By Lyndal McNamara (APD)
New research about the long-term effectiveness of a low-FODMAP diet to reduce the symptoms of irritable bowel syndrome (IBS) has just been published! This retrospective study provides data regarding the longest follow up to date of patients with IBS (some of which also had IBD) using the low FODMAP diet approach. One hundred and eighty patients were included in the study. All patients had been assessed by a gastroenterologist and previously received dietary education from a dietitian regarding a low FODMAP diet. Participants were surveyed to collect information about the effectiveness of the diet, symptoms, adherence to the diet, their satisfaction with dietary treatment, disease activity, changes in stool type and quality of life over an average follow-up time of 16 months.
The study found that 86% of patients had a significant improvement in their IBS symptoms on a low-FODMAP diet, with the greatest relief in symptoms of bloating and abdominal pain. Overall, stool form normalised with a low FODMAP diet in the majority of patients.
Adherence and satisfaction with the diet:
Eighty four percent of patients had expanded their low FODMAP diet at follow up, where some higher FODMAP foods had been re-introduced after the identification of trigger FODMAP foods. The most common foods not reintroduced by participants were wheat, onion and lactose containing products. Despite the fact that the vast majority were following a very relaxed version of the low FODMAP diet, they still reported satisfaction with the treatment and good symptom control.
IBS severity and quality of life:
Most patients reported good quality of life and only mild-moderate IBS severity at follow up. Furthermore, 37% of IBS patients who started the trial with more severe IBS (type B, C or D in graphs below) tended towards a milder IBS (type A) at follow-up. A similar effect was noted in the group with IBS in the setting of IBD.
A major limitation of this study was that it was conducted retrospectively, meaning that the results rely on the patients’ memory and recall of events, which introduces a potential source of error. A large percentage of patients (48%) invited to take part in the study also declined to participate. This introduces a type of bias known as selection bias, meaning that those who agreed to participate may be more likely to have had a positive experience with the diet being tested. Additionally, the researchers used tools that were not validated, such as the IBS severity graphs shown in the above figures. As these are not validated, they have not been tested for their accuracy and cannot be relied upon to form firm conclusions.
Take home messages:
· This is the first study to demonstrate the long-term effectiveness of a low-FODMAP diet for improved symptom management in IBS (alone or with coexisting IBD) patients
· This study also supports the importance of the reintroduction phase of the diet and demonstrates that for most patients, symptom management remains satisfactory on a modified low FODMAP diet in the long-term (where some high FODMAP foods have been successfully reintroduced)
· When looking at research studies, the tools used should be validated, and if not, outcomes should be read with caution
· This type of retrospective study has several important limitations that need to be considered
Larger, prospective trails are now required to further investigate the long-term effectiveness and determine other effects of a low FODMAP diet in IBS and IBD patients, particularly any negative effect on the gut microbiota
1. Maagaard L, Ankersen DV, Végh Z, Burisch J, Jensen L, Pedersen N, et al. Follow-up of patients with functional bowel symptoms treated with a low FODMAP diet. World Journal of Gastroenterology. 2016 Apr 21;22(15):4009-19.