contractile activity. Am J Physiol Gastrointest Liver Physiol 290: G1089–G1095.
  18. Pimentel, M., Mayer, A.G., Park, S., Chow, E.J., Hasan, A. and Kong, Y. (2003) Methane production during lactulose breath test is associated with gastrointestinal disease presentation. Dig Dis Sci 48: 86–92.
  19. Biesiekierski, J.R., Rosella, O., Rose, R., Liels, K., Barrett, J.S., Shepherd, S.J. et al. (2011) Quantification of fructans, galacto-oligosacharides and other short-chain carbohydrates in processed grains and cereals. J Hum Nutr Diet 24: 154–176.
  20. Muir, J., Rose, R., Rosella, O., Liels, K., Barrett, J., Shepherd, S. et al. (2009) Measurement of short chain carbohydrates (FODMAPs) in common Australian vegetables and fruit by high performance liquid chromatography. J Agric Food Chem 57: 554–565.
  21. Muir, J.G., Shepherd, S.J., Rosella, O., Rose, R., Barrett, J.S. and Gibson, P.R. (2007) Fructan and free fructose content of common Australian vegetables and fruit. J Agric Food Chem 55: 6619–6627.
  22. Macfarlane, G., Steed, H. and Macfarlane, S. (2008) Bacterial metabolism and health-related effects of galacto-oligosaccharides and other prebiotics. J Appl Microbiol 104: 305–344.
  23. Rumessen, J.J. and Gudmand-Hoyer, E. (1998) Fructans of chicory: intestinal transport and fermentation of different chain lengths and relation to fructose and sorbitol malabsorption. Am J Clin Nutr 68: 357–364.
  24. Saunders, D.R. and Wiggins, H.S. (1981) Conservation of mannitol, lactulose, and raffinose by the human colon. Am J Physiol 241: G397–G402.
  25. Ong, D.K., Mitchell, S.B., Barrett, J.S., Shepherd, S.J., Irving, P.M., Biesiekierski, J.R. et al. (2010) Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol 25: 1366–1373.
  26. Evans, P.R., Piesse, C., Bak, Y.T. and Kellow, J.E. (1998) Fructose-sorbitol malabsorption and symptom provocation in irritable bowel syndrome: relationship to enteric hypersensitivity and dysmotility. Scand J Gastroenterol 33: 1158–1163.
  27. Fernandez-Banares, F., Esteve-Pardo, M., Humbert, P., de Leon, R., Llovet, J.M. and Gassull, M.A. (1991) Role of fructose-sorbitol malabsorption in the irritable bowel syndrome. Gastroenterology 101: 1453–1454.
  28. Barrett, J.S. and Gibson, P.R. (2012) Fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) and nonallergic food intolerance: FODMAPs or food chemicals? Ther Adv Gastroenterol 5(4) 261–268. DOI: 10.1177/ 1756283X11436241