Using the FODMAP Diet in IBD
by: Dr Adam P. Levine BSc (Hons), MBBS, PhD Honorary Research Associate and Academic Foundation Doctor
There have recently been two interesting studies published investigating “fermentable carbohydrates” (FODMAPs – fermentable, oligosaccharides, disaccharides, monosaccharides and polyols) in patients with Inflammatory Bowel Disease (IBD).
By definition, patients with IBD will go through periods of time when their disease is in ‘remission’ in which intestinal inflammation is well controlled and symptoms arising from this are minimal. During such times however, a significant number of patients (approximately 35%) will continue to suffer from gastrointestinal symptoms such as bloating, abdominal pain, and diarrhoea. These symptoms are typical of irritable bowel syndrome (IBS) and can significantly impair quality of life.
In patients with IBS, there is good evidence that restricting dietary intake of FODMAPs can improve symptoms in up to 70% of individuals. It is thought that this is due to FODMAPs causing increased amounts of water in the small bowel or by being incompletely digested and undergoing bacterial fermentation in the colon, producing gas.
Whilst preliminary data for the benefit of a low FODMAP diet in controlling so called ‘functional’ gastrointestinal symptoms in patients with IBD have been encouraging, until recently there have not been any randomised, blinded and placebo-controlled studies. Such studies are very important to ensure that the intervention (in this case, the low FODMAP diet) is responsible for making the patient’s symptoms better, rather than a ‘confounder’ (something else that is different between those receiving the low FODMAP diet and those not) or a ‘placebo effect’.
The first study, undertaken in London by Cox et al., recruited IBD patients that were in remission but continued to have symptoms of IBS. The individuals had all previously experienced an improvement in their symptoms from following a low FODMAP diet. Rather than test whether a low FODMAP diet improved the patients’ symptoms, this study examined the inverse: whether having high doses of FODMAPs exacerbated their symptoms. The patients in the trial each received a three day course of three different types of FODMAP or a placebo. The study found that fructans in particular (one of the types of FODMAP tested), was associated with significantly greater abdominal pain, bloating, flatulence and urgency. These findings suggest that eliminating FODMAPs (particularly fructans) in IBD patients in remission with IBS-like symptoms could be of benefit.
The second study, undertaken by Pedersen et al. in Denmark, also recruited IBD patients that were in remission but had symptoms of IBS. Patients were randomised to either follow a low FODMAP diet or their normal diet for a six week period, during which time their symptoms were monitored. They found that individuals following the low FODMAP diet were much more likely to have a significant reduction in their IBS-like symptoms than those continuing with their normal diet (81% versus 46%). Furthermore, the patients on the low FODMAP diet had a quantitative improvement in their ‘quality of life’ scores.
Both of these studies utilised relatively small numbers of patients (29 and 89, respectively). The Danish trial suffered from the lack of blinding and a placebo control group; those not receiving the low FODMAP diet would have been able to research and follow the diet themselves. However, at the end of the study, the patients following the low FODMAP diet reported significantly less FODMAP intake than the control patients.
These studies have robustly demonstrated (i) the ability of FODMAPs (particularly fructans) to worsen IBS-like symptoms in IBD patients and (ii) the ability of a low FODMAP diet to improve IBS-like symptoms. Further research, ideally with blinding and placebo groups including larger numbers of patients will be required to prove this, but these findings are certainly encouraging. It is important to recognise that they apply only to IBS-like symptoms in IBD patients in remission and not active IBD.
Finally, the use of restrictive diets such as low FODMAP have the potential to compromise nutritional intake and their use should be undertaken with professional advice.
1. Cox SR et al. Fermentable Carbohydrates [FODMAPs] Exacerbate Functional Gastrointestinal Symptoms in Patients With Inflammatory Bowel Disease: A Randomised, Double-blind, Placebo-controlled, Cross-over, Re-challenge Trial. Journal of Crohn’s and Colitis. 2017, 1-10.
2. Pedersen N et al., Low-FODMAP diet reduces irritable bowel syndromes in patients with Inflammatory Bowel Disease. World Journal of Gastroenterology. 2017,23(18):3356-3366.