Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the mechanisms and use of probiotic supplementation to optimize the health, performance, and recovery of athletes. Based on the current available literature, the conclusions of the ISSN are as follows: Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO).Probiotic administration has been linked to a multitude of health benefits, with gut and immune health being the most researched applications.Despite the existence of shared, core mechanisms for probiotic function, health benefits of probiotics are strain- and dose-dependent.Athletes have varying gut microbiota compositions that appear to reflect the activity level of the host in comparison to sedentary people, with the differences linked primarily to the volume of exercise and amount of protein consumption. Whether differences in gut microbiota composition affect probiotic efficacy is unknown.The main function of the gut is to digest food and absorb nutrients. In athletic populations, certain probiotics strains can increase absorption of key nutrients such as amino acids from protein, and affect the pharmacology and physiological properties of multiple food components.Immune depression in athletes worsens with excessive training load, psychological stress, disturbed sleep, and environmental extremes, all of which can contribute to an increased risk of respiratory tract infections. In certain situations, including exposure to crowds, foreign travel and poor hygiene at home, and training or competition venues, athletes’ exposure to pathogens may be elevated leading to increased rates of infections. Approximately 70% of the immune system is located in the gut and probiotic supplementation has been shown to promote a healthy immune response. In an athletic population, specific probiotic strains can reduce the number of episodes, severity and duration of upper respiratory tract infections.Intense, prolonged exercise, especially in the heat, has been shown to increase gut permeability which potentially can result in systemic toxemia. Specific probiotic strains can improve the integrity of the gut-barrier function in athletes.Administration of selected anti-inflammatory probiotic strains have been linked to improved recovery from muscle-damaging exercise.The minimal effective dose and method of administration (potency per serving, single vs. split dose, delivery form) of a specific probiotic strain depends on validation studies for this particular strain. Products that contain probiotics must include the genus, species, and strain of each live microorganism on its label as well as the total estimated quantity of each probiotic strain at the end of the product’s shelf life, as measured by colony forming units (CFU) or live cells.Preclinical and early human research has shown potential probiotic benefits relevant to an athletic population that include improved body composition and lea...

The microorganisms in the gastrointestinal tract play a significant role in nutrient uptake, vitamin synthesis, energy harvest, inflammatory modulation, and host immune response, collectively contributing to human health. Important factors such as age, birth method, antibiotic use, and diet have been established as formative factors that shape the gut microbiota. Yet, less described is the role that exercise plays, particularly how associated factors and stressors, such as sport/exercise-specific diet, environment, and their interactions, may influence the gut microbiota. In particular, high-level athletes offer remarkable physiology and metabolism (including muscular strength/power, aerobic capacity, energy expenditure, and heat production) compared to sedentary individuals, and provide unique insight in gut microbiota research. In addition, the gut microbiota with its ability to harvest energy, modulate the immune system, and influence gastrointestinal health, likely plays an important role in athlete health, wellbeing, and sports performance. Therefore, understanding the mechanisms in which the gut microbiota could play in the role of influencing athletic performance is of considerable interest to athletes who work to improve their results in competition as well as reduce recovery time during training. Ultimately this research is expected to extend beyond athletics as understanding optimal fitness has applications for overall health and wellness in larger communities. Therefore, the purpose of this narrative review is to summarize current knowledge of the athletic gut microbiota and the factors that shape it. Exercise, associated dietary factors, and the athletic classification promote a more "health-associated" gut microbiota. Such features include a higher abundance of health-promoting bacterial species, increased microbial diversity, functional metabolic capacity, and microbial-associated metabolites, stimulation of bacterial abundance that can modulate mucosal immunity, and improved gastrointestinal barrier function.

Purpose To evaluate the effects of probiotic supplementation on gastrointestinal (GI) symptoms, circulatory markers of GI permeability, damage, and markers of immune response during a marathon race. Methods Twenty-four recreational runners were randomly assigned to either supplement with a probiotic (PRO) capsule [25 billion CFU Lactobacillus acidophilus (CUL60 and CUL21), Bifidobacterium bifidum (CUL20), and Bifidobacterium animalis subs p. Lactis (CUL34)] or placebo (PLC) for 28 days prior to a marathon race. GI symptoms were recorded during the supplement period and during the race. Serum lactulose:rhamnose ratio, and plasma intestinal-fatty acid binding protein, sCD14, and cytokines were measured pre- and post-races. Results Prevalence of moderate GI symptoms reported were lower during the third and fourth weeks of the supplement period compared to the first and second weeks in PRO ( p < 0.05) but not PLC ( p > 0.05). During the marathon, GI symptom severity during the final third was significantly lower in PRO compared to PLC ( p = 0.010). The lower symptom severity was associated with a significant difference in reduction of average speed from the first to the last third of the race between PLC (− 14.2 ± 5.8%) and PRO (− 7.9 ± 7.5%) ( p = 0.04), although there was no difference in finish times between groups ( p > 0.05). Circulatory measures increased to a similar extent between PRO and PLC ( p > 0.05). Conclusion Probiotics supplementation was associated with a lower incidence and severity of GI symptoms in marathon runners, although the exact mechanisms are yet to be elucidated. Reducing GI symptoms during marathon running may help maintain running pace during the latter stages of racing.

PurposeTo examine the dose–response effects of acute glutamine supplementation on markers of gastrointestinal (GI) permeability, damage and, secondary, subjective symptoms of GI discomfort in response to running in the heat.MethodsTen recreationally active males completed a total of four exercise trials; a placebo trial and three glutamine trials at 0.25, 0.5 and 0.9 g kg−1 of fat-free mass (FFM) consumed 2 h before exercise. Each exercise trial consisted of a 60-min treadmill run at 70% of in an environmental chamber set at 30 °C. GI permeability was measured using ratio of lactulose to rhamnose (L:R) in serum. Plasma glutamine and intestinal fatty acid binding protein (I-FABP) concentrations were determined pre and post exercise. Subjective GI symptoms were assessed 45 min and 24 h post-exercise.ResultsRelative to placebo, L:R was likely lower following 0.25 g kg−1 (mean difference: − 0.023; ± 0.021) and 0.5 g kg−1 (− 0.019; ± 0.019) and very likely following 0.9 g kg− 1 (− 0.034; ± 0.024). GI symptoms were typically low and there was no effect of supplementation.DiscussionAcute oral glutamine consumption attenuates GI permeability relative to placebo even at lower doses of 0.25 g kg−1, although larger doses may be more effective. It remains unclear if this will lead to reductions in GI symptoms. Athletes competing in the heat may, therefore, benefit from acute glutamine supplementation prior to exercise in order to maintain gastrointestinal integrity.

Purpose To investigate the effects of high-intensity interval (HIIT) running on markers of gastrointestinal (GI) damage and permeability alongside subjective symptoms of GI discomfort. Methods Eleven male runners completed an acute bout of HIIT (eighteen 400 m runs at 120% O2max ) where markers of GI permeability, intestinal damage and GI discomfort symptoms were assessed and compared with resting significantly increased (p < 0.001) during and in the recovery period from HIIT whereas no changes were observed during rest. Mild-symptoms of GI discomfort, were reported immediately-and 24 h post-HIIT, although these symptoms did not correlate to GI permeability or I-FABP. Conclusion Acute HIIT increased GI permeability and intestinal I-FABP release, although these do not correlate with symptoms of GI discomfort. Furthermore, by using serum sampling, we provide data showing that it is possible to detect changes in intestinal permeability that is not observed using urinary sampling over a shorter timeperiod.

Key points Reduced carbohydrate (CHO) availability before and after exercise may augment endurance training‐induced adaptations of human skeletal muscle, as mediated via modulation of cell signalling pathways. However, it is not known whether such responses are mediated by CHO restriction, energy restriction or a combination of both. In recovery from a twice per day training protocol where muscle glycogen concentration is maintained within 200–350 mmol kg−1 dry weight (dw), we demonstrate that acute post‐exercise CHO and energy restriction (i.e. < 24 h) does not potentiate potent cell signalling pathways that regulate hallmark adaptations associated with endurance training. In contrast, consuming CHO before, during and after an acute training session attenuated markers of bone resorption, effects that are independent of energy availability. Whilst the enhanced muscle adaptations associated with CHO restriction may be regulated by absolute muscle glycogen concentration, the acute within‐day fluctuations in CHO availability inherent to twice per day training may have chronic implications for bone turnover. Abstract We examined the effects of post‐exercise carbohydrate (CHO) and energy availability (EA) on potent skeletal muscle cell signalling pathways (regulating mitochondrial biogenesis and lipid metabolism) and indicators of bone metabolism. In a repeated measures design, nine males completed a morning (AM) and afternoon (PM) high‐intensity interval (HIT) (8 × 5 min at 85% V̇O2 peak ) running protocol (interspersed by 3.5 h) under dietary conditions of (1) high CHO availability (HCHO: CHO ∼12 g kg−1, EA∼ 60 kcal kg−1 fat free mass (FFM)), (2) reduced CHO but high fat availability (LCHF: CHO ∼3 (−1, EA∼ 60 kcal kg−1 FFM) or (3), reduced CHO and reduced energy availability (LCAL: CHO ∼3 g kg−1, EA∼ 20 kcal kg−1 FFM). Muscle glycogen was reduced to ∼200 mmol kg−1 dw in all trials immediately post PM HIT (P < 0.01) and remained lower at 17 h (171, 194 and 316 mmol kg−1 dw) post PM HIT in LCHF and LCAL (P < 0.001) compared to HCHO. Exercise induced comparable p38MAPK phosphorylation (P < 0.05) immediately post PM HIT and similar mRNA expression (all P < 0.05) of PGC‐1α, p53 and CPT1 mRNA in HCHO, LCHF and LCAL. Post‐exercise circulating βCTX was lower in HCHO (P < 0.05) compared to LCHF and LCAL whereas exercise‐induced increases in IL‐6 were larger in LCAL (P < 0.05) compared to LCHF and HCHO. In conditions where glycogen concentration is maintained within 200–350 mmol kg−1 dw, we conclude post‐exercise CHO and energy restriction (i.e. < 24 h) does not potentiate cell signalling pathways that regulate hallmark adaptations associated with endurance training. In contrast, consuming CHO before, during and after HIT running attenuates bone resorption, effects that are independent of energy availability and circulating IL‐6.

Background In vitro and animal studies suggest probiotic supplementation can enhance intestinal absorption and whole body oxidation rates of glucose. Objective This study investigated the effects of multi‐strain probiotics supplementation on substrate utilization, markers of gastrointestinal permeability and damage and subjective symptoms of discomfort and performance during endurance cycling. Methods and Design Nine male cyclists (age 23 ± 4 yrs, V̇O2max 62.1 ± 4.7 mL·kg−1·min−1) were randomized to two periods of daily supplementation with a probiotics capsule (25 billion CFU of Lactobacillus acidophilus (CUL60 and CUL21), Bifidobacterium bifidum (CUL20), Bifidobacterium animalis subsp. lactis (CUL34), Proven Probiotics) or placebo for four weeks, separated by a 14‐day washout period (double‐blind cross‐over trial). After each supplementation period, cyclists consumed a 10% maltodextrin solution (initial 8 mL·kg−1 bolus at commencement of exercise and 2 mL·kg−1 every subsequent 15 min) while exercising for 120 minutes at 55% Wmax. This was followed immediately by a 100 kJ time trial performance test. Markers of GI permeability, damage and GI discomfort were assessed. Oxidation rates of the ingested maltodextrin drinks were calculated from the 13C‐enrichment of plasma glucose and breath 13CO2 production during the 120 minutes exercise period. Results Probiotic supplementation resulted in an increase of total carbohydrate (CHO) oxidation (2.12 ± 0.30 vs 1.81 ± 0.44 g·min1, P = 0.019) and the peak oxidation of an ingested maltodextrin drink (0.84 ± 0.10 vs 0.77 ± 0.09 g·min−1 of glucose equivalents, P = 0.016) during exercise. Total fat oxidation was reduced following probiotic supplementation compared to placebo (P = 0.004). There were also significant differences in plasma insulin, NEFA and glycerol between trials. Differences between markers of GI damage and permeability were not significant, as was time trial performance (P > 0.05). Conclusions Probiotic supplementation enhances total and ingested CHO oxidation while simultaneously attenuating total fat oxidation during moderate intensity cycling. Probiotic supplementation did not change GI symptoms, time trial performance and markers of intestinal damage and permeability. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Check the metadata sheet to make sure that the header information, especially author names and the corresponding affiliations are correctly shown.• Check the questions that may have arisen during copy editing and insert your answers/ corrections.• Check that the text is complete and that all figures, tables and their legends are included. Also check the accuracy of special characters, equations, and electronic supplementary material if applicable. If necessary refer to the Edited manuscript.• The publication of inaccurate data such as dosages and units can have serious consequences.Please take particular care that all such details are correct.• Please do not make changes that involve only matters of style. We have generally introduced forms that follow the journal's style. Substantial changes in content, e.g., new results, corrected values, title and authorship are not allowed without the approval of the responsible editor. In such a case, please contact the Editorial Office and return his/her consent together with the proof.• If we do not receive your corrections within 48 hours, we will send you a reminder.• Your article will be published Online First approximately one week after receipt of your corrected proofs. This is the official first publication citable with the DOI. Further changes are, therefore, not possible.• The printed version will follow in a forthcoming issue.