Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by recurrent abdominal pain and altered bowel habits, often associated with impaired intestinal barrier function, low-grade inflammation, and dysregulation of the gut-brain axis. Postbiotics have emerged as a promising therapeutic approach due to their immunomodulatory, anti-inflammatory, and gut barrier-protective properties.

This completed single-arm, open-label clinical study evaluated the efficacy of PosBion® postbiotic supplementation in adults with IBS over a 12-week intervention period. The study assessed changes in IBS symptom severity, quality of life, gastrointestinal health, inflammatory biomarkers, intestinal barrier integrity, mucosal immunity, oxidative stress, and gut-brain axis biomarkers using validated questionnaires and salivary biomarker analyses.

Irritable bowel syndrome (IBS) is one of the most prevalent disorders of gut-brain interaction, affecting millions of individuals worldwide and substantially impairing quality of life. Increasing evidence suggests that IBS is associated with intestinal dysbiosis, impaired intestinal barrier function, microbial translocation, low-grade inflammation, oxidative stress, altered mucosal immunity, and dysregulation of the gut-brain axis. These interconnected mechanisms represent important therapeutic targets for nutritional interventions.

Postbiotics, consisting of inactivated microorganisms and their bioactive components, have attracted increasing attention due to their safety, stability, and potential health benefits. Experimental and clinical studies suggest that postbiotics may improve intestinal homeostasis by strengthening epithelial barrier integrity, modulating immune responses, suppressing intestinal inflammation, and regulating host-microbiota interactions.

This completed prospective, single-arm, open-label clinical study investigated the efficacy of PosBion® postbiotic supplementation in adults with IBS. Fifty-five subjects were enrolled, of whom fifty completed the 12-week intervention. Subjects consumed two sachets of PosBion® daily throughout the study period.

Clinical efficacy was evaluated using the Irritable Bowel Syndrome Symptom Severity Scale (IBS-SSS), Irritable Bowel Syndrome Quality of Life (IBS-QOL) questionnaire, and a gastrointestinal health visual analogue scale (GI Health VAS). To investigate the potential mechanisms underlying the intervention, serial saliva samples were collected at baseline and during follow-up visits for biomarker analyses.

Inflammatory responses were assessed by measuring salivary calprotectin, interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), lactoferrin, and myeloperoxidase (MPO). Intestinal barrier integrity and intestinal permeability were evaluated using salivary zonulin, lipopolysaccharide (LPS), and lipopolysaccharide-binding protein (LBP). Mucosal immune function was assessed using secretory immunoglobulin A (sIgA), while oxidative stress was evaluated by measuring salivary malondialdehyde (MDA). Gut-brain axis responses were assessed using salivary cortisol and serotonin.

The study aimed to determine whether PosBion® supplementation could improve clinical outcomes in IBS while modulating biomarkers associated with intestinal inflammation, barrier integrity, mucosal immunity, oxidative stress, and gut-brain axis function, thereby providing mechanistic evidence supporting the therapeutic potential of postbiotics in IBS.

Inclusion Criteria:

• Experienced one or more symptoms consistent with irritable bowel syndrome (IBS), including:
• Stomach pain or abdominal cramps
• Bloating
• Excessive gas
• Diarrhoea
• Constipation (or alternating diarrhoea and constipation)
• Mucus in stool
• Urgency to defecate
• Sensation of incomplete bowel evacuation
• Willing and able to comply with all study procedures and scheduled visits.
• Provided written informed consent before study participation.

Exclusion Criteria:

• History of chronic or serious medical conditions, including but not limited to diabetes mellitus, cardiovascular disease, chronic kidney disease, cancer, or chronic respiratory disease.
• Current use of supplements intended to improve gut health.
• Current use of antibiotics or antiviral medications.
• Current use of probiotic, prebiotic, or postbiotic supplements.
• Major surgery within the previous 6 months.
• Pregnant or breastfeeding women.
• Known allergy or hypersensitivity to any ingredient of the investigational product.
• Any condition that, in the opinion of the investigators, could interfere with study participation, compliance, or interpretation of the study results.

De-identified individual participant data underlying the results reported in the published articles, including demographic characteristics, clinical outcome measures, questionnaire scores, and biomarker data, will be made available to qualified researchers upon reasonable request. Requests must be accompanied by a scientifically sound research proposal and will be subject to approval by the principal investigator and study sponsor to ensure participant confidentiality and compliance with applicable ethical and institutional requirements. Data will become available beginning 6 months after publication of the primary study results and will remain available for 5 years.

Six months after publication of the primary study results and will remain available for 5 years.

Qualified researchers with a scientifically sound research proposal will be eligible. Access requests will be reviewed and approved by the principal investigator and study sponsor.