Supplementation of Probiotics and Its Effects on Physically Active Individuals and Athletes: Systematic Review

A systematic scoping review of study methodology for randomized controlled trials investigating probiotics in athletic and physically active populations

BACKGROUND

The purported ergogenic and health effects of probiotics have been a topic of great intrigue among researchers, practitioners, and the lay public alike. There has also been an increased research focus within the realm of sports science and exercise medicine on the athletic gut microbiota. However, compared to other ergogenic aids and dietary supplements, probiotics present unique study challenges. The objectives of this systematic scoping review were to identify and characterize study methodologies of randomized controlled trials investigating supplementation with probiotics in athletes and physically active individuals.

METHODS

Four databases (MEDLINE, CINAHL, Cochrane CENTRAL, and Cochrane Database of Systematic Reviews) were searched for randomized controlled studies involving healthy athletes or physically active individuals. An intervention with probiotics and inclusion of a control and/or placebo group were essential. Only peer-reviewed articles in English were considered, and there were no date restrictions. Results were extracted and presented in tabular form to detail study protocols, characteristics, and outcomes. Bias in randomized controlled trials was determined with the RoB 2.0 tool.

RESULTS

A total of 45 studies were included in the review, with 35 using a parallel group design and 10 using a cross-over design. Approximately half the studies used a single probiotic and the other half a multi-strain preparation. The probiotic dose ranged from 2 × 108 to 1 × 1011 colony forming units daily, and the length of intervention was between 7 and 150 days. Fewer than half the studies directly assessed gastrointestinal symptoms, gut permeability, or the gut microbiota. The sex ratio of participants was heavily weighted toward males, and only 3 studies exclusively investigated females. Low-level adverse events were reported in only 2 studies, although the methodology of reporting varied widely. The risk of bias was generally low, although details on randomization were lacking in some studies.

CONCLUSION

There is a substantial body of research on the effects of probiotic supplementation in healthy athletes and physically active individuals. Considerable heterogeneity in probiotic selection and dosage as well as outcome measures has made clinical and mechanistic interpretation challenging for both health care practitioners and researchers. Attention to issues of randomization of participants, treatments and interventions, selection of outcomes, demographics, and reporting of adverse events will facilitate more trustworthy interpretation of probiotic study results and inform evidence-based guidelines.

Effect of Probiotic Supplementation on Gut Microbiota and Sport Performance in Athletes and Physically Active Individuals: A Systematic Review

The present systematic review aimed to evaluate the effect of probiotic supplementation on gut microbiota and sport performance in athletes and physically active individuals. This review followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (P RISMA). The search had no time limits and included the following databases: MEDLINE, LILACS, Scopus, Web of Science, Cochrane, and SP ORT Discus. The risk of bias was assessed through the updated version of the Cochrane tool for assessing the risk of bias in randomized trials (RoB 2). Nine randomized clinical trials (RCTs) were included, accounting for 216 participants. Of these, seven studies found positive results on sport performance. Additionally, some studies showed significant decrease in biochemical parameters linked to inflammation. It was also observed direct results in the microbiota composition of the participants, such as an increase in the abundance of probiotics and a decrease in certain pathogenic bacteria. Therefore, the use of probiotics showed improvement in inflammatory biomarkers and oxidative stress, which indirectly may contribute to the improvement of sport performance. However, the majority of the studies presented a high risk of bias, which impair the reproducibility of the results. While the field of probiotic supplementation and sport performance is emerging, the promising results from this systematic review suggest that further investigation through larger and more robust randomized clinical trials can provide valuable insights for athletes and their performance.

Effects of probiotic supplementation on performance of resistance and aerobic exercises: a systematic review

CONTEXT

Strenuous exercise may lead to negative acute physiological effects that can impair athletic performance. Some recent studies suggest that probiotic supplementation can curtail these effects by reducing the permeability of the intestinal barrier, yet results are inconsistent.

OBJECTIVE

The aim of this systematic review is to assess the effects of probiotic supplementation on athletic performance.

DATA SOURCES

The PubMed/MEDLINE, Cochrane, and Scopus databases were searched for articles that assessed the effects of probiotic supplementation on athletic performance.

DATA EXTRACTION THIS SYSTEMATIC REVIEW IS REPORTED ACCORDING TO

PRISMA guidelines. Risk of bias was assessed through the Cochrane RoB 2.0 tool. Seventeen randomized clinical trials assessing athletic performance as the primary outcome were included. In total, 496 individuals (73% male) comprising athletes, recreationally trained individuals, and untrained healthy individuals aged 18 to 40 years were investigated.

DATA ANALYSIS

Three studies showed an increase or an attenuation of aerobic performance (decline in time to exhaustion on the treadmill) after supplementation with probiotics, while 3 found an increase in strength. However, most studies (n = 11) showed no effect of probiotic consumption on aerobic performance (n = 9) or muscular strength (n = 2). The most frequently used strain was Lactobacillus acidophilus, used in 2 studies that observed positive results on performance. Studies that used Lactobacillus plantarum TK10 and Lactobacillus plantarum PS128 also demonstrated positive effects on aerobic performance and strength, but they had high risk of bias, which implies low confidence about the actual effect of treatment.

CONCLUSION

There is not enough evidence to support the hypothesis that probiotics can improve performance in resistance and aerobic exercises. Further well-controlled studies are warranted.

Orally Ingested Probiotics, Prebiotics, and Synbiotics as Countermeasures for Respiratory Tract Infections in Nonelderly Adults: A Systematic Review and Meta-Analysis

The impact of gut microbiota-targeted interventions on the incidence, duration, and severity of respiratory tract infections (RTIs) in nonelderly adults, and factors moderating any such effects, are unclear. This systematic review and meta-analysis aimed to determine the effects of orally ingested probiotics, prebiotics, and synbiotics compared with placebo on RTI incidence, duration, and severity in nonelderly adults, and to identify potential sources of heterogeneity. Studies were identified by searching CENTRAL, PubMed, Scopus, and Web of Science up to December 2021. English-language, peer-reviewed publications of randomized, placebo-controlled studies that tested an orally ingested probiotic, prebiotic, or synbiotic intervention of any dose for ≥1 wk in adults aged 18-65 y were included. Results were synthesized using intention-to-treat and per-protocol random-effects meta-analysis. Heterogeneity was explored by subgroup meta-analysis and meta-regression. Risk of bias was assessed using the Cochrane risk-of-bias assessment tool for randomized trials version 2 (RoB2). Forty-two manuscripts reporting effects of probiotics (n = 38), prebiotics (n = 2), synbiotics (n = 1) or multiple -biotic types (n = 1) were identified (n = 9179 subjects). Probiotics reduced the risk of experiencing ≥1 RTI (relative risk = 0.91; 95% CI: 0.84, 0.98; P = 0.01), and total days (rate ratio = 0.77; 95% CI: 0.71, 0.83; P < 0.001), duration (Hedges' g = -0.23; 95% CI: -0.39, -0.08; P = 0.004), and severity (Hedges' g = -0.16; 95% CI: -0.29, -0.03; P = 0.02) of RTIs. Effects were relatively consistent across different strain combinations, doses, and durations, although reductions in RTI duration were larger with fermented dairy as the delivery matrix, and beneficial effects of probiotics were not observed in physically active populations. Overall risk of bias was rated as "some  concerns" for most studies. In conclusion, orally ingested probiotics, relative to placebo, modestly reduce the incidence, duration, and severity of RTIs in nonelderly adults. Physical activity and delivery matrix may moderate some of these effects. Whether prebiotic and synbiotic interventions confer similar protection remains unclear due to few relevant studies. This trial was registered at https://www.crd.york.ac.uk/prospero/ as CRD42020220213.

Effect of prebiotics, probiotics, and synbiotics on gastrointestinal outcomes in healthy adults and active adults at rest and in response to exercise-A systematic literature review

Introduction

A systematic literature search was undertaken to assess the impact of pre-, pro-, and syn-biotic supplementation on measures of gastrointestinal status at rest and in response to acute exercise.

Methods

Six databases (Ovid MEDLINE, EMBASE, Cinahl, SportsDISCUS, Web of Science, and Scopus) were used. Included were human research studies in healthy sedentary adults, and healthy active adults, involving supplementation and control or placebo groups. Sedentary individuals with non-communicable disease risk or established gastrointestinal inflammatory or functional diseases/disorders were excluded.

Results

A total of n = 1,204 participants were included from n = 37 papers reported resting outcomes, and n = 13 reported exercise-induced gastrointestinal syndrome (EIGS) outcomes. No supplement improved gastrointestinal permeability or gastrointestinal symptoms (GIS), and systemic endotoxemia at rest. Only modest positive changes in inflammatory cytokine profiles were observed in n = 3/15 studies at rest. Prebiotic studies (n = 4/5) reported significantly increased resting fecal Bifidobacteria, but no consistent differences in other microbes. Probiotic studies (n = 4/9) increased the supplemented bacterial species-strain. Only arabinoxylan oligosaccharide supplementation increased total fecal short chain fatty acid (SCFA) and butyrate concentrations. In response to exercise, probiotics did not substantially influence epithelial injury and permeability, systemic endotoxin profile, or GIS. Two studies reported reduced systemic inflammatory cytokine responses to exercise. Probiotic supplementation did not substantially influence GIS during exercise.

Discussion

Synbiotic outcomes resembled probiotics, likely due to the minimal dose of prebiotic included. Methodological issues and high risk of bias were identified in several studies, using the Cochrane Risk of Bias Assessment Tool. A major limitation in the majority of included studies was the lack of a comprehensive approach of well-validated biomarkers specific to gastrointestinal outcomes and many included studies featured small sample sizes. Prebiotic supplementation can influence gut microbial composition and SCFA concentration; whereas probiotics increase the supplemented species-strain, with minimal effect on SCFA, and no effect on any other gastrointestinal status marker at rest. Probiotic and synbiotic supplementation does not substantially reduce epithelial injury and permeability, systemic endotoxin and inflammatory cytokine profiles, or GIS in response to acute exercise.

Impact of probiotic supplementation on exercise endurance among non-elite athletes: study protocol for a randomized, placebo-controlled, double-blind, clinical trial

Background

Some probiotics appear to improve athletic performance, endurance, and recovery after intense exercise. Other formulations may provide performance-related benefits via immune and gastrointestinal functions in athletic individuals. However, few formulations have been studied for both types of effects among non-elite athletes. The primary objective of this study is to assess the ergogenic effects of a probiotic on high-intensity endurance running performance in non-elite runners. Secondary objectives include assessment of perceived exertion, blood chemistry, immune and stress biomarkers, cold and flu symptoms, and gastrointestinal health after the probiotic intervention.

Methods

This 9-week randomized, placebo-controlled, double-blind, parallel trial will assess the ergogenic effects of a probiotic (5 billion colony-forming units/day, for 6 weeks) in healthy, non-elite runners (N=32; 18–45 years). Participants will be monitored via daily and weekly questionnaires during the 2-week pre-baseline, 6-week intervention, and 1-week washout. Questionnaires will inquire about activity, muscle soreness, gastrointestinal symptoms, cold and flu symptoms, stool form and frequency, and adverse events. During the pre-baseline visit, maximal oxygen uptake (V̇O₂ max) is assessed to set appropriate individualized workload settings for the treadmill time-to-exhaustion endurance tests. These time-to-exhaustion endurance running tests will be completed at an intensity of 85% VO₂max at baseline and final visits. During these tests, self-perceived exercise effort will be rated via the Borg Rating of Perceived Exertion scale and finger sticks assessing capillary blood glucose and lactate concentrations will be collected every 3 min. Additional questionnaires will assess diet and motivation to exercise. Body composition will be assessed using air displacement plethysmography at the baseline and final visits. Hypotheses will be tested using two-sided tests, and a linear model and with a type I error rate of α=0.05. Primary and secondary outcomes will be tested by comparing results between the intervention groups, adjusting for baseline values.

Discussion

These results will build evidence documenting the role of probiotics on running endurance performance and physiological responses to exercise in non-elite athletes. Understanding the potential mechanisms of probiotic effects and how they mitigate the intestinal or immune discomforts caused by running could provide additional strategy means to help runners improve their performance.

Trial registration number

ClinicalTrials.govNCT04588142. Posted on October 19, 2020.

Protocol version: July 2, 2021, version 1.2

PROBIOTIC SUPPLEMENTS FOR ENDURANCE EXERCISE PERFORMANCE AND IMMUNE FUNCTION

ABSTRACT Introduction: After long-term research, it was found that athletes are susceptible to suffering from upper respiratory tract infections and digestive system diseases when subjected to high-intensity exercise for long periods. Objective: To verify whether consuming probiotic supplements after exercise can significantly improve the function of the immune system and play a positive role in the health of athletes. Method: This is a quantitative study with distribution analysis to verify whether probiotic supplements could improve immune response after exercise. Results: After using probiotic supplements, by recording the individual differences in the distribution characteristics of athletes› gastrointestinal flora, we found that the changes of subjects› sports performance, leukocytes, neutrophils, lymphocytes, and gastrointestinal flora after six weeks of special training were different. Conclusion: Long-term oral probiotics for athletes can effectively reduce inflammation in the body, reduce damage to the body during exercise, and effectively improve the gastrointestinal tract›s immune function. Level of evidence II; Therapeutic studies - investigation of treatment results.

Effect of fermented milk on upper respiratory tract infection in adults who lived in the haze area of Northern China: a randomized clinical trial

CONTEXT

Upper respiratory tract infection (URTI) is the most common illness in humans. Fermented milk containing probiotics can mitigate URTI symptoms.

OBJECTIVE

This study tests the effect of fermented milk (Qingrun), a yogurt supplemented with Bifidobacterium animalis subsp. lactis Bl-04, on adults with URTIs who live in a haze-covered area in a randomized clinical trial.

MATERIALS AND METHODS

A total of 136 subjects were enrolled in the study at the baseline and randomized to consume either control yogurt or Qingrun yogurt (250 g) once daily for 12 weeks. The duration and severity of URTI were evaluated by the Wisconsin Upper Respiratory Symptom Survey-24. Blood and faecal samples were collected at the baseline and post-intervention, to determine the changes of immune biomarkers.

RESULTS

Qingrun yogurt significantly reduced the incidence of the common cold (OR, 0.38; 95% CI, 0.17-0.81; p = 0.013) and influenza-like illness (OR, 0.32; 95% CI, 0.11-0.97; p = 0.045). Compared to the control yogurt, Qingrun yogurt significantly reduced the duration (1.23 ± 2.73 vs. 4.78 ± 5.09 d) and severity score (3.58 ± 7.12 vs. 11.37 ± 11.73) of URTI. In addition, the post-intervention levels of interferon-γ (139.49 ± 59.49 vs. 113.45 ± 65.12 pg/mL) and secretory immunoglobulin A (529.19 ± 91.70 vs. 388.88 ± 53.83 mg/dL) significantly increased in the Qingrun group, compared with those in the control group.

CONCLUSIONS

Qingrun yogurt showed a protective effect against URTI in adults, suggesting that the use of yogurt with probiotics could be a promising dietary supplement for mitigating URTI.

Fueling Gut Microbes: A Review of the Interaction between Diet, Exercise, and the Gut Microbiota in Athletes

The athlete's goal is to optimize their performance. Towards this end, nutrition has been used to improve the health of athletes' brains, bones, muscles, and cardiovascular system. However, recent research suggests that the gut and its resident microbiota may also play a role in athlete health and performance. Therefore, athletes should consider dietary strategies in the context of their potential effects on the gut microbiota, including the impact of sports-centric dietary strategies (e.g., protein supplements, carbohydrate loading) on the gut microbiota as well as the effects of gut-centric dietary strategies (e.g., probiotics, prebiotics) on performance. This review provides an overview of the interaction between diet, exercise, and the gut microbiota, focusing on dietary strategies that may impact both the gut microbiota and athletic performance. Current evidence suggests that the gut microbiota could, in theory, contribute to the effects of dietary intake on athletic performance by influencing microbial metabolite production, gastrointestinal physiology, and immune modulation. Common dietary strategies such as high protein and simple carbohydrate intake, low fiber intake, and food avoidance may adversely impact the gut microbiota and, in turn, performance. Conversely, intake of adequate dietary fiber, a variety of protein sources, and emphasis on unsaturated fats, especially omega-3 (ɷ-3) fatty acids, in addition to consumption of prebiotics, probiotics, and synbiotics, have shown promising results in optimizing athlete health and performance. Ultimately, while this is an emerging and promising area of research, more studies are needed that incorporate, control, and manipulate all 3 of these elements (i.e., diet, exercise, and gut microbiome) to provide recommendations for athletes on how to "fuel their microbes."

Sport supplements and the athlete's gut: a review

Vigorous or prolonged exercise poses a challenge to gastrointestinal system functioning and is associated with digestive symptoms. This narrative review addresses 1) the potential of dietary supplements to enhance gut function and reduce exercise-associated gastrointestinal symptoms and 2) strategies for reducing gastrointestinal-related side effects resulting from popular sports supplements. Several supplements, including probiotics, glutamine, and bovine colostrum, have been shown to reduce markers of gastrointestinal damage and permeability with exercise. Yet, the clinical ramifications of these findings are uncertain, as improvements in symptoms have not been consistently observed. Among these supplements, probiotics modestly reduced exercise-associated gastrointestinal symptoms in a few studies, suggesting they are the most evidenced-based choice for athletes looking to manage such symptoms through supplementation. Carbohydrate, caffeine, and sodium bicarbonate are evidence-based supplements that can trigger gastrointestinal symptoms. Using glucose-fructose mixtures is beneficial when carbohydrate ingestion is high (>50 g/h) during exercise, and undertaking multiple gut training sessions prior to competition may also be helpful. Approaches for preventing caffeine-induced gastrointestinal disturbances include using low-to-moderate doses (<500 mg) and avoiding/minimizing exacerbating factors (stress, anxiety, other stimulants, fasting). Adverse gastrointestinal effects of sodium bicarbonate can be avoided by using enteric-coated formulations, low doses (0.2 g/kg), or multi-day loading protocols.

Gastrointestinal Assessment and Therapeutic Intervention for the Management of Exercise-Associated Gastrointestinal Symptoms: A Case Series Translational and Professional Practice Approach

This translational research case series describes the implementation of a gastrointestinal assessment protocol during exercise (GastroAxEx) to inform individualised therapeutic intervention of endurance athletes affected by exercise-induced gastrointestinal syndrome (EIGS) and associated gastrointestinal symptoms (GIS). A four-phase approach was applied. Phase 1: Clinical assessment and exploring background history of exercise-associated gastrointestinal symptoms. Phase 2: Individual tailored GastroAxEx laboratory simulation designed to mirror exercise stress, highlighted in phase 1, that promotes EIGS and GIS during exercise. Phase 3: Individually programmed therapeutic intervention, based on the outcomes of Phase 2. Phase 4: Monitoring and readjustment of intervention based on outcomes from field testing under training and race conditions. Nine endurance athletes presenting with EIGS, and two control athletes not presenting with EIGS, completed Phase 2. Two athletes experienced significant thermoregulatory strain (peak core temperature attained > 40°C) during the GastroAxEx. Plasma cortisol increased substantially pre- to post-exercise in n = 6/7 (Δ > 500 nmol/L). Plasma I-FABP concentration increased substantially pre- to post-exercise in n = 2/8 (Δ > 1,000 pg/ml). No substantial change was observed in pre- to post-exercise for systemic endotoxin and inflammatory profiles in all athletes. Breath H2 responses showed that orocecal transit time (OCTT) was delayed in n = 5/9 (90-150 min post-exercise) athletes, with the remaining athletes (n = 4/9) showing no H2 turning point by 180 min post-exercise. Severe GIS during exercise was experienced in n = 5/9 athletes, of which n = 2/9 had to dramatically reduce work output or cease exercise. Based on each athlete's identified proposed causal factors of EIGS and GIS during exercise (i.e., n = 9/9 neuroendocrine-gastrointestinal pathway of EIGS), an individualised gastrointestinal therapeutic intervention was programmed and advised, adjusted from a standard EIGS prevention and management template that included established strategies with evidence of attenuating EIGS primary causal pathways, exacerbation factors, and GIS during exercise. All participants reported qualitative data on their progress, which included their previously presenting GIS during exercise, such as nausea and vomiting, either being eliminated or diminished resulting in work output improving (i.e., completing competition and/or not slowing down during training or competition as a result of GIS during exercise). These outcomes suggest GIS during exercise in endurance athletes are predominantly related to gastrointestinal functional and feeding tolerance issues, and not necessarily gastrointestinal integrity and/or systemic issues. GastroAxEx allows for informed identification of potential causal pathway(s) and exacerbation factor(s) of EIGS and GIS during exercise at an individual level, providing a valuable informed individualised therapeutic intervention approach.

Effect of Probiotic Consumption on Immune Response in Athletes: A Meta-analysis

The possible effect of probiotic interventions on immunological markers in athletes is inconclusive. Therefore, to synthesize and quantitatively analyze the existing evidence on this topic, systematic literature searches of online databases PubMed, Scopus, Cochrane Library, and ISI Web of Sciences was carried out up to February 2021 to find all randomized controlled trials (RCTs) concerning the immunological effects of probiotics in athletes. In the random-effects model, weighted mean difference (WMD) and 95% confidence interval (CI) explained the net effect. The authors assessed the likelihood of publication bias via Egger's and Begg's statistics. A total of 13 RCTs (836 participants) were retrieved. Probiotic consumption reduced lymphocyte T cytotoxic count significantly (WMD=-0.08 cells×10⁹/L; 95% CI: -0.15 to -0.01; p=0.022) with evidence of moderate heterogeneity (I ²⁼59.1%, p=0.044) and monocyte count when intervention duration was ≤ 4 weeks (WMD=-0.08 cells×10⁹/L; 95% CI: -0.16 to -0.001; I ²⁼0.0%). Furthermore, leukocyte count was significantly elevated (WMD=0.48 cells×10⁹/L; 95% CI: 0.02 to 0.93; I ²⁼0.0%) when multi-strain probiotics were used. Probiotic supplements may improve immunological markers, including lymphocyte T cytotoxic, monocyte, and leukocyte in athletes. Further randomized controlled trials using diverse strains of probiotics and consistent outcome measures are necessary to allow for evidence-based recommendations.

Gut Microbiota-targeted Interventions for Reducing the Incidence, Duration, and Severity of Respiratory Tract Infections in Healthy Non-elderly Adults

INTRODUCTION

Respiratory tract infections (RTI), such as those caused by influenza viruses and, more recently, the severe acute respiratory syndrome coronavirus-2, pose a significant burden to military health care systems and force readiness. The gut microbiota influences immune function, is malleable, and may provide a target for interventions aiming to reduce RTI burden. This narrative review summarizes existing evidence regarding the effectiveness of probiotics, prebiotics, and synbiotics, all of which are gut microbiota-targeted interventions, for reducing the burden of RTI in military-relevant populations (i.e., healthy non-elderly adults).

MATERIALS AND METHODS

A systematic search strategy was used to identify recent meta-analyses and systematic reviews of randomized controlled trials conducted in healthy non-elderly adults which examined effects of probiotics, prebiotics, or synbiotics on the incidence, duration, and/or severity of RTI, or on immune responses to vaccinations against viruses that cause RTI. Relevant randomized controlled clinical trials not included in those reports were also identified.

RESULTS

Meta-analyses and multiple randomized controlled trials have demonstrated that certain probiotic strains may reduce the incidence, duration, and/or severity of RTI and improve immune responses to vaccination against RTI-causing pathogens in various populations including healthy non-elderly adults. Fewer randomized controlled trials have examined the effects of prebiotics or synbiotics on RTI-related outcomes in healthy non-elderly adults. Nevertheless, some studies conducted within that population and other populations have observed that certain prebiotics and synbiotics reduce the incidence, duration, and/or severity of RTI or improve immune responses to vaccinations against RTI-causing viruses. However, across all product classes, not all product formulations have shown benefit, and most have not been tested in multiple randomized controlled trials in military-relevant populations.

CONCLUSION

Dietary supplementation with certain gut microbiota-targeted interventions, and certain probiotics in particular, may provide viable strategies for reducing RTI-related illness in military personnel. Research in military populations is warranted to fully understand the magnitude of any military health and cost benefits, and to establish definitive recommendations for use.

Probiotics and Gut Health in Athletes

PURPOSE OF REVIEW

To provide a focused analysis of the challenges to gut health in athletes and examine recent research aimed at determining the impact of probiotics on preventing gastrointestinal (GI) symptoms and loss of barrier function in athletes.

RECENT FINDINGS

Frequency and severity of GI symptoms during training or competition were reduced by approximately one-third in studies demonstrating efficacy. Improvement of GI symptoms with probiotic supplementation was measured in both single-strain Lactobacillus and multi-strain Lactobacillus and Bifidobacterim probiotics, while improvement in gut barrier function was only measured for multi-strain probiotics. Likelihood of efficacy increased with duration of supplementation. The greatest efficacy for reducing GI symptom frequency and severity, as well as improving or preserving gut barrier function during exercise training and competition, appears to be for multi-strain Lactobacillus and Bifidobacterium probiotic cocktails supplemented for at least 11 weeks.

Plasma Amino Acid Response to Whey Protein Ingestion Following 28 Days of Probiotic (Bacillus subtilis DE111) Supplementation in Active Men and Women

We sought to determine if 28 days of probiotic supplementation influenced the plasma amino acid (AA) response to acute whey protein feeding.

METHODS

Twenty-two recreationally active men (n = 11; 24.3 ± 3.2 yrs; 89.3 ± 7.2 kg) and women (n = 11; 23.0 ± 2.8 yrs; 70.2 ± 15.2 kg) participated in this double-blind, placebo-controlled, randomized study. Before (PRE) and after 28 days of supplementation (POST), participants reported to the lab following a 10-hr fast and provided a resting blood draw (0 min), then subsequently consumed 25 g of whey protein. Blood samples were collected at 15-min intervals for 2 h post-consumption (15-120 min) and later analyzed for plasma leucine, branched-chain AA (BCAA), essential AA (EAA), and total AA (TAA). Participants received a probiotic (PROB) consisting of 1 x10-9 colony forming units (CFU) Bacillus subtilis DE111 (n = 11) or a maltodextrin placebo (PL) (n = 11) for 28 days. Plasma AA response and area under the curve (AUC) values were analyzed via repeated measures analysis of variance.

RESULTS

Our analysis indicated no significant (p < 0.05) differential responses for plasma leucine, BCAA, EAA, or TAA between PROB and PL from PRE to POST. AUC analysis revealed no group × time interaction for plasma leucine (p = 0.524), BCAA (p = 0.345), EAA (p = 0.512), and TAA (p = 0.712).

CONCLUSION

These data indicate that 28 days of Bacillus subtilis DE111 does not affect plasma AA appearance following acute whey protein ingestion.

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.

The Potential Impact of Probiotics on the Gut Microbiome of Athletes

There is accumulating evidence that physical fitness influences the gut microbiome and as a result, promotes health. Indeed, exercise-induced alterations in the gut microbiome can influence health parameters crucial to athletic performance, specifically, immune function, lower susceptibility to infection, inflammatory response and tissue repair. Consequently, maintenance of a healthy gut microbiome is essential for an athlete's health, training and performance. This review explores the effect of exercise on the microbiome while also investigating the effect of probiotics on various potential consequences associated with over-training in athletes, as well as their associated health benefits.

Precision Nutrition and the Microbiome Part II: Potential Opportunities and Pathways to Commercialisation

Modulation of the human gut microbiota through probiotics, prebiotics and dietary fibre are recognised strategies to improve health and prevent disease. Yet we are only beginning to understand the impact of these interventions on the gut microbiota and the physiological consequences for the human host, thus forging the way towards evidence-based scientific validation. However, in many studies a percentage of participants can be defined as 'non-responders' and scientists are beginning to unravel what differentiates these from 'responders;' and it is now clear that an individual's baseline microbiota can influence an individual's response. Thus, microbiome composition can potentially serve as a biomarker to predict responsiveness to interventions, diets and dietary components enabling greater opportunities for its use towards disease prevention and health promotion. In Part I of this two-part review, we reviewed the current state of the science in terms of the gut microbiota and the role of diet and dietary components in shaping it and subsequent consequences for human health. In Part II, we examine the efficacy of gut-microbiota modulating therapies at different life stages and their potential to aid in the management of undernutrition and overnutrition. Given the significance of an individual's gut microbiota, we investigate the feasibility of microbiome testing and we discuss guidelines for evaluating the scientific validity of evidence for providing personalised microbiome-based dietary advice. Overall, this review highlights the potential value of the microbiome to prevent disease and maintain or promote health and in doing so, paves the pathway towards commercialisation.

Exertional-heat stress-associated gastrointestinal perturbations during Olympic sports: Management strategies for athletes preparing and competing in the 2020 Tokyo Olympic Games

Exercise-induced gastrointestinal syndrome (EIGS) is a common characteristic of exercise. The causes appear to be multifactorial in origin, but stem primarily from splanchnic hypoperfusion and increased sympathetic drive. These primary causes can lead to secondary outcomes that include increased intestinal epithelial injury and gastrointestinal hyperpermeability, systemic endotoxemia, and responsive cytokinemia, and impaired gastrointestinal function (i.e. transit, digestion, and absorption). Impaired gastrointestinal integrity and functional responses may predispose individuals, engaged in strenuous exercise, to gastrointestinal symptoms (GIS), and health complications of clinical significance, both of which may have exercise performance implications. There is a growing body of evidence indicating heat exposure during exercise (i.e. exertional-heat stress) can substantially exacerbate these gastrointestinal perturbations, proportionally to the magnitude of exertional-heat stress, which is of major concern for athletes preparing for and competing in the upcoming 2020 Tokyo Olympic Games. To date, various hydration and nutritional strategies have been explored to prevent or ameliorate exertional-heat stress associated gastrointestinal perturbations. The aims of the current review are to comprehensively explore the impact of exertional-heat stress on markers of EIGS, examine the evidence for the prevention and (or) management of EIGS in relation to exertional-heat stress, and establish best-practice nutritional recommendations for counteracting EIGS and associated GIS in athletes preparing for and competing in Tokyo 2020.