Effects of Dietary Fibre in Irritable Bowel Syndrome (IBS)
Effects of Dietary Fibre in Irritable Bowel Syndrome (IBS)
The aim of the study is to investigate how different dietary fibre combinations affects
 physiological and microbiological outcomes, in addition to symptoms in those with IBS. The
 study will also explore the differences in responses between different fibres in different
 sub-types of IBS (e.g. constipation-predominant, diarrhoea-predominant and mixed).
Currently, national and international guidelines are based upon trials of dietary fibre in
 IBS symptoms that report opposing effects. For this reason, recommendations regarding dietary
 fibre food supplementation in IBS are often conflicting. Indeed, the confusion surrounding
 dietary fibre recommendations in IBS is a consequence of the limited understanding of the
 different types of dietary fibres used, their physiology and their functions in different
 sub-groups of IBS.

 Different fibres have different characteristics (e.g. solubility, viscosity and
 fermentability) which drive different functionalities (stool forming, fermentation) in the
 gastrointestinal tract, yet it is currently unknown whether administration of dietary fibre
 combinations will result in symptomatic improvement in people with IBS.

 Participants will be randomised to one of three parallel arms for a duration of 8 weeks.

 The study will consist of 4 visits in total. The first visit will involve taking consent and
 assessing eligibility. Participants will complete the Rome IV diagnostic criteria as part of
 their eligibility assessment. Participants will be asked to complete a food and symptom diary
 for the next 7 days. Diary data will be used to confirm frequency and severity of IBS
 symptoms and ensure there is no discrepancy between participant report on the Rome IV
 diagnostic criteria.

 Visit 2: Baseline (approx 1.5 hours). Height and weight will be recorded. Participants will
 complete 7 questionnaires, provide a stool sample, a blood sample and will ingest the
 SmartPill (wireless motility capsule). Participants will blinded to the intervention and will
 be provided with sachets containing either fibre 1 (combined fibres), fibre 2 (natural
 fibres) or placebo to consume over an 8-week period.

 Visit 3: Mid-point (approx 1 hour). Participants will complete 5 questionnaires and provide a
 stool sample.

 Visit 4: Endpoint (approx 1.5 hours). Height and weight will be recorded. Participants will
 complete 7 questionnaires, provide a stool sample, a blood sample and will ingest the
 SmartPill (wireless motility capsule).
Inclusion Criteria:

 -  Interested in taking part

 -  Ability to give informed consent

 -  Men and women aged 18-65 years with diarrhoea-predominant IBS (IBS-D),
 constipation-dominant IBS (IBS-C), or mixed (IBS-M), based on fulfilment of the Rome
 IV criteria for irritable bowel syndrome who do not have a major medical condition
 (e.g. diabetes, psychiatric or current eating disorders), severe oesophagitis,
 gastritis or duodenitis, gastrointestinal disease (inflammatory bowel disease, coeliac
 disease, active diverticulitis), or history of previous GI surgery (excluding
 appendicectomy, cholecystectomy and haemorrhoidectomy), severe renal, cardiac,
 pulmonary, or other chronic diseases likely to affect motility, history of gastric
 bezoars.

 Exclusion Criteria:

 -  Females who report to be pregnant or lactating

 -  Body Mass Index (BMI) >40 kg/m2

 -  Use of unpermitted medications in the last 4 weeks prior to, or during the study
 including: Antibiotics within the last 4weeks, dietary fibre food supplements within
 the last 4 weeks (e.g. Fybogel, Lactulose), prebiotics or probiotics (in food products
 or as supplements) within the last 4 weeks, other dietary supplements that may affect
 the luminal microenvironment of the intestine (e.g. Orlistat)

 -  Use of drugs known to alter GI motility, transit or gastric pH (e.g. mebeverine,
 opiates, monoamine oxidase inhibitors, phenothiazines) in the last 1 week

 -  Full bowel preparation for a diagnostic procedure within the last 4 weeks

 -  Changes to IBS medications or dose in the 4 weeks prior to the study

 -  Changes to anti-depressant medications or dose in the 12 weeks prior to the study

 -  Swallowing disorders (physical or psychological)

 -  Use of implantable and/or medical devices such as pacemakers

 -  Individuals following extreme diets e.g. 8 or more caffeinated serves per day, 4 or
 more bottles of wine (40 or more units of alcohol per week) or equivalent per week as
 assessed by diet questionnaires or changes to smoking habits

 -  Individuals who have participated in other intervention trials within 3 months prior
 to screening

 -  Allergies to components (soy) of the SmartBar (required for SmartPill protocol)

 -  Abdominal pain for less than 2 days in the screening week (based on the GSRS mild to
 severe)

 -  Those who report adequate relief of symptoms at baseline using the GSQ