Effect of a Low FODMAP Diet in IBS and Functional Constipation with Bloating: a Randomized Double-Blind Trial

NCT06871748 | Not Yet Recruiting

• 1 other identifier: Si 148/2025
• Study Type: interventional
• Target: 34
• Locations: 0 countries
• Sites: N/A

Brief Summary

This clinical study aims to evaluate the effects of a low FODMAP diet compared to a high FODMAP diet in patients with Irritable Bowel Syndrome (IBS) and Functional Constipation (FC) with predominant bloating. The study is a randomized, double-blind, controlled trial designed to assess whether a diet low in fermentable carbohydrates can improve bloating symptoms, gut microbiota composition, intestinal gas production, and metabolic outputs. Patients meeting the Rome IV criteria for IBS or FC with persistent bloating will be enrolled and randomly assigned to receive either a low or high FODMAP diet for two weeks. Meals will be standardized to control FODMAPs composition, ensuring that FODMAP content is the primary variable. The primary endpoint is the proportion of participants with a ≥30% reduction in bloating severity, measured using the Visual Analog Scale (VAS). Secondary outcomes include changes in global IBS symptoms, abdominal pain, bowel movements, stool consistency, microbiota diversity, hydrogen/methane gas production, and metabolomic profiles. This study will contribute to the growing body of evidence supporting dietary management in disorders of gut-brain interaction (DGBI), particularly in bloating-predominant IBS and FC, and will provide insights into the mechanisms linking diet, gut microbiota, and symptom improvement.

Conditions

Irritable Bowel Syndrome (IBS); Constipation - Functional; Bloating

Keywords

Irritable Bowel Syndrome (IBS); Functional Constipation; FODMAP; Microbiota

Outcome Measures

Primary Outcomes (1)

• Change in Bloating Severity (VAS)

  The primary outcome is the change in bloating severity, measured using the Visual Analog Scale (VAS). The VAS score ranges from 0 (no bloating) to 10 (severe bloating), with higher scores indicating worse bloating symptoms. Participants will record daily bloating scores throughout the intervention period. The proportion of participants achieving a ≥30% decrease in bloating severity from baseline will be analyzed.

  Baseline to 2 weeks (End of Intervention)

Secondary Outcomes (15)

• Reduction in Global IBS Symptoms (IBS-SSS)

  Baseline to 2 weeks

• Change in Abdominal Pain (VAS)

  Baseline to 2 weeks

• Change in Stool Frequency and Consistency

  Baseline to 2 weeks

• Changes in Gut Microbiota Composition

  Baseline to 2 weeks

• Change in Hydrogen Gas Production (Lactulose Breath Test)

  Baseline to 2 weeks

Study Arms (2)

Low FODMAP Diet

EXPERIMENTAL

Participants will follow a low FODMAP diet for two weeks, consuming standardized meals with minimal fermentable carbohydrates. Meals match the high FODMAP diet in appearance to maintain blinding.

Other: Low FODMAP Diet

High FODMAP Diet

ACTIVE COMPARATOR

Participants will follow a high FODMAP diet for two weeks, consuming standardized meals with high fermentable carbohydrates. Meals match the low FODMAP diet in appearance to maintain blinding.

Other: High FODMAP Diet

Interventions

Low FODMAP Diet OTHER

A standardized diet containing low levels of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), designed to reduce bloating and gastrointestinal symptoms. Meals are pre-prepared, calorie-matched, and visually identical to those in the high FODMAP group to maintain blinding. Participants will consume three main meals and one snack daily for two weeks, with adherence monitored through food diaries and photos.

Low FODMAP Diet

High FODMAP Diet OTHER

A standardized diet containing high levels of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) to assess its impact on bloating and gastrointestinal symptoms. Meals are calorie-matched and visually identical to those in the low FODMAP group to maintain blinding. Participants will consume three main meals and one snack daily for two weeks, with adherence tracked through food diaries and photos.

High FODMAP Diet

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age ≥18 years
• Diagnosed with Irritable Bowel Syndrome (IBS) or Functional Constipation (FC) based on Rome IV criteria
• Persistent bloating affecting daily life, with a bloating VAS score ≥4
• Stable bowel habits with Bristol Stool Form Scale (BSFS) type 3-5
• History of prior treatment with antispasmodics and/or prokinetics (allowed if dose remains stable)
• Able to comply with dietary intervention and study procedures

You may not qualify if:

• Prior gastrointestinal surgery (except appendectomy or cholecystectomy)
• Use of antibiotics, proton pump inhibitors (PPIs), probiotics, NSAIDs, lactulose, or metformin within the past 4 weeks
• Presence of systemic diseases affecting gut microbiota (e.g., liver cirrhosis, uncontrolled diabetes, end-stage renal disease, obesity, cancer, psychiatric disorders)
• Inability to consume study meals or follow dietary restrictions

Sponsors & Collaborators

• Mahidol University: lead

Related Publications (5)

• Drossman DA, Tack J. Rome Foundation Clinical Diagnostic Criteria for Disorders of Gut-Brain Interaction. Gastroenterology. 2022 Mar;162(3):675-679. doi: 10.1053/j.gastro.2021.11.019. Epub 2021 Nov 19. No abstract available.

  PMID: 34808139 BACKGROUND

• Camilleri M. Diagnosis and Treatment of Irritable Bowel Syndrome: A Review. JAMA. 2021 Mar 2;325(9):865-877. doi: 10.1001/jama.2020.22532.

  PMID: 33651094 BACKGROUND

• Andrews CN, Sidani S, Marshall JK. Clinical Management of the Microbiome in Irritable Bowel Syndrome. J Can Assoc Gastroenterol. 2020 Jan 4;4(1):36-43. doi: 10.1093/jcag/gwz037. eCollection 2021 Feb.

  PMID: 33644675 BACKGROUND

• Varney J, Barrett J, Scarlata K, Catsos P, Gibson PR, Muir JG. FODMAPs: food composition, defining cutoff values and international application. J Gastroenterol Hepatol. 2017 Mar;32 Suppl 1:53-61. doi: 10.1111/jgh.13698.

  PMID: 28244665 BACKGROUND

• Muir JG, Shepherd SJ, Rosella O, Rose R, Barrett JS, Gibson PR. Fructan and free fructose content of common Australian vegetables and fruit. J Agric Food Chem. 2007 Aug 8;55(16):6619-27. doi: 10.1021/jf070623x. Epub 2007 Jul 11.

  PMID: 17625872 BACKGROUND

MeSH Terms

Conditions

Irritable Bowel Syndrome

Interventions

FODMAP Diet

Condition Hierarchy (Ancestors)

Colonic Diseases, Functional; Colonic Diseases; Intestinal Diseases; Gastrointestinal Diseases; Digestive System Diseases

Intervention Hierarchy (Ancestors)

Elimination Diets; Diet; Nutritional Physiological Phenomena; Diet, Food, and Nutrition; Physiological Phenomena

Study Officials

• Monthira Maneerattanaporn, MD

  Mahidol University Faculty of Medicine Siriraj Hospital

  STUDY DIRECTOR

• Tanawat Geeratragool, MD

  Mahidol University Faculty of Medicine Siriraj Hospital

  PRINCIPAL INVESTIGATOR

• Somchai Leelakusolvong, MD

  Mahidol University Faculty of Medicine Siriraj Hospital

  STUDY CHAIR

Central Study Contacts

Monthira Maneerattanaporn, MD

CONTACT

662419777; monthira.man@mahidol.ac.th

Tanawat Geeratragool, MD

CONTACT

66823430096; tanawat.grtg@gmail.com

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: This study employs a double-blind design, where both participants and study personnel (including investigators, dietitians, and outcome assessors) are blinded to dietary assignments. Meals in both groups are designed to have identical appearance, texture, and calorie content, differing only in FODMAP composition to maintain blinding. Food preparation staff, who are not involved in data collection or patient interaction, will be the only personnel aware of group assignments. The randomization sequence is generated by an independent researcher who does not participate in data analysis or outcome assessment. Blinded data analysis will be conducted to prevent bias. Participants will be instructed not to discuss meal characteristics to preserve masking. This ensures objective assessment of dietary effects on bloating, microbiota composition, gas production, and metabolic profiles.
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Associate Professor

Model Details: This study is a randomized, double-blind, controlled trial investigating the effects of a low FODMAP diet compared to a high FODMAP diet in IBS and functional constipation patients with bloating. Participants will be randomly assigned to one of two dietary intervention groups for two weeks. The trial employs block randomization (block size=4). Both participants and study personnel will be blinded to the diet assignment, with identical meal appearances to maintain blinding. Outcomes include clinical symptom improvement, gut microbiota changes, gas production, and metabolomic profiles. Data will be analyzed using chi-square tests, logistic regression, and microbiome diversity metrics. This study aims to provide mechanistic insights and evidence-based dietary recommendations for managing bloating-predominant IBS and functional constipation.

Study Record Dates

• First Submitted: February 28, 2025
• First Posted: March 12, 2025
• Study Start: March 15, 2025
• Primary Completion: March 15, 2026
• Study Completion (Estimated): July 31, 2026
• Last Updated: March 12, 2025

Record last verified: 2025-02

Data Sharing

• IPD Sharing: Will not share