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

NCT ID: NCT06871748

Last Updated: 2025-03-12

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 34 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-03-15
• Study Completion Date: 2026-07-31

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.

Detailed Description

Irritable Bowel Syndrome (IBS) and Functional Constipation (FC) are chronic Disorders of Gut-Brain Interaction (DGBI) characterized by altered motility, visceral hypersensitivity, dysbiosis, and central nervous system processing abnormalities. Bloating is a challenging and distressing symptom that often persists despite standard pharmacological treatments.

The low FODMAP diet has been widely studied as a dietary approach to alleviate IBS symptoms. FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are poorly absorbed short-chain carbohydrates that increase osmolarity, promote intestinal gas production, and alter gut microbiota, leading to bloating and discomfort. Although studies support the effectiveness of the low FODMAP diet, existing research lacks controlled, blinded trials assessing its impact on bloating-specific symptoms and related physiological markers.

This study addresses these gaps by using a double-blind, controlled design with rigorously standardized meals containing well-defined FODMAP content. It will assess clinical outcomes, gut microbiota composition, gas production, and metabolomic changes to elucidate the mechanisms underlying the diet's effects.

Study Design This is a randomized, double-blind, controlled trial conducted at a single center. Participants will be assigned to receive either a low FODMAP or a high FODMAP diet for two weeks.

Participants:

Adults ≥18 years diagnosed with IBS or FC with persistent bloating based on Rome IV criteria.

Intervention:

Standardized meal plans containing either low FODMAP or high FODMAP content.

Randomization:

Computer-generated block randomization (block of 4)

Blinding:

Investigators, study staff, and participants will remain blinded to the dietary allocation.

Primary Outcome:

≥30% reduction in bloating severity on the VAS scale.

Secondary Outcomes:

Changes in global IBS symptoms (IBS-SSS) or constipation symptoms (PAC-Sym) Abdominal pain (VAS) stool frequency, and consistency (Bristol Stool Form Scale). Gut microbiota diversity and composition (16S rRNA sequencing). Intestinal gas production (hydrogen/methane breath test). Metabolomic analysis (short-chain fatty acids, urine histamine, azelaic acid). Use of rescue medications for symptom relief.

Study Procedures

Baseline Assessment:

Demographic data, medical history, and dietary habits (7-day food diary). Baseline bloating severity, stool consistency, and quality of life (IBS-QoL, PAC-QoL).

Microbiota, breath test, and metabolomic sampling.

Intervention Phase (2 Weeks):

Participants consume standardized low or high FODMAP meals (3 main meals + 1 snack/day).

Daily recording of symptoms, bowel movements, and use of rescue medications.

Follow-up Assessments:

Week 1: Phone follow-up to assess adherence and symptom progression. Week 2: Final clinical and laboratory assessments (identical to baseline). Data collection for statistical analysis comparing treatment effects.

Statistical Analysis Primary endpoint (bloating reduction) analyzed using Chi-square/Fisher's exact test.

Secondary outcomes analyzed with paired t-tests, Mann-Whitney U tests, and logistic regression.

Microbiota diversity assessed using Shannon index, beta diversity, and PERMANOVA testing.

Significance and Impact This study will provide high-quality evidence on the effectiveness of the low FODMAP diet for bloating-predominant IBS and FC, addressing critical knowledge gaps. By integrating clinical, microbiota, and metabolomic data, it will enhance understanding of diet-microbiota interactions and their role in symptom modulation.

Conditions

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

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: TREATMENT
• Blinding Strategy: QUADRUPLE

Study Groups

Low FODMAP Diet

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.

Group Type: EXPERIMENTAL

Low FODMAP Diet

Intervention Type: 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.

High FODMAP Diet

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.

Group Type: ACTIVE_COMPARATOR

High FODMAP Diet

Intervention Type: 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.

Interventions

Low FODMAP Diet

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.

Intervention Type: OTHER

High FODMAP Diet

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.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• 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

Exclusion Criteria

• 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

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Mahidol University

OTHER

Sponsor Role: lead

Responsible Party

Watcharasak Chotiyaputta

Associate Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Monthira Maneerattanaporn, MD

Role: STUDY_DIRECTOR

Mahidol University Faculty of Medicine Siriraj Hospital

Tanawat Geeratragool, MD

Role: PRINCIPAL_INVESTIGATOR

Mahidol University Faculty of Medicine Siriraj Hospital

Somchai Leelakusolvong, MD

Role: STUDY_CHAIR

Mahidol University Faculty of Medicine Siriraj Hospital

Central Contacts

Monthira Maneerattanaporn, MD

Role: CONTACT

monthira.man@mahidol.ac.th

662419777

Tanawat Geeratragool, MD

Role: CONTACT

tanawat.grtg@gmail.com

66823430096

References

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.

Reference Type: BACKGROUND

PMID: 34808139 (View on PubMed)

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.

Reference Type: BACKGROUND

PMID: 33651094 (View on PubMed)

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.

Reference Type: BACKGROUND

PMID: 33644675 (View on PubMed)

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.

Reference Type: BACKGROUND

PMID: 28244665 (View on PubMed)

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.

Reference Type: BACKGROUND

PMID: 17625872 (View on PubMed)

Other Identifiers

Si 148/2025

Identifier Type: -

Identifier Source: org_study_id