Comorbid Fibromyalgia Does Not Impact Low FODMAP Diet Adherence, Outcomes for IBS

Massimo Bellini, MD

Credit: ResearchGate

Comorbid fibromyalgia does not influence long-term outcomes of or adherence to an adapted low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet in patients with irritable bowel syndrome (IBS), according to findings from a recent study.¹

“Dietary managements are among the most prescribed therapies for IBS and a low FODMAP diet is currently considered a ‘second line’ dietary management for IBS. However, some concerns have been raised regarding the low FODMAP diet,” Massimo Bellini, MD, an associate professor of medicine and head of the digestive physiopathology section of the gastroenterology unit at the University of Pisa, and colleagues wrote.¹ “ In order to overcome these possible limitations, a less restrictive diet based on the exclusion of only the food ‘triggers’ that patients recognize can be designed. However, adherence to a low FODMAP diet may be influenced by several factors: this diet can be difficult to teach, to learn, and also to continue in the long term.”

IBS is estimated to affect up to 15% of adults in the US.² Often, patients with IBS also experience fibromyalgia, underscoring the importance of considering its potential impact on the efficacy of and adherence to IBS care.¹

To assess differences in long-term adherence to an adapted low FODMAP diet and its clinical outcomes in IBS patients with and without fibromyalgia, investigators enrolled patients with IBS who were evaluated at the outpatient service of the Gastrointestinal Unit of the University of Pisa and subsequently referred to a nutritionist for the prescription of a low FODMAP diet. IBS was diagnosed based on Rome IV criteria, and if comorbid fibromyalgia was suspected, patients were referred to the division of rheumatology of the University of Pisa for confirmation or exclusion of fibromyalgia based on the 2016 revised fibromyalgia diagnostic criteria.¹

A total of 105 patients with IBS with and without comorbid fibromyalgia were referred to a nutritionist to start a low FODMAP diet, 41 of whom discontinued the diet because they felt it was not effective and 64 of whom proceeded to the adapted phase of the diet after 8 weeks based on their FODMAP intolerance. In total, 51 patients were reassessed to evaluate long-term outcomes and adherence.¹

Among the cohort, the mean age was 53.1 ± 13.3 years and the mean BMI was 24.5 ± 4.2 kg/m2. Most (62.7%) patients had IBS alone, whereas 37.3% had overlapping IBS–fibromyalgia.¹

Patients were evaluated by the IBS Symptom Severity Score (IBS-SSS), the Bristol Stool Form Chart (BSFC), a bowel habits questionnaire, and the Hospital Anxiety and Depression Scale (HADS) at baseline. After 8 weeks of the low FODMAP diet, responder patients proceeded to the adapted phase of the diet and were reassessed after a mean follow-up of 62.5 ± 22.7 months with the same tools as baseline as well as the FODMAP Adherence Report Scale (FARS), a “degree of relief from symptoms” Likert scale, and a “degree of treatment satisfaction” scale.¹

Investigators noted there were no differences in the frequency of comorbid fibromyalgia, IBS subtype, age, or gender between patients who did and did not respond to the initial strict low FODMAP diet. Additionally, there were no differences regarding the frequency of comorbid fibromyalgia, IBS subtype, age, or gender between patients who were and were not reassessed during follow-up.¹

In total, 30 patients reported a reduction in IBS-SSS symptom severity at follow-up compared with baseline and were considered long-term responders to the adapted low FODMAP diet. Despite some differences in individual IBS-SSS items, investigators noted comorbid fibromyalgia did not influence the total IBS-SSS score.¹

In total 41 (80.4%) participants reported scores of between 0 and 3 for symptom relief, with no significant differences observed between the IBS and IBS-fibromyalgia groups. Additionally, patients reported a mean treatment satisfaction of 8.0 ± 2.3, again with no differences based on the presence of fibromyalgia. Bowel habits questionnaire responses showed an overall reduction at follow-up compared with baseline in the mean frequency of abdominal pain (2.6 vs 1.5; P <.001), abdominal bloating (2.9 vs 2.3; P = .025), and watery stools (1.9 vs 1.5; P = .049).¹

At baseline, patients with IBS and fibromyalgia showed higher scores on both HAD-A and HAD-D subscales (P = .026 and P = .05, respectively). At follow-up, there were no differences in mean HAD-A or HAD-D scores between patients with and without fibromyalgia.¹

The mean FARS score for all patients at follow-up was 20.5 ± 5.2. In total, 44 (86.3%) patients showed good long-term adherence to the adapted low FODMAP diet (FARS score ≥ 20). Of note, there was no difference in the FARS mean scores between patients with and without fibromyalgia (20.4 ± 5.4 vs 20.5 ± 5.2, respectively; P = .943).¹

Investigators outlined multiple limitations to these findings, including the use of telephone interviews during follow-up; the inability to account for the severity of fibromyalgia; and the limited number of study participants due to the monocentric study design.¹

“Comorbid fibromyalgia had only a slight influence on the long-term outcomes of the adapted low FODMAP diet on IBS symptoms, without impacting global symptom relief and with no influence on long-term adherence to the adapted low FODMAP diet,” investigators concluded.¹ “Having comorbid fibromyalgia was not a predictive factor of better or worse long-term response nor adherence to the adapted low FODMAP diet. Therefore, this dietetic approach can be taken into account also in fibromyalgia patients for the nonpharmacological management of IBS symptoms.”

References

1. ^{Lambiase C, Rossi A, Morganti R, et al. Adapted Low-FODMAP Diet in IBS Patients with and without Fibromyalgia: Long-Term Adherence and Outcomes. Nutrients. 2024; 16(19):3419. https://doi.org/10.3390/nu16193419}
2. ^{Mount Sinai. Irritable Bowel Syndrome. Accessed October 16, 2024. https://www.mountsinai.org/health-library/diseases-conditions/irritable-bowel-syndrome}