An interventional study of Multi-Strain Probiotic and Rice Flour Placebo in Upper Respiratory Symptoms and Mucosal Immunity, sponsored by University of Ulster. Completed at 1 site in United Kingdom. Open to participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-24.
Sponsored by University of Ulster · Not applicable, Interventional, and Prevention
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This completed external pilot study assessed the feasibility of conducting a randomised, double-blind, placebo-controlled trial of four-week multi-strain probiotic supplementation in trained athletes. Participants were allocated to receive either one probiotic capsule containing 20 billion colony-forming units or a matched rice-flour placebo capsule daily for 28 days. Feasibility measures included recruitment, retention, supplementation adherence and completion of daily monitoring records. Preliminary biological and symptom outcomes included salivary secretory immunoglobulin A and upper respiratory symptom burden. The findings were intended to inform the design of a future definitive randomised controlled trial and were not intended to provide a definitive assessment of efficacy.
This study was conducted as a randomised, double-blind, placebo-controlled, parallel-group external pilot trial. Trained athletes were allocated in a 1:1 ratio to a probiotic group or a placebo group for 28 days.
Participants assigned to the probiotic group consumed one Elite Pro 20 Biotic capsule daily. Each capsule provided 20 billion colony-forming units and contained Bifidobacterium lactis Bl-04, Lactobacillus paracasei Lpc-37, Lactobacillus acidophilus NCFM, Bifidobacterium lactis Bi-07 and Bifidobacterium bifidum Bb-02. Participants assigned to the control group consumed one visually matched capsule containing rice flour daily. Participants and investigators remained blinded to treatment allocation during data collection.
Participants completed daily upper respiratory symptom and training-monitoring records throughout the intervention. Saliva samples were collected at baseline and after 28 days, both before and immediately after a standardised treadmill exercise challenge. Salivary secretory immunoglobulin A was assessed as a marker of mucosal immunity.
The principal purpose of this external pilot was to assess study feasibility, including recruitment, retention, supplementation adherence, capsule return and completion of monitoring records. Salivary secretory immunoglobulin A and upper respiratory symptom outcomes were examined to generate preliminary estimates and inform the methods and sample-size planning of a future definitive trial. A conventional efficacy-based sample-size calculation was therefore not undertaken, and the outcome findings were considered exploratory and hypothesis-generating.
64 studies on the registry are indexed under Signs and Symptoms, Respiratory; 9 are open to participants now.
This study's enrollment of 15 is below the median of 120 across 43 interventional studies indexed under Signs and Symptoms, Respiratory.
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Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants received one Elite Pro 20 Biotic multi-strain probiotic capsule containing 20 billion CFU once daily for 28 days.
Dietary Supplement: Multi-Strain Probiotic
Participants received one visually matched capsule containing rice flour once daily for 28 days.
Dietary Supplement: Rice Flour Placebo
One oral capsule was taken daily for 28 days. Each capsule provided 20 billion colony-forming units and contained Lactobacillus acidophilus NCFM, Lactobacillus paracasei Lpc-37, Bifidobacterium lactis Bl-04, Bifidobacterium lactis Bi-07, and Bifidobacterium bifidum Bb-02
One visually matched oral capsule containing rice flour and no live microorganisms was taken daily for 28 days.
Resting Salivary Secretory Immunoglobulin A Concentration
Saliva was collected immediately before a standardised treadmill exercise challenge at baseline and after 28 days of supplementation. Secretory immunoglobulin A concentration was measured using an enzyme-linked immunosorbent assay. Day 28 resting sIgA was compared between groups while accounting for baseline resting sIgA.
Time frame: Baseline and Day 28
Plan to share: No — Individual participant data will not be shared publicly or with external researchers. Data will be stored securely in accordance with Ulster University research governance, GDPR requirements, and the approved ethics protocol. Only authorised members of the research team will have access to coded study data. Results will be reported only in anonymised aggregate form in publications and presentations.
No publications or documents are linked to this record.
Ran from May 2025 to primary completion in Dec 2025, 7 months.
Of 18 interventional studies with no phase under Signs and Symptoms, Respiratory, half reached primary completion within 12 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 26. This study's 7 months is below that.
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This study is completed, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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