Irritable Bowel Syndrome (IBS)NCT06871748
Effect of a Low FODMAP Diet in IBS and Functional Constipation with Bloating: a Randomized Double-Blind Trial
A study testing Low FODMAP Diet and High FODMAP Diet in people with Irritable Bowel Syndrome (IBS) and Constipation - Functional, run by Mahidol University.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Irritable Bowel Syndrome (IBS), Constipation - Functional, Bloating
- What is being tested?
- Low FODMAP Diet and High FODMAP Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 34 participants
- Where
- No sites listed yet
- Study dates
- 15 Mar 2025to 31 Jul 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Official title: Effect of a Low FODMAP Diet in Irritable Bowel Syndrome and Functional Constipation with Bloating: a Randomized Double-Blind Controlled Trial with Microbiota, Intestinal Gas, and Metabolomic Analysis
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.
Read more
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.
Read the 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.
- Being tested
- Low FODMAP Diet, High FODMAP Diet
- Keywords
- Irritable Bowel Syndrome (IBS), Functional Constipation, FODMAP, Microbiota
- Medical subject headings
- Irritable Bowel Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low FODMAP DietOther
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 DietOther
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.
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: 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. Receives: Other: High FODMAP Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: Baseline to 2 weeks (End of Intervention)
Secondary outcomes (15)
Reduction in Global IBS Symptoms (IBS-SSS)
Change in IBS Symptom Severity Score (IBS-SSS) from baseline, assessing overall IBS symptom burden, abdominal pain, bloating, and bowel habit changes. The IBS-SSS scale ranges from 0 to 500, with higher scores indicating more severe IBS symptoms.
Measured: Baseline to 2 weeks
Change in Abdominal Pain (VAS)
Change in abdominal pain severity, measured using the Visual Analog Scale (VAS). The VAS scale ranges from 0 (no pain) to 10 (severe pain), with higher scores indicating worse pain severity. Participants will record daily pain scores, and the difference between baseline and post-intervention scores will be analyzed.
Measured: Baseline to 2 weeks
Change in Stool Frequency and Consistency
Change in bowel movement frequency and stool consistency, assessed using the Bristol Stool Form Scale (BSFS).
Stool frequency will be recorded as the number of bowel movements per day.
Stool consistency will be graded using the BSFS scale (1-7):
1-2: Hard stools (constipation) 3-4: Normal stools 5-7: Loose stools (diarrhea) Higher BSFS scores indicate looser stool consistency. The difference between baseline and post-intervention values will be analyzed.
Measured: Baseline to 2 weeks
Changes in Gut Microbiota Composition
Alterations in gut microbiota diversity and abundance (16S rRNA sequencing).
Measured: Baseline to 2 weeks
Change in Hydrogen Gas Production (Lactulose Breath Test)
Change in exhaled hydrogen (H₂) levels, measured via lactulose breath test in parts per million (ppm). Higher hydrogen levels indicate increased fermentation by colonic microbiota.
Measured: Baseline to 2 weeks
Change in Methane Gas Production (Lactulose Breath Test)
Change in exhaled methane (CH₄) levels, measured via lactulose breath test in parts per million (ppm). Elevated methane levels are associated with slow colonic transit and constipation.
Measured: Baseline to 2 weeks
Use of Rescue Medications
Frequency and dosage of antispasmodics, prokinetics, or laxatives used for symptom relief.
Measured: Baseline to 2 weeks
Change in Psychological Symptoms (DASS-21)
Change in Depression, Anxiety, and Stress Scores (DASS-21), a validated self-reported scale measuring psychological distress. The DASS-21 consists of three subscales:
Depression (0-21) Anxiety (0-21) Stress (0-21) Each subscale score ranges from 0 (normal) to 21 (severe symptoms), with higher scores indicating greater psychological distress. The total score is calculated by summing individual subscale scores.
Measured: Baseline to 2 weeks
Change in Quality of Life (IBS-QoL / PAC-QoL)
Change in IBS-specific Quality of Life (IBS-QoL) score, which assesses the impact of IBS on daily activities, emotional well-being, and social functioning.
The IBS-QoL score ranges from 0 to 100, with higher scores indicating better quality of life.
Measured: Baseline to 2 weeks
Patient Satisfaction with Treatment
Overall treatment satisfaction, measured using a Visual Analog Scale (VAS) ranging from 0 to 10:
0 = Completely Dissatisfied 10 = Completely Satisfied Higher scores indicate greater satisfaction with treatment. The difference between baseline and post-intervention scores will be analyzed.
Measured: Baseline to 2 weeks
Change in Patient-Reported Constipation Symptoms (PAC-SYM)
Change in Patient Assessment of Constipation-Symptoms (PAC-SYM) score, evaluating constipation-related symptoms, including stool consistency, discomfort, and straining. The PAC-SYM scale ranges from 0 to 48, with higher scores indicating worse constipation symptoms.
Measured: Baseline to 2 weeks
Change in Short-Chain Fatty Acids (SCFAs) Levels
Change in fecal short-chain fatty acids (SCFAs), including acetic acid, propionic acid, and butyric acid, measured in μmol/g stool. Higher SCFA levels indicate greater microbial fermentation activity.
Measured: Baseline to 2 weeks
Change in Urine Histamine Levels
Change in urine histamine concentration, measured in μg/mL urine, assessing histamine metabolism related to gut inflammation and microbiota activity. Higher levels indicate increased histamine production.
Measured: Baseline to 2 weeks
Change in Urine Azelaic Acid Levels
Change in urine azelaic acid concentration, measured in μg/mL urine, assessing microbial metabolic changes associated with gut dysbiosis and inflammation. Higher levels indicate altered microbial metabolism.
Measured: Baseline to 2 weeks
Change in Constipation-Specific Quality of Life (PAC-QoL)
Change in Patient Assessment of Constipation-Quality of Life (PAC-QoL) score, evaluating the impact of constipation on daily life, physical discomfort, psychological well-being, and social aspects.
The PAC-QoL score ranges from 0 to 100, with higher scores indicating better quality of life.
Measured: Baseline to 2 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 Mar 2025
- Study start15 Mar 2025 (estimated)
- Primary completion15 Mar 2026 (estimated)
- Study completion31 Jul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (5)Papers the sponsor has linked to this study.
- Other trials for Irritable Bowel Syndrome (IBS)Studies of the same condition, open and under way.
- More trials run by Mahidol UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- 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.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 34 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Mahidol University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Watcharasak Chotiyaputta, Mahidol University
- Investigators
- Monthira Maneerattanaporn, MD, Study director, Mahidol University Faculty of Medicine Siriraj HospitalTanawat Geeratragool, MD, Principal investigator, Mahidol University Faculty of Medicine Siriraj HospitalSomchai Leelakusolvong, MD, Study chair, Mahidol University Faculty of Medicine Siriraj Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06871748
- Sponsor's protocol ID
- Si 148/2025
- Status last verified
- Feb 2025
- First submitted
- 28 Feb 2025
- Last updated
- 12 Mar 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
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.
PubMed 34808139Camilleri M. Diagnosis and Treatment of Irritable Bowel Syndrome: A Review. JAMA. 2021 Mar 2;325(9):865-877. doi: 10.1001/jama.2020.22532.
PubMed 33651094Andrews 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.
PubMed 33644675Varney 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.
PubMed 28244665Muir 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.
PubMed 17625872
Study at a glance
From the registry record, last updated by the sponsor on 12 Mar 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of a Low FODMAP Diet in Irritable Bowel Syndrome and Functional Constipation with Bloating: a Randomized Double-Blind Controlled Trial with Microbiota, Intestinal Gas, and Metabolomic Analysis
- ClinicalTrials.gov ID
- NCT06871748
- Acronym / sponsor ID
- Si 148/2025
- Keywords
- Irritable Bowel Syndrome (IBS), Functional Constipation, FODMAP, Microbiota
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 34 participants (estimated)
- Lead sponsor
- Mahidol UniversityUniversity, hospital or other
- Study start
- 15 Mar 2025 (estimated)
- Primary completion
- 15 Mar 2026 (estimated)
- Study completion
- 31 Jul 2026 (estimated)
- First posted
- 12 Mar 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- 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.
| Arm | Type | Receives |
|---|---|---|
| Low FODMAP Diet | Experimental | Other: Low FODMAP DietParticipants 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. |
| High FODMAP Diet | Active comparator | Other: High FODMAP DietParticipants 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. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- 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)
Key exclusion criteria (4 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Low FODMAP DietA 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. | Other | Low FODMAP Diet |
| High FODMAP DietA 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. | Other | High FODMAP Diet |
Primary outcome
Change in Bloating Severity (VAS)
Time frame: Baseline to 2 weeks (End of Intervention)
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.
15 secondary outcomes
Reduction in Global IBS Symptoms (IBS-SSS)
Time frame: Baseline to 2 weeks
Change in Abdominal Pain (VAS)
Time frame: Baseline to 2 weeks
Change in Stool Frequency and Consistency
Time frame: Baseline to 2 weeks
Changes in Gut Microbiota Composition
Time frame: Baseline to 2 weeks
Change in Hydrogen Gas Production (Lactulose Breath Test)
Time frame: Baseline to 2 weeks
Change in Methane Gas Production (Lactulose Breath Test)
Time frame: Baseline to 2 weeks
Use of Rescue Medications
Time frame: Baseline to 2 weeks
Change in Psychological Symptoms (DASS-21)
Time frame: Baseline to 2 weeks
Change in Quality of Life (IBS-QoL / PAC-QoL)
Time frame: Baseline to 2 weeks
Patient Satisfaction with Treatment
Time frame: Baseline to 2 weeks
Change in Patient-Reported Constipation Symptoms (PAC-SYM)
Time frame: Baseline to 2 weeks
Change in Short-Chain Fatty Acids (SCFAs) Levels
Time frame: Baseline to 2 weeks
Change in Urine Histamine Levels
Time frame: Baseline to 2 weeks
Change in Urine Azelaic Acid Levels
Time frame: Baseline to 2 weeks
Change in Constipation-Specific Quality of Life (PAC-QoL)
Time frame: Baseline to 2 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 12 Mar 2025.
- Background: PubMed 34808139Drossman 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.
- Background: PubMed 33651094Camilleri M. Diagnosis and Treatment of Irritable Bowel Syndrome: A Review. JAMA. 2021 Mar 2;325(9):865-877. doi: 10.1001/jama.2020.22532.
- Background: PubMed 33644675Andrews 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.
- Background: PubMed 28244665Varney 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.
- Background: PubMed 17625872Muir 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.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Monthira Maneerattanaporn, MD study director
Mahidol University Faculty of Medicine Siriraj Hospital
Tanawat Geeratragool, MD principal investigator
Mahidol University Faculty of Medicine Siriraj Hospital
Somchai Leelakusolvong, MD study chair
Mahidol University Faculty of Medicine Siriraj Hospital
Questions about this trial
What is this clinical trial studying?
A study testing Low FODMAP Diet and High FODMAP Diet in people with Irritable Bowel Syndrome (IBS) and Constipation - Functional, run by Mahidol University.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 12 Mar 2025. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Monthira Maneerattanaporn, MD (662419777, monthira.man@mahidol.ac.th), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in Bloating Severity (VAS) (time frame: Baseline to 2 weeks (End of Intervention)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06871748, which also lists 5 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Mar 2025.