Probiotic strategy to reduce infections in athletes

AliciaDavies's picture

A double-blind, randomised, controlled, clinical trial has highlighted the benefits of two practitioner-only supplements in reducing respiratory and gastrointestinal infections in elite athletes. The supplements, including a high-strength probiotic formulation with 60 billion CFU (combining 10 probiotic strains and 25 billion CFU of the clinically trialled LAB4 strains) and Sacharomyces boulardii, returned interesting results in a largely uncovered area of nutritional science.

The trial, published in the Journal of Science and Medicine in Sport, examined 19 elite rugby union players who partook in the 27-week trial during Australian winter, with the purpose of seeing if probiotic supplementation could improve the immune response of elite international competing athletes.

It is well-known and documented that elite athletes are more susceptible to illness due to international travel and the high level of physical and mental stress endured as a result of high intensity exercise in training and competition. Respiratory and gastrointestinal illnesses are the most common medical presentation to sports medicine clinicians (after injury) among elite athletes. In the most recent summer Olympics, 5% of athletes competing became ill throughout the competition, of which 68% of the illnesses were due to respiratory and gastrointestinal infections (47% respiratory and 21% gastrointestinal).

In the trial, athletes in the probiotic group were administered one 60 billion CFU probiotic capsule twice daily for 17 weeks, whilst the placebo group took one capsule with identical excipients only twice daily for 17 weeks. During the international phase of the trial (stage 3), the probiotic group also ingested 250mg of Sacharomyces boulardii twice daily. An additional two identical capsules made of only excipients were also administered to the placebo group. Throughout the study, salivary biomarkers of all trial participants were measured twice weekly including salivary cortisol, salivary immunoglobulin A (sIgA) and salivary alpha amylase (sAA).

At the end of the 27-week trial period, there was a total of five recorded incidences of illness and infection diagnosed by the team’s sports physician. Of these, there were four cases of upper respiratory tract infections (URTI) and one case of gastrointestinal illness. Of the group taking the probiotics, none of the athletes reported, or were diagnosed with, any illness during the 17-week intervention period. Whilst there were no notable differences in salivary cortisol or sIgA levels between the two groups, what was statistically significant was the increased sAA levels of the probiotic group. sAA can have dual actions, one being a compensatory immune affect. sAA is also an indicator of autonomic nervous system (ANS) response. When the players were stressed and had chronically high cortisol levels, the sAA exhibited a protective effect. It is thought the probiotics have this effect on the immune pathway by enabling the secretion of sAA. Several in vitro and animal studies have demonstrated the effect of probiotic strains on the expression of mucins and host defence proteins, however, the role of sAA in host defences is largely unexplored in studies evaluating the markers of mucosal immunity in athletes, highlighting the significance of this study’s findings.

The trial found that probiotics are beneficial in reducing gastrointestinal and upper respiratory tract infections. The international rugby union players were travelling, subjected to disruption in sleep pattern circadian rhythms (known to compromise the immune system) and under high degrees of physical and emotional stress. The overall low incidence of illness amongst both groups as also noted, with the researchers hypothesising that the probiotics had a ‘herd immunity’ effect on the placebo group.


  1. Pumpa KL, McKune AG, Harnett J. A novel role of probiotics in improving host defence of elite rugby union athlete: a double blind randomised controlled trial. J Sci Med Sport 2019;S1440-2440(18)31160-5. [Abstract]


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Alicia Davies

Alicia is a qualified Naturopath, Nutritionist and Medical Herbalist. She has been in clinical practice for over 10 years with a passion for digestive disorders, thyroid disorders, autoimmune disorders, insomnia and DNA genetic interpretation. Alicia is driven by health in the community with a goal to educate and empower individuals to lead a healthy life.