The effect of a low FODMAP diet on luminal microbiota, fermentation and symptoms: A randomised controlled trial
H0: there will be no significant difference in the concentration of faecal bifidobacteria in patients with Irritable Bowel Syndrome (IBS) following a low FODMAP diet (intervention) compared with those following a normal diet (control) for four weeks.
H1: there will be a significant difference in the concentration of faecal bifidobacteria in patients with IBS following a low Fermentable Oligo-, Di-, and Monosaccharides and Polyol (FODMAP) diet (intervention) compared with those following a normal diet (control) for four weeks.
Guy's Research Ethics Committee, 11/11/2009, ref: 09/H0804/89
Randomised controlled parallel group trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Not available in web format, please use contact details below to request a patient information sheet.
Irritable bowel syndrome
4-week low FODMAP diet compared to usual diet.
Patients in the intervention group will receive individualised dietary advice. A low FODMAP diet is a diet low in poorly absorbed fermentable carbohydrates. Patients will follow the diet for 4 weeks. The total duration of the study will be 5 weeks.
Primary outcome measure
To assess the effect of a low FODMAP diet on faecal microbiota in patients with IBS.
Faecal samples will be collected at baseline and at 4 weeks.
Secondary outcome measures
1. To assess the effect of a low FODMAP diet on faecal Short Chain Fatty Acid (SCFA), pH and faecal water in patients with IBS.
2. To assess the effect of a low FODMAP diet on symptoms in patients with IBS.
3. To assess the effect of a low FODMAP diet on stool consistency and frequency in patients with IBS.
4. To assess the nutritional adequacy of a low FODMAP diet in patients with IBS.
5. To assess the acceptability of a low FODMAP diet in IBS patients.
6. Weight and height.
Outcomes will be assessed at baseline and at 4 weeks. Patients will keep a symptom diary and diet diary, and 2 questionnaires will be used to assess nutritional adequacy, FODMAP intake and diet acceptability.
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
Patients will be recruited from Gastrointestinal and Dietetic Outpatient clinics at Guys and St Thomas NHS Foundation Trust, London, UK.
1. Adult patients aged 18-65 years
2. Identified as having IBS based on Rome III criteria
3. Symptoms including bloating and/or diarrhoea
Target number of participants
Participant exclusion criteria
1. Patients with any other gastrointestinal disease or gastrointestinal surgery
2. Patients whose major IBS symptom is constipation
3. Patients receiving lactulose or any other probiotic or prebiotic substances in the four weeks prior to the study
4. Patients who have taken antibiotics in the 4 weeks prior to the study
5. Patients who have received bowel preparation for investigative procedures in the 4 weeks prior to the study
6. Patients with any other significant major organ disorders, including diabetes, psychiatric and current eating disorders
7. Patients who report to be pregnant or lactating
8. Patients who have had changes to IBS medications or dose in the 4 weeks prior to the study
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
4.06 Franklin Wilkins Building
King's College London (UK)
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Basic results (scientific)
2012 results in http://www.ncbi.nlm.nih.gov/pubmed/22739368
Staudacher HM, Lomer MC, Anderson JL, Barrett JS, Muir JG, Irving PM, Whelan K, Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome., J. Nutr., 2012, 142, 8, 1510-1518, doi: 10.3945/jn.112.159285.