Randomised Clinical Trial

Yoga vs a Low-FODMAP Diet in Patients With Irritable Bowel Syndrome

D. Schumann; J. Langhorst; G. Dobos; H. Cramer


Aliment Pharmacol Ther. 2018;47(2):203-211. 

In This Article


Study Design and Drop-out Rate

This single-blind randomised controlled trial was conducted in the Department of Internal and Integrative Medicine, at the Kliniken Essen-Mitte; based in the Faculty of Medicine at the University of Duisburg-Essen in Essen, Germany. The study was approved by the University of Duisburg-Essen's Ethics Committee (Approval No: 15–6653-BO), and registered on the website ClinicalTrials.gov (Registration No: NCT02721836), prior to patient recruitment. The study was conducted and reported in line with the consolidated standards of reporting trials (2010) guidelines.[20]


Patients were recruited by the Department of Internal and Integrative Medicine via advertisements online and in the local press in March and April 2016. Individuals who responded were screened by a research assistant to assess their eligibility. Those who appeared to be eligible were invited for an assessment conducted by a study physician. Stool analysis was used to determine the presence or absence of faecal lactoferrin as a marker of intestinal inflammation. Individuals who met the study inclusion criteria, and did not meet its exclusion criteria, were included in the trial. Participants received detailed oral and written information about the study. Those who wished to proceed signed a consent form to demonstrate their informed consent.

Male and female patients were included if they were between 18 and 75 years old, had suffered from diagnosed IBS for at least 6 months and met the 'Rome-III' criteria. No restrictions were placed on the IBS-type. To participate, patients had also to be physically and mentally capable of performing yoga exercises. The study exclusion criteria included a concentration of faecal lactoferrin > 7 mg/g, the presence of inflammatory bowel disease, complete resection of the colon, ongoing acute infection, concurrent disease that precluded even light yoga exercise, pregnancy and regular yoga practice or nutrition counselling in the previous 12 months.


Patients were randomly assigned 1:1 to yoga or nutrition counselling by block-randomisation with randomly varying block lengths, stratified by a history or nonhistory of diagnosed depression. The randomisation list was created by a biometrician, not involved in the study's patient recruitment or assessment, using the Random allocation software.[21] The list was password-secured and accessible only by the biometrician concerned. The latter prepared sealed, sequentially numbered, opaque envelopes containing the treatment assignments, based on this list. After the study's baseline assessments had been conducted, and written consent information had been obtained, the physician opened the lowest-numbered envelope to reveal each patient's assignment.


Yoga. The yoga intervention included traditional hatha yoga group sessions of 75 minutes duration twice weekly for a period of 12 weeks. The yoga intervention was designed by a certified hatha yoga instructor, prior to the intervention, and was specifically customised for patients with IBS. Those yoga postures and breathing techniques thought to relax the body and mind, as well as asana (poses) traditionally thought to influence the digestive organs positively, were included (see supporting information).[11] The study's yoga intervention was provided by the same yoga instructor throughout. She guided patients to focus on their bodies, during their yoga classes, taking a nonjudgmental attitude towards their bodily sensations. One of the weekly classes consisted of yoga postures and yogic breathing techniques.[11] The second explored yoga philosophy[22] and yogic meditation techniques, including mantra meditation and yoga nidra (deep relaxation techniques).[23] The postures used in each class built upon the previous ones, with the difficulty and intensity levels being increased carefully as the program progressed (Table S1). Patients were provided with a written manual and three half-hour videos and were encouraged to practice their yoga at home every day. Prior to patients' home practice, yoga practice was introduced in class. The patients indicated their daily home practice time (in minutes) in a daily log.

Low-FODMAP diet. Patients who were randomised to the nutrition group received 4 sessions of nutritional counselling; consisting of an educational group lecture, 2 sessions of individual counselling based around a food diary and a group counselling session. Each of these sessions lasted 60–90 minutes. Patients in this study arm also received a pamphlet containing nutritional advice for people with irritable bowel syndrome, produced by the german association for nutrition (DGE).[24] This pamphlet explained the nature of a low-FODMAP diet and the principles of balanced nutrition. Specifically, patients were instructed that foods rich in fructans and galacto-oligosaccharides (eg, wheat, rye, garlic, onions and legumes), items that contained lactose, foods with fructose in excess of glucose (such as apples, mangoes and honey), as well as food sources rich in sorbitol, mannitol, maltitol and xylitol (such as apricots, peaches and artificially sweetened products) must be avoided.[25] To aid patients in their food choices, they were also given a set of low-FODMAP recipes, a list of foods to avoid and another of foods that they might eat instead. After the study's 12-week intervention period (elimination phase), patients re-challenged each week a different FODMAP group for 2 to 3 days during that week to test individual tolerance levels to each of the FODMAP groups (reintroduction phase). This scheme was explained to the patients in an individual counselling session. All patients completed a 6-day food diary on two occasions; once during the study screening period and a second time during the last week of the 12-week study intervention period. These diaries were scored by a nutritionist according to the amount of FODMAP consumption. Patients' compliance with the nutritional advice given was rated by the same nutritionist. It was also self-rated by each patient. In both cases, a nonvalidated 100 mm visual analogue scale (VAS), with '0' indicating no compliance at all and '100' indicating complete compliance, was used.

Outcome Assessment

The study's outcomes were assessed at weeks 12 and 24, after randomisation by an outcome assessor 'blinded' to patients' group allocation.

Primary outcome. The irritable bowel syndrome severity scoring system (IBS-SSS) is a self-reported questionnaire exploring the severity and frequency of patients' pain, the degree of abdominal distension/bloating experienced, the level of patients' satisfaction with their bowel habits and the extent to which the latter interfere with patients' everyday lives.[26] Each question is scored from 0–100 on a visual analogue scale. This study used patients' gastrointestinal symptoms, as assessed by the IBS-SSS at week 12, as its primary outcome measure. All other outcomes were defined as secondary outcomes and were analysed exploratively only. This way, no a-level adjustment was necessary to maintain the overall Type I error rate of 5%.[27]

The maximum achievable IBS-SSS score is 500; with higher scores indicating higher symptom severity. Mild, moderate and severe cases are indicated by scores of 75–175, 175–300 and > 300 respectively. Patients with a score below 75 are considered to be in remission, as healthy controls scored within this range. Clinically relevant improvements are defined as a decrease of 50 points or more.[26]

Secondary outcomes. This study used the irritable bowel syndrome quality of life (IBS-QOL) measure[28] to assess specific aspects of participants' quality of life related to their IBS and the 36-Item short form health survey (SF-36)[29] to capture their more general health-related quality of life. Symptoms of anxiety or depression were monitored by the hospital anxiety and depression scale (HADS).[30] Perceived Stress was assessed by using the cohen perceived stress scale (CPSS)[31] and the perceived stress questionnaire (PSQ).[32] While the CPSS is the tool most often used to assess stress in general, the PSQ is most frequently used in patients with gastrointestinal and/or psychosomatic disorders. Additional data about study participants' body awareness and responses were gathered using the body awareness questionnaire (BAQ)[33] and body responsiveness scale (BRS)[34] respectively. Finally, patients kept diaries, which contained questions asking about the extent to which they experienced adequate relief (AR) of their IBS symptoms and/or a general global improvement. Patients' gut microbiomes were also assessed, but these results will be reported elsewhere.


Patients were asked to record any adverse events that they had experienced during the study period, regardless of their potential relationship to the study intervention. Patients that experienced such events were asked to see the study physician to assess the events' import and to initiate a response if needed. Additional open-ended questions were used, following the study interventions, to capture any adverse events not previously reported by patients.

Sample Size Calculation and Statistical Analysis

The required sample size was calculated a priori. A group difference of 83 points on the IBS-SSS total score has been shown to represent a considerable self-reported improvement.[26] Assuming a standard deviation of 103.8, based on a former trial with IBS patients,[35] a two-sided, level 5% t test requires a total of 26 patients per study group in order to detect a respective group difference with a statistical power of 80%. To account for the potential loss of statistical power from the withdrawal of up to 10% of participants, the trial aimed to recruit a total of at least 58 patients. All of the trial analyses were based on an intention-to-treat basis, with all participants being randomised, regardless of whether or not they provided a full set of data or adhered to the study protocol. Missing data were multiply imputed using the Markov chain Monte Carlo Method,[36,37] yielding a total of 50 complete data sets. Baseline group differences in patients' sociodemographic and clinical characteristics were analysed using Student's t tests for continuous data and chi-square tests for categorical data. Linear outcomes were analysed by univariate analyses of covariance, which modelled the outcomes at weeks 12 or 24 to produce overall effect size estimates, 95% confidence intervals and P-values. In order to assess the interventions' safety, the number of patients in each study group that experienced serious or nonserious adverse events during the study period was assessed, using chi-square tests. In keeping with the work of Francis et al, the findings' clinical relevance was assessed by comparing the number of participants who reported an improvement of 50 or more points on their IBS-SSS total scores[26] at weeks 12 and 24, using chi-square tests. Finally, the number of participants in clinical remission, based on an IBS-SSS total score < 75, was compared between groups at weeks 12 and 24 using chi-square tests.

Explorative statistical subgroup analyses were performed to control for potential differences in the effectiveness of the interventions for patients with single IBS subtypes.

All analyses were performed using the statistical package for social sciences software (IBM spss Statistics for Windows, release 22.0. Armonk, NY, USA: IBM Group).