The effect of probiotics on the incidence, duration and severity of illness in elite rugby players

Abstract

Background: Athletes partaking in prolonged intense exercise, particularly elite athletes may have higher susceptibility of upper respiratory tract infections (URTI), than individuals participating in moderate or no exercise. Illness can negatively impact on training and performance; therefore it is important to investigate ways to attenuate the risk of infection. Numerous health claims have been associated to probiotics, most focusing on their beneficial effects on the immune system, and/or the gastrointestinal tract. Probiotics modify the gut microbiota and have been shown to increase some aspects of mucosal and systemic immunity. A number of studies have indicated probiotics may reduce the number, duration and severity of illness in the general population. However, there is less evidence regarding the benefits of probiotics in athletes, especially among team sports. Objective: The aim of this clinical trial was to study the effects of Probiotics (Probiotica P3) on the incidence, severity and duration of upper respiratory tract infections (URTI), and gastrointestinal (GI) symptoms amongst elite “Super 15” rugby players during training and competition. Method: The study was a randomised, single-blind, placebo-controlled, crossover trial with two arms: probiotics (Probiotica P3) and placebo. A total of 34 participants from an elite rugby squad in New Zealand were recruited and randomly assigned to the treatment groups. Each treatment lasted four weeks, and were separated by a 4 week washout period. On a daily basis throughout each treatment, each player completed an “incidence” dairy recording any URTI and GI symptoms and the severity of these during the past 24 hours. On both treatments one capsule was provided daily. Probiotic capsules contained a dose of 3.0 x 109 colony-forming units (CFUs) including three strains of bacteria; Lactobacillus gasseri, Bifidobacterium bifidum, Bifidobacterium longum. Results: Probiotic supplementation resulted in a significantly lower incidence of any symptoms (URTI or GI) compared to the placebo, 16 episodes vs. 24 episodes (p=0.03). There was a tendency for fewer days of illness on the probiotic treatment compared to the placebo (p=0.054). The mean duration of ‘all’ symptoms was significantly reduced on the probiotic treatment (1.51 days vs. 2.91 days, p=0.031). In addition, the mean duration for episodes of illness was significantly reduced for URTI symptoms on the probiotic treatment compared to the placebo (1.90 days vs. 4.39 days, p=0.050).There were no significant differences in severity of symptoms between the two groups. The mean severity score for all symptoms was 8.77 ± 2.66 whilst on the probiotic and 13.33 ± 4.58 (p=0.110) on the placebo. Conclusion: Probiotica P3 supplementation was associated with a significant reduction in illness incidence and duration in highly trained Super 15 rugby players, but did not significantly affect the severity of illness symptoms. Thus, probiotics may be useful nutritional supplementation for sports teams as a means of reducing illness.