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Irritable Bowel SyndromeEarly Phase 1NCT04364750

Biomarkers of Diet-microbiota Interactions in Irritable Bowel Syndrome

A Early Phase 1 study testing L-Histidine, High-FODMAP beverage and Low-FODMAP beverage in people with Irritable Bowel Syndrome, run by McMaster University at 2 sites in Canada.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

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… Read more about this study

Who is it for?
Ages 18 to 75 years
Conditions the study is for
Irritable Bowel Syndrome
What is being tested?
L-Histidine, High-FODMAP beverage and Low-FODMAP beverage
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
30 participants
Where
2 sitesCanada
Study dates
15 Jul 2021to 10 Feb 2026
Phase
Early Phase 1
Are there results?
None posted in the registry

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 to 75 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • 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.

Who cannot join

  • 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
Show all 9Show fewer
  • 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

Trial locations and contacts

2 sites in 1 country.

Canada2 sites

  • McMaster University Medical Centre

    Hamilton, Ontario, L8N 3Z5

  • Kingston Health Sciences Centre

    Kingston, Ontario, K7L 2V7

Other trials in Canada

About this study

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.

Being tested
L-Histidine, High-FODMAP beverage, Low-FODMAP beverage, Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2., Placebo
Keywords
FODMAP, microbiota, histamine
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.

  • L-HistidineDietary supplement

    1 capsule (0.6g) twice daily

  • High-FODMAP beverageDietary supplement

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

  • Low-FODMAP beverageDietary supplement

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

  • Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2.Dietary supplement

    Also called Bio-K+ 50 Billion

    Total of 50 billion CFU/capsule taken twice daily.

  • PlaceboOther

    Enteric coated capsule with no active ingredient, taken twice daily

Study groups in NCT04364750
Study groupRoleWhat they receive
Group AExperimentalParticipants in group A will undergo challenges in the order: 1. High-FODMAP beverage + placebo probiotic + L-Histidine 2. Low-FODMAP beverage + placebo probiotic + L-Histidine 3. High-FODMAP beverage + probiotic + L-Histidine Challenges each last 5 days, but the FODMAP drinks and the L-Histidine capsules are only taken for the last three days. There is a 10 day washout period between challenges.
Receives: Dietary Supplement: L-Histidine; Dietary Supplement: High-FODMAP beverage; Dietary Supplement: Low-FODMAP beverage; Dietary Supplement: Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2.; Other: Placebo
Group BExperimentalParticipants in group A will undergo challenges in the order: 1. Low-FODMAP beverage + placebo probiotic + L-Histidine 2. High-FODMAP beverage + probiotic + L-Histidine 3. High-FODMAP beverage + placebo probiotic + L-Histidine. Challenges each last 5 days, but the FODMAP drinks and the L-Histidine capsules are only taken for the last three days. There is a 10 day washout period between challenges.
Receives: Dietary Supplement: L-Histidine; Dietary Supplement: High-FODMAP beverage; Dietary Supplement: Low-FODMAP beverage; Dietary Supplement: Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2.; Other: Placebo
Group CExperimentalParticipants in group A will undergo challenges in the order: 1. High-FODMAP beverage + probiotic + L-Histidine 2. High-FODMAP beverage + placebo probiotic + L-Histidine 3. Low-FODMAP beverage + placebo probiotic + L-Histidine. Challenges each last 5 days, but the FODMAP drinks and the L-Histidine capsules are only taken for the last three days. There is a 10 day washout period between challenges.
Receives: Dietary Supplement: L-Histidine; Dietary Supplement: High-FODMAP beverage; Dietary Supplement: Low-FODMAP beverage; Dietary Supplement: Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2.; Other: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Metabolites in stool, urine and blood

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

    Measured: six weeks

Secondary outcomes (7)

  1. Expression of hdc gene by stool bacteria

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

    Measured: six weeks

  2. Stool microbiota composition

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

    Measured: six weeks

  3. Worsening of IBS symptoms following High-FODMAP challenge

    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.

    Measured: six weeks

  4. Changes in IBS symptoms

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

    Measured: six weeks

  5. Changes in general GI symptoms

    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.

    Measured: six weeks

  6. Levels of anxiety, depression and stress

    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.

    Measured: six weeks

  7. Changes in dietary intake

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

    Measured: six weeks

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted28 Apr 2020
  2. Study start15 Jul 2021
  3. Primary completion10 Feb 2026
  4. Study completion10 Feb 2026

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Early Phase 1
Primary purpose
Other
Allocation
Randomised
Intervention model
Crossover
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
30 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04364750
Sponsor's protocol ID
BFIBS
Status last verified
Apr 2026
First submitted
23 Apr 2020
Last updated
13 Apr 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Early Phase 1 study testing L-Histidine, High-FODMAP beverage and Low-FODMAP beverage in people with Irritable Bowel Syndrome, run by McMaster University at 2 sites in Canada.

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 1 inclusion and 9 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: finished, as of the sponsor's last update on 13 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 2 sites in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.

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.

What does this phase mean?

Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Metabolites in stool, urine and blood (time frame: six weeks). 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 NCT04364750.

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 13 Apr 2026.

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