Impact of Probiotics on the Performance of Endurance Athletes: A Systematic Review

ents contain different strains of living microorganisms that promote the health of the host. These dietary supplements are increasingly being used by athletes to improve different aspects such as athletic performance, upper respiratory tract infections (URTIs), the immune system, oxidative stress, gastrointestinal (GI) problems, etc. This study aimed to identify the current evidence on the management of probiotics in endurance athletes and their relationship with sports performance.

that promote the health of the host. These dietary supplements are increasingly being used by athletes to improve different aspects such as athletic performance, upper respiratory tract infections (URTIs), the immune system, oxidative stress, gastrointestinal (GI) problems, etc. This study aimed to identify the current evidence on the management of probiotics in endurance athletes and their relationship with sports performance. Methods: A systematic review of the last ve years was carried out in PubMed, Scopus, Web of science, Sportdiscus and Embase databases. Results:Nine articlesmet the quality criteria. Of these, three reported direct bene ts on sports performance. The remaining six articles found improvements in the reduction of oxidative stress, increased immune response and decreased incidence of URTIs. There is little scienti c evidence on the direct relationship between the administration of probiotics in endurance athletes and sports performance. Conclusions: Bene ts were found that probiotics could indirectly in uence sports performance by improving other parameters such as the immune system, response to URTIs and decreased oxidative stress, as well as the monitoring of scheduled workouts. Keywords:athletic; athletic performance; endurance training; probiotics; URTIs 1. Introduction The gut microbiota is a complex community of microorganisms that stably colonize the intestinal surface. It consists of 1014 resident microorganisms including bacteria, archaea, viruses and fungi. Mainly, the gut microbiota in healthy individuals is dominated by four groups: Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes [1–3]. Their functions are very diverse, ranging from fermenting, digesting and absorbing nutrients necessary to obtain energy and maintain the homeostasis of the organism, synthesis of vitamins and essential amino acids, modulation of the immune system and control of oxidative stress and in ammatory responses, to the maturation of the nervous system through the secretion of neuroactive molecules, etc. [4,5]. It is modulated by different environmental factors, being sensitive to physiological and homeostatic changes, which Int. J. Environ. Res. Public Health2021,18, 11576.

Int. J. Environ. Res. Public Health2021,18, 11576 2 of 12 can lead to alterations of the microbiota or dysbiosis. These factors include diet, stress, physical activity and exercise [6,7]. The relationship between gut microbiota and exercise is twofold, i.e., the micro- biota can be altered by exercise, especially endurance exercise, due to increased oxidative stress [8], intestinal permeability, electrolyte imbalance, glycogen depletion, etc. [9]. In addition, the microbiota in uences the individual's ability to perform optimally during exercise due to its ability to take up energy, modulate the immune system, regulate GI health [10] and reverse the in ammatory response after exercise [11,12]. In recent years, there has been an increase in attendance at endurance sporting events such as marathons, ultramarathons, triathlons, cycling events, etc. This has led to an increase in the competitiveness of these events, as well as an increase in the active search for ergogenic aids by athletes with the aim of improving their sporting performance. Some elite athletes take a diet low in plant ber to slow gastric emptying and reduce intestinal problems during exercise, but this recommendation can lead to a decrease in the diversity and functionality of the intestinal microbiota [5,13]. Therefore, alternatives such as the use of probiotics have been studied. Probiotics are living microorganisms that have health bene ts when consumed in adequate amounts [14]. Recently, the use of these microorganisms in sport, to reduce the in ammatory response and episodes of gastroenteritis and URTIs among athletes, has increased [1,15]. This health improvement in athletes is expected to positively in uence their physical performance [8]. One of the strongest lines of research in this eld, among elite athletes, is the veri - cation of how physical exercise, in general, modi es the microbiota. According to data reported by Scheiman, Veillonella causes an increase of 13% in endurance performance, due to a metabolic advantage by the colonization of lactate metabolizing organisms, transform- ing it into propionate. Therefore, this nding is very promising, currently investigating the creation of probiotic capsules composed of Veillonella to increase the population of this bacterium in the intestinal microbiota

microbiota. According to data reported by Scheiman, Veillonella causes an increase of 13% in endurance performance, due to a metabolic advantage by the colonization of lactate metabolizing organisms, transform- ing it into propionate. Therefore, this nding is very promising, currently investigating the creation of probiotic capsules composed of Veillonella to increase the population of this bacterium in the intestinal microbiota of athletes and thus improve their performance. Re- search is also being carried out in which fecal transplants from athletes with an abundance of this bacterium to other athletes is carried out to see if they promote the proliferation of these bacteria, and thus increase athletic performance [16]. In addition, it has been proven that the combination of probiotics and a diet rich in ber reduces recovery days after intense periods of training, contributing to good performance [17] and avoiding the immunological effects of URTIs, and improving GI problems, psychological problems, oxidative stress, etc. of overtraining [18] and with it, sports performance. The recommendation to use probiotics in these athletes must be backed by evidence, as no systematic review or meta-analysis has been found that assesses the quality or scienti c rigor of the studies carried out to date. Therefore, the aim of this review was to identify, following a systematic methodology, the current evidence on the management of probiotics in endurance athletes and their relationship with sports performance. 2. Materials and Methods A systematic review of the literature was conducted. The results were obtained by direct online access through the following databases: PubMed, Web of Science (WOS), Sco- pus, Sportdiscus and Embase. The aim of this review was to address the following question: Does probiotic supplementation improve sports performance in endurance athletes? To de ne the research question, the PICOS criteria (Table) were used. We studied articles published in any country, by any institution or individual re- searcher, written in Spanish and English. These articles had to be accessible in full text through Open Access. The search was limited to articles published in the last ve years (2016–2020).

PICOS criteria (Table) were used. We studied articles published in any country, by any institution or individual re- searcher, written in Spanish and English. These articles had to be accessible in full text through Open Access. The search was limited to articles published in the last ve years (2016–2020).

Int. J. Environ. Res. Public Health2021,18, 11576 3 of 12 Table 1.PICOS criteria (Population; Intervention; Comparison; Outcome; Study design). P Endurance Athletes I Probiotic supplementation C No supplementation O Improved sporting performance S Systematic review The associated MeSH descriptors “endurance training”, “athletic performance”, “pro- biotics” and “prebiotics” were used for document retrieval. No subject classi ers (Subhead- ings) or Entry Terms were used. The search strategies used were as follows: “endurance training” AND “probiotics”; “athletic performance” AND “probiotics”; (“endurance train- ing” OR “athletic performance”) AND “probiotics”; (“endurance training” OR “athletic performance”) AND “probiotics” NOT prebiotics. The nal selection of articles was made according to the following inclusion criteria: (a) studies published in journals indexed in international databases that were subjected to peer review, (b) access to the full text, (c) in humans and (d) written in English and Spanish; and exclusion criteria: (a) studies not based on the target population, (b) expert reports, letters from the editor, books, monographs, clinical narratives or systematic reviews or meta-analyses. Due to the large number of articles found in the rst search and as an assessment of quality, two sieving processes were carried out. The rst one was based on the title and abstract, eliminating studies that were not on the topic of interest and whose populations were not endurance athletes. For the second screening, we used the quality questionnaire validated by Castro-Piñero and colleagues in 2009 [19]. 3. Results A total of 26 published articles were located, 8 (30.77%) PubMed, 1 (3.85%) Scopus, 2 (7.69%) Sportdiscus, 7 (26.92%) Web of Science and 8 (30.77%) Embase. Of these retrieved papers, 11 of them were redundant (42.31%). Once the rst screening was applied based on the title and abstract and compliance with the inclusion and exclusion criteria, 10 articles were selected. After assessing the quality of these papers using the quality questionnaire validated by Ruiz et al. in 2009, the 9 articles written in English were retained (Figure). The results obtained showed different study parameters in the approach to the pro- posed topic (Table). Table 2. Characteristics and main results of clinical trials on the

exclusion criteria, 10 articles were selected. After assessing the quality of these papers using the quality questionnaire validated by Ruiz et al. in 2009, the 9 articles written in English were retained (Figure). The results obtained showed different study parameters in the approach to the pro- posed topic (Table). Table 2. Characteristics and main results of clinical trials on the use of probiotics in endurance athletes and improvement of sports performance. Author, Year Type of Study/Quality Supplementation Procedure Results Conclusions Batattinha et al., 2020 [20]. Double-blind, placebo-controlled RCT in 27 marathon runners (men) High quality = 5 N = 11–50 1 sachet ofBi dobacterium- animalis-subs p.-Lactis (10 10 9 CFU)and Lactobacillus-Acidophilus (10 10 9 CFU) + 5 g maltodextrin for 30 days before the race. The total number of CD8 T lymphocytes was maintained in the probiotic group and the production of proin ammatory cytokines decreased, enhancing the immunomodulatory role of lymphocytes. There were no differences between the two groups in relation to URTIs. The probiotic group modulates the lymphocyte response.

Int. J. Environ. Res. Public Health2021,18, 11576 4 of 12 Table 2.Cont. Author, Year Type of Study/Quality Supplementation Procedure Results Conclusions Huang et al. 2020 [21] Double-blind, placebo-controlled RCT in 20 triathletes (male) High quality = 5 N = 11–50. 1 capful of Lactobacillusplantarum PS128(1.5 10 10 CFU) for 4 weeks. Increased endurance in the probiotic group. There were no signi cant differences in VO2max and body composition in the two groups. LPS128 supplementation was associated with an improvement in endurance running performance through modulation of microbiota and related metabolites, but not in maximal oxygen uptake. Lin et al. 2020 [22] Double-blind, placebo-controlled RCT in 21 middle- and long-distance runners (7 women and 14 men) High quality = 5 N = 11–50 3 capsules/day for 5 weeks ofBi dobacterium longum subsp. longum Olympic No. 1 (OLP-01)(15 10 10 CFU) after meals. The OLP-01 group signi cantly increased the change in running distance of the 12-min Cooper test, with an increase in bene cial bacteria and decrease in pathogenic bacteria in the gut microbiota. OLP-01 can be used as a sports nutrition supplement to enhance exercise performance. Huang et al. 2019 [23] Double-blind, placebo-controlled RCT in 34 triathletes. It was divided into study I (18 triathletes) and study II (16 triathletes). High quality = 5 N = 11–50 Study I, programmed training (triathlon preparation) and supplementation with Lactobacillus plantarum PS128lasting 4 weeks. Study II, specialized training and supplementation with Lactobcillusplantarum PS128 lasting 3 weeks and dietary recommendations (30–40 g of carbohydrates and 500–1000 mL of water/hour) during the triathlon. Decrease in oxidative stress due to 6–13% decrease in proin ammatory cytokines and 55% increase in anti-in ammatory cytokines, after intense exercise. 24–69% increase in plasma amino acids and athletic performance in the probiotic group, due to improved fatigue index (FI) and maximal anaerobic power (PP). Supplementation with Lactobacillus plantarum PS128may be a potential ergogenic aid for better training management, physiological adaptations to exercise and health promotion. Marshall et al. 2017 [24] Double-blind RCT in 32 ultramarathoners (6 women and 26 men) High quality = 5 N = 11–50 Probiotic group (n=

the probiotic group, due to improved fatigue index (FI) and maximal anaerobic power (PP). Supplementation with Lactobacillus plantarum PS128may be a potential ergogenic aid for better training management, physiological adaptations to exercise and health promotion. Marshall et al. 2017 [24] Double-blind RCT in 32 ultramarathoners (6 women and 26 men) High quality = 5 N = 11–50 Probiotic group (n= 11): 150 g/day ofLactobacillus acidophilus,bi dobacterium bi dumandbi dobacterium aniamles subspecies lactis. Probiotic + glutamine group (n= 10): 0.9 g L-glutamine per 5 g dosage. No supplementation (n= 11). Follow-up during the 12 weeks prior to the Sabre Marathon. After the run, eHsp72 concentrations increased by 124% (F [1,3] = 22.716, p< 0.001), indicating increased levels of systemic stress. There was no difference between groups in eHsp72 concentration. Supplementation with probiotics or probiotics + glutamine did not decrease the concentration of eHsp72, an indicator of systemic stress after an ultramarathon.

Int. J. Environ. Res. Public Health2021,18, 11576 5 of 12 Table 2.Cont. Author, Year Type of Study/Quality Supplementation Procedure Results Conclusions Strasser et al. 2016 [25]. Double-blind RCT in 29 ultramarathoners (16 women and 13 men) High quality = 5 N = 11–50 1 sachet before breakfast (1 10 10 CFU of Bi dobacterium bi dum W23, Bi dobacterium lactis W51, Enterococcus faecium W54, Lactobacillus acidophilus W22, Lactobacillus brevis W63, andLactococcus lactis W58), for 12 weeks. Tryptophan levels after exercise remained unchanged in the probiotic group. The proportion of placebo who suffered 1 or 2 symptoms of URTIs increased 2.2-fold compared to the probiotic group (0.79 vs. 0.35;p=0.02). Daily probiotic supplementation decreased the rate of exercise-induced tryptophan degradation and reduced the incidence of URTIs, but did not bene t athletic performance, although training load was higher (h/week). Jager et al. 2016 [26]. Double-blind RCT in 15 endurance runners (male) High quality = 5 N = 11–50 1 capsule/day of Bi dobacterium breve BR03 andStreptococcus thermophilus FP4 (5 10 9 CFU) for 3 weeks. Probiotic supplementation decreased circulating IL-6 up to 48 h after exercise. It improved the average peak torque in an isometric test at 24 and 72 h. Probiotic intake mitigates performance reductions and muscle tension in the days after exercise, which damages muscles. Speci c dietary probiotics can aid in performance recovery after heavy eccentric exercise, which in uences the performance of endurance runners. Jager et al. 2016 [27] Double-blind RCT in 20 endurance runners (male) High quality = 5 N = 11–50 Cross-over study: Week 0–2, supplementation with 20 gr of casein after breakfast. Week 4–6, supplementation withBacillus coagulans GBI-30, 6086 + 20 gr casein after breakfast. Probiotic + casein supplementation increased recovery at 24 and 72 h and decreased pain at 72 h, with an increase in creatine kinase (CK) of +137.7% (p= 0.001) versus casein group, which was +266.8% (p= 0.0002). In addition, muscle damage decreased (p= 0.08). Intense exercise maintained athletic performance (+10.1 watts + 1.7%). Probiotic + casein supplementation decreased muscle damage levels, increased recovery and maintained performance after damaging exercise. Gleeson et

h and decreased pain at 72 h, with an increase in creatine kinase (CK) of +137.7% (p= 0.001) versus casein group, which was +266.8% (p= 0.0002). In addition, muscle damage decreased (p= 0.08). Intense exercise maintained athletic performance (+10.1 watts + 1.7%). Probiotic + casein supplementation decreased muscle damage levels, increased recovery and maintained performance after damaging exercise. Gleeson et al. 2016 [28]. Double-blind, placebo-controlled RCT in 243 collegiate athletes (women and men) High quality = 6 2 drinks/day (breakfast and dinner) ofLactobacillus casei shirota(6.5 10 9 CFU) for 20 weeks. There were no signi cant differences in duration and severity of URTIs between groups. Signi cant interaction effect between times and groups against CMV 10 and EBV 10 antibodies in plasma (p< 0.01), in the probiotic group. Probiotic supplementation did not decrease the incidence of URTIs, but decreased EBV and CMV antibodies. RCT: randomized clinical trial; CFU: colony-forming units; URTIs: upper respiratory tract infections; VO2max: peak oxygen volume; EBV: Epstein–Barr virus; CMV: cytomegalovirus. All the selected articles were double-blind randomized clinical trials (RCTs). The sample size in 8 of the 9 articles was below 50 subjects, and only one had 243 participants. Of the total number of publications, only four took both sexes as the sample. The remaining 5 only selected men.

Int. J. Environ. Res. Public Health2021,18, 11576 6 of 12Int. J. Environ. Res. Public Health 2021, 18, x 4 of 13 Figure 1. PRISMA (Preferred Reporting Items for Systematic Review and Meta‐Analyses) diagram. The results obtained showed different study parameters in the approach to the proposed topic (Table 2). Table 2. Characteristics and main results of clinical trials on the use of probiotics in endurance athletes and improvement of sports performance. Author, Year Type of Study/Quality Supplementation Procedure Results Conclusions Batattinha et al., 2020 [20]. Double‐blind, placebo‐controlle d RCT in 27 marathon runners (men) High quality = 5 N = 11–50 1 sachet of Bifidobacte‐ rium‐animalis‐subs p.‐Lactis (10 × 10 9 CFU) and Lactoba‐ cillus‐Acidophilus (10 × 10 9 CFU) + 5 g maltodextrin for 30 days before the race. The total number of CD8 T lymphocytes was maintained in the probiotic group and the production of proinflammatory cytokines decreased, enhancing the immunomodulatory role of lymphocytes. There were no differences between the two groups in relation to URTIs. The probiotic group modulates the lymphocyte response. Huang et al. 2020 [21] Double‐blind, placebo‐controlle d RCT in 20 1 capful of Lactobacil‐ lusplantarum PS128 (1.5 × 10 10 CFU) for 4 weeks. Increased endurance in the probiotic group. There were no significant LPS128 supplementation was associated with an improvement in endurance Figure 1.PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) diagram. Regarding the probiotics selected, only 2 used Lactobacillus plantarum P128[21,23] . The rest were different strains such as Bi dobacterium animalis subsp. Lactis (10 10 9 ) and Lactobacillus-Acidophilus (10 10 9 ) [20], Bi dobacterium bi dum (W23), Bi dobacterium lactis (W51), Enterococcus faecium (W54), Lactobacillus acidophilus (W22), Lactobacillus brevis (W63) and Lactococcus lactis (W58) [25], Bi dobacterium longum subsp. longum Olympic No. 1 (OLP-01) [22], Bi dobacterium (B.) breve BR03 Streptococcus (S.) ther- mophilus FP4 at 5 bn live cell count (CFU) [26] and Lactobacillus casei Shirota (LcS) [28]. Two of the total articles used as intervention a combination of probiotics (Lactobacillus acidophilus, bi dobacterium bi dum and bi dobacteriumanimalis subsp. lactis) and the same probiotic + glutamine

A systematic review assessing the impact of probiotics on endurance athletes' performance.