Multi-Strain Probiotic Supplementation, Salivary Immunity, and Upper Respiratory Symptoms in Trained Athletes

Overview

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.