An interventional study of Probiotic containing B longum and Probiotic Lactobacillus in Irritable Bowel Syndrome (IBS), sponsored by McMaster University. Enrolling by invitation at 1 site in Canada. Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-10-13.
Sponsored by McMaster University · Not applicable, Interventional, and Treatment
Irritable bowel syndrome (IBS) is characterized by stomach pain and altered bowel habits. It affects about 5 million people in Canada. Doctors don't fully understand what causes IBS, so treatments often don't work well. Many patients say certain foods make their symptoms worse. This may be due to how gut bacteria break down food. Some bacteria produce harmful chemicals like histamine and lysophosphatidylcholine (LPC)/lysophosphatidic acid (LPA), which can cause pain and gut problems. These chemicals may affect about 35% of IBS patients. The goal is to find out which patients have these bacteria. Then, doctors can give them treatments that match their gut bacteria. This could help reduce symptoms and improve their lives. If the study is successful, it could change how we understand, diagnose, and treat IBS, leading to new treatments that focus on personalized microbiota-directed treatments targeting specific causative mechanisms.
Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder characterized by chronic abdominal pain and abnormal bowel habits, affecting 5 million Canadians. Its pathophysiology is incompletely understood and treatments, directed at symptoms, are only 10-15% more effective than a placebo. In the absence of specific mechanistic biomarkers to guide the right treatment for the right patient, clinicians employ the classical "trial-and-error" therapeutical approach. This is often not successful, negatively impacting patients' quality of life and imposing a significant socioeconomic burden.Growing evidence suggests that diet-microbiota interactions play a key role in IBS, leading to low-grade inflammation and symptom genesis. Indeed, up to 84% of IBS patients link their symptoms to ingestion of specific foods. There are likely multiple food-related mechanisms that underlie symptom generation in IBS, including bacterial fermentation of dietary fiber, immunostimulatory effects of proteins contained in wheat, or inflammation-mediated sensitization to food antigens. We recently demonstrated that bacterial production of histamine and/or bioactive phospholipids lysophosphatidyl-choline (LPC) and lysophosphatidic acid (LPA) trigger visceral hyperalgesia and gut dysfunction in subgroups of patients, and which together can account for symptom genesis in approximately 35% of patients with IBS.The concept of precision (personalized) medicine has gained prominence in last few decades, moving away from a 'one-size-fits-all' approach, acknowledging significant variability in disease expression and treatment responses, and recognizing that the conventional approach based on large clinical trials is directed at "average patients". Despite its potential, precision medicine has seen limited adoption in clinical practice. Precision medicine for IBS has not yet been considered, because it is not perceived as life threatening and because of our limited understanding of its causes. However, during the last decade we have made significant strides in understanding the pathophysiology of IBS, identifying gut bacteria and diet as key factors, which can be modified. We recently showed that 20-25% IBS patients have bacteria that convert dietary histidine into histamine, a known pain mediator. Bacterial histamine drives accumulation and activation of mast cells, leading to the development of visceral hypersensitivity. A low fermentable carbohydrate (FODMAP) diet or lactic acid bacteria mitigate these effects by changing the acidity of the colon milieu, as bacterial histidine decarboxylase is highly pH-sensitive. Our on-going pilot study (NCT04364750) suggests that patients' symptoms and bacterial histamine change significantly with 3-day challenges or treatment with mixture of lactobacilli. Further, we found that additional 15-20% patients with IBS have altered bacterial metabolism of dietary phosphatidylcholine (PC) with increased production of LPC and its metabolite LPA, known mediators of neuropathic pain. IBS patient have higher levels of fecal LPC and LPA during periods of severe abdominal pain and mice colonized with their microbiota develop increased pain responses when fed a PC-enriched diet. Altogether, this suggests a synergistic effect between diet and microbiome in symptoms genesis in two subsets of patients with IBS. Therefore, this proposal seeks to establish a transformative process to optimize personalized treatment of patients with IBS, focusing on diet-microbiota interactions as key drivers of symptoms and intestinal pathology. N-of-1 trials, also called "personalized trials," employ a repeated randomized crossover design in a single patient to compare different blinded treatments or challenge effects. This design is most feasible when the treatment/challenge effects have a rapid onset and offset of action, as is the case in IBS patients, especially with food related symptoms. Indeed, these may occur as soon as 15 minutes postprandially, and may last for several hours. In addition, the microbiome and its metabolites are quickly affected by diet and dietary changes, with significant changes occurring within the first 24 hours in an in vitro model and within 48 hours in healthy volunteers. As in traditional crossover trials, carryover effects must be considered with n-of-1 design, but can be addressed through wash-out periods and focusing on the symptoms in the latter part of each treatment period. In general, n-of-1 trials are shorter lasting only months, while conventional randomized controlled trials (RCT) can take up to several years. When a series of n-of-1 trials are conducted in similar patients, the results can be aggregated to produce population-level estimates of treatment effects (equivalent to RCT meta-analyses). In this project, we will first identify IBS patients with histamine and LPC/LPA producing microbiota, and then treat them using "n-of-1" trial design using specific probiotics, either lactic acid-producing bacteria know to inhibit production of histamine through effects on histidine-decarboxylase4 or probiotics impairing conversion of phosphatidylcholine into LPC, in a fast-track bench-to-bedside approach.
1,084 studies on the registry are indexed under Irritable Bowel Syndrome; 196 are open to participants now.
This study's planned enrollment of 30 is below the median of 70 across 869 interventional studies indexed under Irritable Bowel Syndrome.
Browse Irritable Bowel Syndrome studies →McMaster University is the lead sponsor of 738 studies on the registry; 125 are open to participants now.
Of its 7 completed or terminated interventional studies of FDA-regulated products, 3 (43%) have results posted.
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Exclusion Criteria:
Probiotic treatment selected based on the screening results
Dietary Supplement: Probiotic containing B longum · Dietary Supplement: Probiotic Lactobacillus
Capsules similar to treatment containing microcrystalline cellulose
Dietary Supplement: Placebo
This probiotic will be used in the group who have higher levels of LPC and LPA
This probiotic will be used in the group who have higher levels of Histamine
Placebo - microcrystalline cellulose
Reduction in abdominal pain
The visual analog scale (VAS) is a validated, subjective measure for acute and chronic pain. Scores are recorded by making a handwritten mark on a 10-cm line that represents a continuum between "no pain" and "worst pain."
Time frame: Reduction in abdominal pain severity (Visual Analog Scale) comparing probiotic-treatment weeks to placebo-treatment weeks across the 8-week study period.
Improvement in bowel habit satisfaction, bloating, and impact on daily life
The visual analog scale (VAS) assessing improvement in bowel habit satisfaction, bloating, and impact on daily life assessed by Visual Analog Scale
Time frame: Improvement in bowel habit satisfaction, bloating, and impact on daily life (VAS) comparing probiotic-treatment weeks to placebo-treatment weeks across the 8-week study period.
3-month improvement in IBS symptoms
To evaluate sustained treatment effects beyond the acute study period, IBS symptom severity will be assessed at 3-month follow-up using the IBS Symptom Severity Scale (IBS-SSS), a validated instrument measuring overall symptom burden. This assessment compares symptom severity at 3 months post-treatment to baseline measurements, providing insight into the durability and longer-term impact of probiotic treatment on IBS symptom trajectory.
Time frame: Baseline (pre-treatment) to 3-month follow-up (post-intervention)
3-month improvement in somatization
To evaluate the impact of probiotic treatment on psychological symptom manifestation, somatization will be assessed at 3-month follow-up using the Patient Health Questionnaire-15 (PHQ-15), a validated screening instrument measuring somatic symptom burden. This assessment compares somatization scores at 3 months post-treatment to baseline measurements, providing insight into whether probiotic-mediated improvements in gut-brain axis function reduce the psychological distress experienced as physical symptoms.
Time frame: Baseline (pre-treatment) to 3-month follow-up (post-intervention)
3-month improvement in anxiety, depression and stress
To evaluate the impact of probiotic treatment on psychological well-being, anxiety, depression, and stress will be assessed at 3-month follow-up using the Hospital Anxiety and Depression Scale (HADS) and the Depression Anxiety Stress Scales-21 (DASS-21), validated instruments measuring emotional distress. These assessments compare psychological symptom scores at 3 months post-treatment to baseline measurements, providing insight into whether probiotic-mediated improvements in gut-brain axis function reduce the anxiety, depression, and stress burden commonly associated with IBS.
Time frame: Baseline (pre-treatment) to 3-month follow-up (post-intervention)
3-month improvement in Quality of Life
To evaluate the broader impact of probiotic treatment on functional well-being, quality of life will be assessed at 3-month follow-up using the IBS Quality of Life Instrument (IBS-QoL), a validated disease-specific measure of health-related quality of life. This assessment compares quality of life scores at 3 months post-treatment to baseline measurements, providing insight into whether probiotic-mediated improvements in IBS symptoms translate into meaningful gains in daily functioning, social engagement, and overall life satisfaction.
Time frame: Baseline (pre-treatment) to 3-month follow-up (post-intervention)
Reduction of stool pro-nociceptive bacterial metabolites by probiotics
Reduction of stool levels of pro-nociceptive bacterial metabolites (histamine, LPC/LPA) by probiotics
Time frame: Reduction in specific bacterial comparing probiotic-treatment weeks to placebo-treatment weeks across the 8-week study period.
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Plan to share: Undecided
Start is estimated for Oct 2026; primary completion for Apr 2028, 18 months later.
Of 297 non-industry interventional studies with no phase under Irritable Bowel Syndrome, half reached primary completion within 21 months of starting (the median), counting those still running; a quarter within 9 and three quarters within 39. This study's planned 18 months is below that.
Counting every sponsor, half of 345 studies reached it within 19 months; a quarter within 9 and three quarters within 38.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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