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

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 quality of life. A diet with an altered amount of carbohydrates (e.g. the types of fruits and vegetables) might be effective for 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 in the bowel. Probiotics are ‘friendly’ bacteria added to foods that can increase the amount of bifidobacteria in the bowel. This study will investigate the effect of this diet with a probiotic 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. Dietary intake
5. Quality of life
The effect of dietary change on symptoms and the bacteria in the bowel in the longer term will also be studied.

Who can participate?
Patients of Guy's and St Thomas' NHS Foundation Trust or St George's Healthcare Trust aged 18-65 with IBS

What does the study involve?
The study incorporates three study centre visits, one before the 4-week study period, one after the 4-week study period and one visit at 12 months. There may also need to be one initial visit prior to the baseline visit in order to obtain consent if the patient is not identified in clinic, but screened from the referral letter.

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. Two stool 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?
The study will be run from King’'s College London and St George’'s Healthcare Trust

When is the study starting and how long is it expected to run for?
Recruitment will continue until September 2014

Who is funding the study?
National Institute for Health Research (NIHR) (UK)

Who is the main contact?
Heidi Staudacher, Research Dietitian

Trial website

Contact information



Primary contact

Ms Heidi Staudacher


Contact details

King's College London
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

Current study hypothesis as of 24/01/2013:
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 probiotic.

Previous study hypothesis until 24/01/2013:
There is no difference in luminal bifidobacteria concentration between participants after four weeks of a sham diet versus four weeks of a fermentable carbohydrate restriction with added probiotic.

Ethics approval

NRES Committee London-Fulham, 08/10/2012, ethics no. 12/LO/1402

Study design

2 x 2 factorial design randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Irritable bowel syndrome


Current interventions as of 24/01/2013:
4-week treatment diet + placebo
4-week treatment diet + added probiotic
4-week week sham diet + placebo
4-week sham diet + added probiotic

Previous interventions until 24/01/2013:
4-week fermentable carbohydrate restriction + placebo
4-week fermentable carbohydrate restriction + added probiotic
4-week week sham diet + placebo
4-week sham diet + added probiotic

Intervention type



Drug names

Primary outcome measure

1. Luminal bifidobacteria concentration between groups at 4 weeks

Added 05/08/2014:
2. Proportion of participants with adequate relief of IBS symptoms at 4 weeks

Secondary outcome measures

1. Difference in total and individual luminal gastrointestinal microbiota at 4 weeks
2. Difference in faecal short chain fatty acids and pH between groups at 4 weeks
3. Difference in IBS symptoms between groups at 4 weeks
4. Difference in stool consistency between groups at 4 weeks
5. Difference in nutrient intake between groups at 4 weeks
6. Difference in quality of life (QOL) scores between groups at 4 weeks

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 IBS-D, IBS-M or unsubtyped IBS based on Rome III criteria who do not have a major medical condition (diabetes, psychiatric or current eating disorders)
2. Gastrointestinal disease (e.g. inflammatory bowel disease, coeliac disease)
3. History of previous GI surgery, except cholecystectomy and haemorrhoidectomy

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Females who report to be pregnant or lactating
2. Consumption of antibiotics, pre or probiotics (in food products or as supplements) in the last 4 weeks prior to, or during the study
3. Use of unpermitted medications (e.g. biological therapies)
4. Patients who have received bowel preparation for investigative procedures in the 4 weeks prior to the study
5. Patients who have had changes to IBS medications or dose in the 4 weeks prior to the study
6. Abdominal pain or discomfort for less than 2 days in the screening week, the frequency threshold recommended for clinical trials. Exclusion of those with minimal symptoms is recommended, and only those that experience pain on at least two days will be included.
7. Individuals with additional specific dietary needs

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

King's College London
United Kingdom

Sponsor information


King's College London (UK)

Sponsor details

Diabetes and Nutritional Sciences
Franklin Wilkins Building
150 Stamford Street
United Kingdom

Sponsor type




Funder type


Funder name

National Institute for Health Research

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government


United Kingdom

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)

Publication list

2017 results in:
2017 results in:

Publication citations

Additional files

Editorial Notes

19/10/2017: Publication reference added. 11/10/2017: Publication reference added. 05/08/2014: The funder was changed from King's College London to National Institute for Health Research (NIHR) (UK). 05/08/2014: The target number of participants was changed from 93 to 100. 17/07/2013: The overall trial end date was changed from 01/08/2014 to 30/09/2014.