Probiotics, prebiotics and synbiotics: useful for athletes and active individuals? A systematic review

The purpose of this review was to synthesise available knowledge on the main health effects associated with the use of probiotics, prebiotics and/or synbiotics in athletes and active individuals, including their effects on the immune system, oxidative stress, the gastrointestinal and respiratory symptoms, as well as other possible clinical outcomes. A systematic and comprehensive search in electronic databases, including Web of Science (WOS, Scielo), PubMed-MEDLINE, Biblioteca virtual de la Salud (LILACS, IBECS), EBSCO (Academic Search Complete CINAHL; SPORTDiscus) and Cochrane Library, focused on generic articles about probiotics, prebiotics and/or synbiotics and their functionality and effects on human health. The search process was completed using the keywords: 'probiotics', 'prebiotics', 'synbiotics', 'athletes' and 'health'. The only exclusion criterion was experimental studies with animals. A total of 31 studies met the inclusion criteria and were included in the review. The vast majority were experimental studies about probiotics and health effects (n=28), while only a few demonstrated the results of consuming prebiotics and/or synbiotics (n=3) in athletes and active individuals. Although most of the studies reported positive health effects in athletes and active individuals, there is still no substantial scientific evidence to suggest that probiotics, prebiotics and synbiotics play an important role in improving an athlete´s performance. These studies are currently limited in number and quality, hence it is necessary to improve the selection of functional biomarkers and methodological approaches, as well as determining the specific nutritional supplement and exercise doses.