Condition category
Digestive System
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Irritable bowel syndrome (IBS) is a digestive disorder that affects up to 15% of the population. Symptoms include stomach pain, bloating and altered bowel habit. It can be very debilitating and has a great impact on the sufferers quality of life. A diet with an altered amount of carbohydrates (e.g. the types of fruits and vegetables) might prevent symptoms such as bloating, stomach pain and flatulence for many people with IBS. Recent research has shown that the diet described above can impact on the amount of bifidobacteria, a group of bacteria that live in the bowel. Prebiotics can promote (increase) the amount of friendly bifidobacteria in the bowel. This study will investigate the effect of this diet with a prebiotic food supplement on:
1. Bacteria in the bowel and the products of bacterial fermentation
2. Gut symptoms (e.g. wind, bloating)
3. Stool frequency and consistency
4. Changes to urine health markers in relation to the gut bacteria changes
5. Dietary intake
6. Quality of life

Who can participate?
Patients of Guy's and St Thomas' NHS Foundation Trust or Barts and the London NHS Trust aged 18-65 years with IBS and without another major medical condition are eligible for this study

What does the study involve?
Participants are randomly allocated into one of three groups. Those in group 1 are placed on a “sham” diet (one that is not expected to make a difference to the persons IBS symptoms) and are given a placebo pill to take for 4 weeks. Those in group 2 are placed on the treatment diet for 4 weeks and are given a placebo. Those in group 3 are also placed on the treatment diet and take the probiotic for 4 weeks. Each participant visits their study centre three times, once before the study begins, once at one week into the study period and once after the study ends. Participants are assessed according to, for example, what symptoms they experience, their nutrient uptake, quality of life and acceptability of the diet and food supplement.

What are the possible benefits and risks of participating?
There are no anticipated risks to participants; however, changes to dietary intake will be required for a 4-week period. Three stool samples and three urine samples will be collected and symptom, food and quality of life questionnaires will need to be completed. Routine dietary advice will be provided at the end of the study to all patients as per routine clinical care.

Where is the study run from?
King’s College London and The Royal London Hospital (UK)

When is the study starting and how long is it expected to run for?
May 2015 to March 2017

Who is funding the study?
Study funding with research grant from Clasado (UK) ltd and departmental funding from King's College London Nutritional Sciences Division

Who is the main contact?
Bridgette Wilson

Trial website

Contact information



Primary contact

Miss Bridgette Wilson


Contact details

King's College London
4.103 Franklin Wilkins Building
150 Stamford Street
United Kingdom



Additional contact

Dr Kevin Whelan


Contact details

King's College London
4.43 Franklin Wilkins Building
150 Stamford Street
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

The impact of dietary interventions for irritable bowel syndrome on luminal microbiota, symptoms, nutrient intake and quality of life: a randomised controlled trial


Study hypothesis

There is no difference in luminal bifidobacteria concentration between participants after four weeks of a sham diet versus four weeks of a treatment diet with added prebiotic.

Ethics approval

Wales Research Ethics Committee 4, 30/04/2015, ref: 15/WA/0119

Study design

4-week multicentre, single-blind, randomised, three-armed parallel, control trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet


Irritable bowel syndrome


1. 4 week sham diet + placebo
2. 4 week treatment diet + placebo
3. 4 week treatment diet + prebiotic

Intervention type



Drug names

Primary outcome measure

1. Luminal bifidobacteria concentration between groups at 4 weeks
2. Adequate symptom relief between groups at 4 weeks

Secondary outcome measures

1. Difference in IBS symptoms between the three groups at 4-weeks.
2. Difference in stool consistency and stool frequency between three groups at 4-weeks
3. Difference in total and individual luminal gastrointestinal microbiota between the three groups at 4-weeks
4. Difference in faecal short chain fatty acids and pH between the three groups at 4-weeks
5. Differences in urine metabolomics between the three groups at 4-weeks
6. Difference in nutrient intake between dietary interventions at 4-weeks
7. Difference in QOL scores between the three groups at 4-weeks
8. Patient acceptability of the diet and food supplement (questionnaire)

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Men and women aged 18-65 years with diarrhoea-predominant IBS (IBS-D), mixed-type IBS (IBS-M) or unsubtyped IBS (IBS-U) based on Rome III criteria who do not have a major medical condition (diabetes, psychiatric or current eating disorders), gastrointestinal disease (e.g. inflammatory bowel disease, coeliac disease) or history of previous GI surgery, except cholecystectomy and haemorrhoidectomy
2. Individuals able to give informed consent
3. Individuals naive to the dietary intervention

Participant type


Age group




Target number of participants


Total final enrolment


Participant exclusion criteria

1. Females who report to be pregnant or lactating
2. Consumption of antibiotics, prebiotics or probiotics (in food products or as supplements) in the last 4 weeks prior to, or during the study
3. Use of unpermitted medications
4. Participants who have received bowel preparation for investigative procedures in the 4 weeks prior to the study
5. Participants who have had changes to IBS medications or dose in the 4 weeks prior to the study
6. Less than 2 days of at least moderate abdominal pain or discomfort in the screening week
7. Individuals with additional specific dietary needs
8. Individuals with excess alcohol or caffeine intake as assessed by diet questionnaires as these substances may confound symptom results

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Guy's and St Thomas' NHS Foundation Trust
Westminster Bridge Road
United Kingdom

Trial participating centre

Barts and the London NHS Trust
United Kingdom

Sponsor information


King's College London

Sponsor details

1.8 Hodgkin Building
Guy’s Campus
United Kingdom

Sponsor type




Guy's and St Thomas' NHS Foundation Trust

Sponsor details

R&D Department
16th Floor
Tower Wing
Great Maze Pond
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Clasado (UK) Ltd

Alternative name(s)

Funding Body Type

Funding Body Subtype


Funder name

King's College London, Nutritional Sciences Division (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2020 results in (added 07/08/2020)

Publication citations

Additional files

Editorial Notes

07/08/2020: The following changes were made to the trial record: 1. Publication reference added. 2. The total final enrolment was added. 09/09/2016: The recruitment end date has been updated from 24/02/2017 to 09/09/2016. 29/03/2016: Ethics approval information added.