The Effect of Gluten in Patients With Irritable Bowel Syndrome and Healthy Volunteers (PROT-IBS)

The Effect of Gluten in Patients With Irritable Bowel Syndrome and Healthy Volunteers: a Randomized, Placebo-controlled Double-blind Cross-over Trial

Patients with Irritable Bowel Syndrome (IBS) often link their symptoms to foods. Interest in dietary management recently increased, including the use of a gluten-free diet. To investigate relation of gluten-free diet (GFD) and IBS, a randomized, double-blind, placebo-controlled cross-over trial will be carried out in adults (>18) and patients with IBS according to Rome IV criteria. The aim is to assess gluten-free versus gluten-containing diet in IBS patients and Healthy Volunteers.

The study is a randomized, double-blind, placebo-controlled, cross-over trial. The aim is to assess the effects of gluten-free diet (GFD) compared to gluten-containing diet (GCD) in IBS patients and Healthy Volunteers on gastrointestinal symptoms, visceral sensitivity, bacterial fermentation, psychological factors and quality of life. The primary hypothesis is that GFD decreases gastrointestinal symptoms compared to GCD and that this change is accompanied with reduced visceral sensitivity and change in bacterial fermentation. The secondary hypothesis is that GFD positively influences psychological factors and quality of life. IBS patients (Rome IV) and Healthy Volunteers are challenged with gluten in this randomized, double-blind, placebo-controlled, cross-over study. They start with GFD or GCD and cross over to the other intervention (both for 14 days). In between there is a wash-out period of at least 14 days. The subjects will get gluten-free meals (lunch and dinner) and have to sprinkle powder over the meals, concealed in sachets with either gluten (vital gluten) or placebo (rice starch). The subjects will follow a strict GFD during the GFD and GCD periods. The subjects will eat and drink as before the study during the washout period. Primary outcomes are change in gastrointestinal symptoms, assessed by questionnaires, including IBS Severity Scoring System (IBS-SSS) and Gastrointestinal Symtom Rating Scale-IBS (GSRS-IBS). A 50-point reduction in IBS-SSS indicates clinical response. Bacterial fermentation (exhaled hydrogen and methane) and visceral sensitivity will be measured using the Lactulose-Nutrient Challenge Test. Secondary outcomes are change in psychological factors and quality of life assessed by questionnaires, including CSI, HADS, HSPS, IBSQOL, PHQ-15 and VSI.

The randomization was done by employees of the hospital that were otherwise not involved in the study by drawing concealed envelops. The interventions were concealed plastic bags marked A or B.

The subjects will sprinkle gluten powder over their meals, twice a day. (14 g/day vital gluten: Real Foods, Edinburgh, United Kingdom). Plastic sachet marked with B (WePack, Derbyshire, United Kingdom). Free of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs).

The subjects will sprinkle placebo powder over their meals, twice a day. (14 g/day rice starch: Doves Farm Foods Ltd., Berkshire, United Kingdom) Plastic sachets marked with A (WePack, Derbyshire, United Kingdom). Low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs).

Irritable Bowel Syndrome-Severity Scoring System (IBS-SSS) is a validated questionnaire that incorporates typical IBS symptoms such as abdominal pain, abdominal distension and bowel dysfunction, as well as quality of life. Subjects rated their symptoms on a visual analogue scale. The maximum achievable score is 500 points (sum of the 5 scales). A reduction in the total IBS-SSS score of at least 50 points is considered to indicate a clinically significant improvement in symptoms. The scale can also be used to classify IBS symptoms severity: <75 points (no symptoms), 75-175 points (mild symptoms), 175-300 points (moderate symptoms) and >300 points (severe symptoms). Measured after both dietary periods and at baseline of both periods.

Change in Gastrointestinal Symptom Rating Scale - Irritable Bowel Syndrome (GSRS-IBS) measures symptom severity and symptom frequency in IBS patients and is a reliable and validated questionnaire. Thirteen questions are evaluated and rated from 1 (no discomfort at all) to 7 (very severe discomfort) on a Likert scale. The total scores can range from 13 to 91 (sum of the domains). The GSRS-IBS evaluates 5 domains: abdominal pain, bloating, constipation, diarrhea and satiety. Measured after both dietary periods and at baseline of both periods.

The Central Sensitization Inventory (CSI) measures central sensitization related symptoms with 25 questions with a maximum score of 100. A high score indicates high likelihood of central sensitization. Measured after both dietary periods and at baseline of both periods.

The Hospital Anxiety and Depression Scale (HADS) contains 7 items for depression and 7 for anxiety. Each item is scored from 0 to 3, and therefore the total score per subscale can range from 0 to 21. When subjects score >10 on 1 or 2 of the subscales, clinically significant psychological distress (anxiety or depression) is likely present. Measured after both dietary periods and at baseline of both periods.

The Highly Sensitive Person Scale (HSPS) contains 27 items and is a valid and reliable questionnaire that measures sensory-processing sensitivity in individuals. Each item is scored from 1 to 7, and therefore the total score can range from 27 to 189. Higher scores indicate high sensory-processing sensitivity. Measured after both dietary periods and at baseline of both periods.

The Irritable Bowel Syndrome Quality of Life Questionnaire (IBSQOL) is a 30-item questionnaire that measures quality of life specific to IBS. The IBSQOL is validated and can be used to assess the impact of IBS and possible treatment interventions on quality of life. The following domains are measured: emotional health, mental health, energy, sleep, food/diet, social role, physical functioning, physical role and sexual relations. Scores range from 0 to 100% per domain. Higher scores indicate that IBS influences quality of life greater. Measured after both dietary periods and at baseline of both periods.

The (PHQ-15) is a validated questionnaire that evaluates 15 somatic symptoms and can be used as a screening tool for somatization in clinical research. The maximum score for men is 28 and 30 for women due to a question about menstrual problems. Measured after both dietary periods and at baseline of both periods.

The Visceral Sensitivity Index (VSI) is a validated and reliable psychometric instrument which assesses gastrointestinal symptom-specific anxiety. The VSI contains 15 items that are scored from 0 to 5, therefore the total score can range from 0 to 75. Higher scores indicate more severe gastrointestinal symptom-specific anxiety. Measured after both dietary periods and at baseline of both periods.

Frozen serum samples will be analyzed in the future by immunological testing (e.g. ELISA-kit, assays). The future analyses will include interleukins 6 and 8 (IL-6,8) as well as tumor necrosis factor-alpha (TNF-alpha) and immunological markers such as lipopolysaccharide-binding protein (LBP), sCD14, anti-gliadin antibodies (AGA), fibroblast growth factors, fatty acid-binding protein 2, anti-flagellin immunoglobulin G (IgG) and endotoxin-core antibodies immunoglobulin M (IgM). Analyses will be done on samples from before and after both dietary periods.

Frozen urine samples will be analyzed in the future by metabolome analysis and urine mass spectrometry. For example the metabolites p-hydroxybenzoic acid, histamine and azelaic acid will be measured. Analyses of samples from before and after both dietary periods. Analyses will be done on samples from before and after both dietary periods.

Fecal microbiota analysis using 16 S RNA technique and Dysbiosis Test. Analyses will be done on samples from before and after both dietary periods.

Inclusion Criteria: Adult patients with IBS according to Rome IV criteria Exclusion Criteria: allergy or documented intolerance to food, severe cardiovascular, hepatic, neurological or psychiatric disease serious gastrointestinal disease: including celiac disease and inflammatory bowel diseases (IBD), diabetes bowel dysfunction related to previous surgery pregnant or lactating women usage of antibiotics within 4 weeks before inclusion strict avoidance of foods

Algera JP, Magnusson MK, Ohman L, Storsrud S, Simren M, Tornblom H. Randomised controlled trial: effects of gluten-free diet on symptoms and the gut microenvironment in irritable bowel syndrome. Aliment Pharmacol Ther. 2022 Nov;56(9):1318-1327. doi: 10.1111/apt.17239. Epub 2022 Sep 29.