In some individuals eating of certain short-chain carbohydrates, such as lactose, fructose, fructo-oligosaccharides, galacto-oligosaccharides and sorbitol leads to symptoms similar to functional GI disorders, including Irritable Bowel Syndrome. It is not clear whether functional gastrointestinal disorders are partially caused by an intolerance reaction to eating these carbohydrates, or whether they are separate co-existing conditions. Some of the intolerance symptoms are caused by distention (stretching) of the intestines by gas and liquid, others probably by increased sensitivity to food ingredients. Fermentation of incompletely absorbed food by the intestinal flora (microbiome) is likely to play an important role.
In the FODMAP intolerance hypothesis, all types of fermentable short-chain carbohydrates in the diet are reduced together, as it is postulated that the combined approach results in superior symptom relief to a reduction of individual carbohydrates.
In practice, even in the FODMAP diet an individual adaptation to those fermentable carbohydrates causing most symptoms is advocated. This is advisable, as long term adherence to a strict FODMAP diet risks leading to nutritional deficiencies and possibly to negative effects on the intestinal microbiome
Frequency in population and natural history
In the largest study investigating the incidence of FODMAP intolerances to date (PDF Download),
we showed that 33% of patients with functional gastrointestinal disorders had a FODMAP intolerance, with no differences in prevalence between the different types of syndromes, such as IBS and functional dyspepsia.
However, it was also shown, that 60% of all patients had fructose intolerance and 51% had lactose intolerance, indicating that a general reduction of FODMAPs is not necessary in a considerable number of patients with functional gastrointestinal disorders or IBS. Long term observations of the natural course of FODMAP disorders have not been reported, but lactose and fructose intolerance appear to be long term conditions requiring long term dietary changes.
Common symptoms are bloating, abdominal cramps and pain, diarrhea or constipation, increased intestinal sounds and gas production, reflux (e.g. acid taste in mouth, heartburn) and nausea.
The symptoms resemble those of functional disorders or Irritable Bowel Syndrome (IBS).
Testing and diagnosis
There is no specific collective test for FODMAP intolerances, but the individual short-chain carbohydrate intolerances, such as lactose, fructose, fructan and sorbitol intolerances, can be tested by breath testing.
For more information of these intolerance tests:
The FODMAP diet advocates strict reduction of the fermentable short-chain carbohydrates for 4–6 weeks under supervision of a trained dietician. No or minimal response should lead to the abandonment of the FODMAP diet. In case of a good response, individualization of the amount and of the type of carbohydrate restricted is performed during a structured food reintroduction phase.
Studies show this approach to achieve satisfactory symptom relief in 70% of patients with IBS and in over 80% of patients with functional gastrointestinal disorders and proven food intolerances by breath testing.
The onset of relief is within 7 days, but long term relief has not been documented for more than 6 weeks. Nutritional deficiencies should be monitored and supplementation of vitamins and minerals implemented as required.
Wilder-Smith CH et al.
Fructose and lactose intolerance and malabsorption testing: the relationship with symptoms in functional gastrointestinal disorders.
Aliment Pharmacol Ther 2013