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Completed

NCT Number: NCT04364750

Biomarkers of Diet-microbiota Interactions in Irritable Bowel Syndrome

Most patients suffering from the irritable bowel syndrome (IBS) report that ingestion of certain foods is a major trigger of symptoms, but the reason is unclear. Previous studies have shown that foods containing poorly absorbed carbohydrates (FODMAPs) are fermented by the bacteria in our bowels and these cause symptoms in some but not all patients. Gut bacteria are capable of producing various products, such as neuroimmune mediator histamine, that may be related to IBS symptoms. Our recent data suggest that consumption of FODMAPs promotes production of bacterial histamine.

The main objective of this study is to investigate bacterial production of histamine and its relationship to IBS symptoms. The study will involve 6 weeks on a low-FODMAP diet with three three-day interventions consisting of High- or Low-FODMAP drinks along with probiotics or placebo capsules. The patient's bacteria and metabolites will be analyzed at various time points.

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Key information

Conditions

Irritable Bowel Syndrome Colonic Diseases Colonic Diseases, Functional Digestive System Diseases Gastrointestinal Diseases Intestinal Diseases

Age range

18 year–75 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Early Phase 1

Primary location

McMaster University Medical Centre, Hamilton, Ontario, Canada

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Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18-75 with IBS (Rome IV criteria) who have self-reported previous improvement in their IBS symptoms while on a low FODMAP diet, or when excluding certain high-FODMAP foods, or patients in whom histamine is expected to play a key role (either diagnosed with high histamine producing bacteria, or improved IBS symptoms after using antihistamines). Individuals should be able to swallow size 00 capsules.

Exclusion criteria

  • Concurrent significant organic GI pathology (i.e. celiac, IBD, etc.)
  • Concurrent systemic disease (such as diabetes) and/or laboratory abnormalities considered by investigators to be risky or that could interfere with data collection
  • History of active cancer in the last 5 years, other than basal cell cancer
  • Pregnant or breastfeeding women
  • Active or recent participation (< 1 month) in a clinical study, except for SPOR IMAGINE
  • Use of antibiotics, probiotics, or ACE inhibitors during, or one month prior to the study
  • Use of new medications less than 4 weeks prior to the study.
  • Allergies to any of the ingredients used in the study
  • Any immune-compromising conditions

Treatment and study plan

L-Histidine

Dietary Supplement

1 capsule (0.6g) twice daily

High-FODMAP beverage

Dietary Supplement

High-FODMAP beverage (10g of fermentable carbohydrates) consumed twice daily.

Low-FODMAP beverage

Dietary Supplement

Low-FODMAP beverage (10g glucose) consumed twice daily.

Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2.

Dietary Supplement

Total of 50 billion CFU/capsule taken twice daily.

Other names: Bio-K+ 50 Billion

Placebo

Other

Enteric coated capsule with no active ingredient, taken twice daily

Primary outcomes

  1. Metabolites in stool, urine and blood

    Time frame: six weeks

    Metabolites will be measured by LC-MS and ELISA at baseline and before and after each intervention.

Secondary outcomes

  1. Expression of hdc gene by stool bacteria

    Time frame: six weeks

    Gram-positive and Gram-negative bacteria will be assessed by PCR using custom designed primers

  2. Stool microbiota composition

    Time frame: six weeks

    16S rRNA Illumina sequencing of stool samples with culture-enriched sequencing.

  3. Worsening of IBS symptoms following High-FODMAP challenge

    Time frame: six weeks

    Increase by ≥50 points on IBS Symptom Severity Score (IBS-SSS). The score will be used as a dichotomous variable. The overall score ranges from 0 to 500, with higher scores indicating greater symptom severity.

  4. Changes in IBS symptoms

    Time frame: six weeks

    IBS-SSS continuous data. The overall score ranges from 0 to 500, with higher scores indicating greater symptom severity.

  5. Changes in general GI symptoms

    Time frame: six weeks

    Patient-Reported Outcomes Measurement Information System (PROMIS) for general GI symptoms. Four subscales will be used: Gas & Bloating, Diarrhea, Constipation, and Belly Pain. T-scores are calculated using the Scoring Service by Health Measures and range from 34.7 - 79.0 (Gas & Bloating), 39.9 - 75.2 (Diarrhea), 40.6 - 80.8 (Constipation), and 33.9 - 80.0 (Belly Pain). On this scale, 50 indicates the mean of the general population and a difference of 10 is a standard deviation. Higher scores indicate greater symptom severity.

  6. Levels of anxiety, depression and stress

    Time frame: six weeks

    Depression Anxiety Stress Scale (DASS-21) to assess psychiatric comorbidity and stress. The scale scores range from 0 - 42 with higher scores indicating worse outcomes.

  7. Changes in dietary intake

    Time frame: six weeks

    5-day food diaries will be completed at 5 time points. FODMAP intake will be quantified using Monash University software and database

Sponsors and collaborators

Lead sponsor

McMaster University

Other

Registry information

Important dates

Study start
2021
Primary completion
2026
Study completion
2026
First posted
Apr 28, 2020
Registry last updated
Apr 13, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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