Abstract
BackgroundThe use of probiotics in sports has been growing in recent years, as up to 50% of athletes suffer from training- and performance-limiting gastrointestinal (GI) problems. Moreover, repeated exhaustive exercise and high training loads may lead to a transiently depressed immune function, associated with an increased risk of upper respiratory tract infection (URTI).AimTo provide a qualitative analysis of probiotic effects on URTI, GI symptoms and the immune system in healthy individuals under consideration of performance level as main classifier.MethodsA systematic review of the literature was conducted (PubMed, SPORTDiscus with Full Text, Web of Science) to analyze the effects of probiotics in athletes and healthy active individuals on GI problems, URTI, and the immune system. A qualitative synthesis with performance level and treatment duration as main classifiers was performed.ResultsOf 41 eligible studies, 24 evaluated the effects of probiotic supplements in athletes, 10 in recreationally active individuals and 7 in healthy untrained adults. Large heterogeneity was observed in terms of probiotic strains, mode of delivery, performance level, treatment duration and outcome assessment. Overall, studies provided inconsistent observations.ConclusionThe effects of probiotics on immune system, URTI, and GI symptoms in athletes, healthy adults and recreationally active individuals remain inconclusive. Based on the analyzed studies and identified parameters, this article provides suggestions to align future research on the effects of probiotics in exercise.Systematic Review RegistrationPROSPERO, identifier: CRD42021245840.
Highlights
IntroductionThe microbiota (i.e., the communities of commensal, symbiotic and pathogenic microorganisms) is mainly affected by dietary composition and has a significant impact on health (1)
The use of probiotics in sports has been growing in recent years, as up to 50% of athletes suffer from training- and performance-limiting gastrointestinal (GI) problems
While athletes may be more susceptible to GI problems and upper respiratory tract infection (URTI) due to the immunosuppressive effects of repeated intensive exercise (76, 77), recreational exercise does not induce immunosuppressive effects in healthy adults and the beneficial effects of probiotics may be less obvious in this group
Summary
The microbiota (i.e., the communities of commensal, symbiotic and pathogenic microorganisms) is mainly affected by dietary composition and has a significant impact on health (1). Referred to as commensals, part of the gut microorganisms exert specific beneficial effects on the body including improved micro- and macronutrient uptake (2), increased intestinal barrier function, intestinal epithelial cell regeneration, modulation of the immune system, and improved mucosal barrier (3). Probiotic benefits are strain-specific and some strains are more likely to improve health outcomes than others (9). Microorganisms exerting probiotic potential target immune and body cells and regulate immune responses in a beneficial way (10). The specific microbial-derived metabolites, such as short-chain fatty acids (SCFAs), tryptophan, and retinoic acid, have been described to play a central regulatory role in the interaction of the host’s immune response (11). Repeated exhaustive exercise and high training loads may lead to a transiently depressed immune function, associated with an increased risk of upper respiratory tract infection (URTI)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
