Advisement on diet is important when it comes to functional gastrointestinal disorders (FGID). This is a challenging task for clinicians, physician as it seems that the underlying cause is resided within the nervous system, representing diet as one of the triggering factors for symptoms.  Science now reveals good evidence on restricting FODMAPs from the diet on controlling symptoms e.g. with subjects suffering from irritable bowel syndrome.[1]

FODMAPs and Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome is more commonly related to food intolerances leading to symptom induction according to many patients.[2]  FODMAP stands for fermentable oligosaccharides, disaccharides, mono-saccharides and polyols.  Oligo-saccharides are fructans and galactooligo-saccharides (GOS).  Di-saccharide is lactose, mono-saccharide is fructose and polyols are sorbitol and mannitol.  These are thought to have an effect on the digestive system through their osmotic effects and fermentation.  Symptoms are e.g. boating, wind, abdominal pain and in some cases diarrhea or constipation, which are all known symptoms in IBS.[3],[4]  IBS is a functional bowel/gut disorder and is defined as “…functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit, and with features of disordered defecation.” according to Longstreth et al.[5]

FERMENTABLE Carbohydrates (FODMAPs) and Digestion

FODMAPs are short chain carbohydrates that seem to trigger functional gut symptoms in three out of four subjects suffering from IBS.[6]  The hypothesis is that these carbohydrates are poorly absorbed in the small intestine and gastro-intestinal symptoms can be triggered in subjects with abnormal motility responses or visceral hypersensitivity.[7],[8]  Symptoms are triggered by gas production and osmotic effects which induces luminal distension in the intestines, luminal distension largely responsible for functional gut symptoms. FODMAPs are rapidly fermented by the bacteria in the small intestines and in the proximal colon, resulting in increased gas production.Poor absorption of small molecules from the diet is likely to create symptoms, which will most likely be generated in the proximal colon and the distal small intestine.[9]

BREATH Hydrogen Test

Breath hydrogen testing is a useful tool to define if the subject can absorb fructose and/or lactose.  This can be done to determine the degree of dietary restriction.  Humans generally malabsorb other FODMAP (oligosaccharides and polyols).  In some patients fructose and lactose are malabsorbed.[10],[11]  Humans generally don´t absorb polyols, e.g. sorbitol, very well[12] nor fructo-oligosaccharides (fructans).  Galacto-oligosaccharides (raffinose) are poorly absorbed on the basis of lack of suitable hydrolases.[13]  Up to 36% of the European population suffers from fructose malabsorption (FM) and 50% of those are symptomatic.[14]  Breath hydrogen test is a diagnostic tool for FM.  An oral load of fructose is provided and H2 concentration is measured in exhaled breath.[15]


In a study by Ong et al[16] breath hydrogen production was grater in IBS subjects compared to controls on high FODMAPs diet.  Subjects suffering from IBS experienced increased bloating, flatulence and abdominal pain when put on high FODMAPs diet.  According to Barrett et al[17] in a recent study in ileostomates, diet high in FODMAPs is more likely to increase the amount of liquid and fermentable substrates that are rapidly delivered to the proximal colon. Abdominal symptoms from FODMAPs diet are well documented.  Sorbitol, fructose or sorbitol and fructose together, lactose and fructo-oligosaccharides are all known to induce abdominal pain and bloating and to increased wind as well as induce diarrhea.[18],[19],[20],[21],[22]

In a randomized controlled trial study[23] on the gastrointestinal microbiota, by restricting fermentable short chain carbohydrates, the findings reveled effective management of IBS symptoms.  Reduction was seen with symptoms like bloating, pain, wind, diarrhea, constipation, nausea and energy levels were improved.  Interestingly, luminal bifidobacterial concentration was reduced as well as their proportion but these findings are in paradox with previous findings on improvements on IBS with bifidobactera probiotics.[24]  According to Shepherd et al[25] subjects with IBS and FM symptoms were improved when put on fructose and/or fructans restricted diet.  Symptoms were reintroduced when re-challenged with fructose or fructans or both together.  These findings suggest poor absorption of short-chain carbohydrates inducing symptoms in IBS subjects.

DIET high in FODMAPs

Oligosaccharides are frucans and galacto-oligosaccharides (GOS).  Fructans are found in onion, brassica family, wheat and rye.  Beans, peas and pulses are example of GOS. Sugar-free gum contains sorbitol, which is a polyol.  Another example of polyols are pears apples and other stone fruits, containing mannitol. Fructose is a monosaccharide.  Agave syrup, honey, mango, apple and pear contain fructose. Lactose is a disaccharide and is found in milk and dairy products.

FODMAPs Excluded in a “Low FODMAP Diet”


Oligo-saccharides = Fructans and GOS.  Malabsorbed by all humans.

Di-saccharides = lactose.  Excluded in low FODMAPs diet if lactase deficient.

Mono-saccharides = fructose.  Always excluded in low FODMAPs diet.


Polyols = sorbitol and mannitol.  Malabsorbed by all humans.

It is important to exclude all foods high in those FODMAPs for a given time and then re-challenge at later date in smaller amounts.  If symptoms reappear it is advisable to avoid all foods high in that particular FODMAP.  FODMAPs tables give limited information on whether diet contains high amounts of FODMAPS or not as the cut off is not totally clear.  It is important to look at the amount digested in one meal on a total basis (not the individual FODMAPs) in relation to induced symptoms.  Foods that has been reported to produce symptoms: Foods/beverages containing >0.5g fructose in excess of glucose per/100g and >0.2 g of fructans per/serving are “at risk” of produce symptoms.


Advisement on diet is important when it comes to functional gastrointestinal disorders.  In IBS cases evidence reveal good effect on low FODMAPs diet to reduce symptoms. To determine the degree of dietary restriction, breath hydrogen testing can be performed for fructose and/or lactose but generally humans do not absorb oligosaccharides and polyols well.  Without hydrogen breath tests it is important to exclude all fermentable, short chain carbohydrates i.e. FODMAPs from the diet for a given time and then re-introduce them to see if symptoms are provoked.   There are evidence suggesting on incomplete information on FODMAPs lists and emphasize on amount of FODMAPs in the meal in relation to symptom induction, but overall research has revealed good evidence for using low FODMAPs diet in cases of IBS.

Copyright @ Jörth 2008-2017


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Copyright @ Jörth 2008-2017