The Impact of a 24-h Low and High Fermentable Oligo- Di- Mono-Saccharides and Polyol (FODMAP) Diet on Plasma Bacterial Profile in Response to Exertional-Heat Stress

Sports Dietitians Australia and Ultra Sports Science Foundation Joint Position Statement: A Practitioner Guide to the Prevention and Management of Exercise-Associated Gastrointestinal Perturbations and Symptoms

It is now well-established that exercise can disturb various aspects of gastrointestinal integrity and function. The pathophysiology of these perturbations, termed "exercise-induced gastrointestinal syndrome (EIGS)," can lead to exercise-associated gastrointestinal symptom (Ex-GIS) inconveniences. EIGS outcomes can impact physical performance and may lead to clinical manifestation warranting medical intervention, as well as systemic responses leading to fatality. Athlete support practitioners seek prevention and management strategies for EIGS and Ex-GIS. This current position statement aimed to critically appraise the role of EIGS and Ex-GIS prevention and management strategies to inform effective evidence-based practice and establish translational application. Intervention strategies with mostly consistent beneficial outcomes include macronutrient (i.e., carbohydrate and protein) intake and euhydration before and during exercise, dietary manipulation of fermentable oligo-, di-, and mono-saccharides and polyols (FODMAP), and gut training or feeding tolerance adjustments for the specific management of Ex-GIS from gastrointestinal functional issues. Strategies that may provide benefit and/or promising outcomes, but warrant further explorations include heat mitigating strategies and certain nutritional supplementation (i.e., prebiotics and phenols). Interventions that have reported negative outcomes included low-carbohydrate high-fat diets, probiotic supplementation, pharmaceutical administration, and feeding intolerances. Owing to individual variability in EIGS and Ex-GIS outcomes, athletes suffering from EIGS and/or support practitioners that guide athletes through managing EIGS, are encouraged to undertake gastrointestinal assessment during exercise to identify underlying causal and exacerbation factor/s, and adopt evidence-based strategies that provide individualized beneficial outcomes. In addition, abstaining from prevention and management strategies that present unclear and/or adverse outcomes is recommended.

Impact of moderate environmental heat stress during running exercise on circulating markers of gastrointestinal integrity in endurance athletes

In the present study, we aimed to determine the effect of moderate ambient heat stress on exercise-provoked patterns of "leaky gut" biomarkers and stress markers in well-trained athletes. Eleven triathletes performed a strenuous 1-h treadmill run, both under normal ambient conditions (N, 18-21°C) as well as under moderate heat environmental conditions (H, 28-30°C). Core body temperature (Tc), heart rate (HR), and rating of perceived exertion (RPE) significantly increased under both conditions, with significantly higher values during and after the H run. We observed a significant main effect of acute exercise on circulating leukocyte numbers, release of cell-free human DNA (cfDNA) but not bacterial DNA (bacDNA), and on plasma levels of intestinal fatty-acid binding protein (I-FABP), lipopolysaccharide-binding protein (LBP), endotoxin (LPS), and D-lactate. Exercising under H conditions accelerated the mobilization of circulating neutrophils and lymphocytes, and significantly affected the release of cfDNA, D-lactate, I-FABP, creatinine, and blood potassium levels. Multiple correlation analysis revealed a significant association between Tc, max and exercise-provoked release of cfDNA (r = 0.583, p = 0.012) as well as with I-FABP (r = 0.554, p = 0.026). Our data indicate that acute exercising and heat stress may not only affect paracellular but also transcellular intestinal permeability.

The Effects of Prebiotic Supplementation on Markers of Exercise-Induced Gastrointestinal Syndrome in Response to Exertional Heat Stress

Exercise perturbs various aspects of gastrointestinal integrity and function, which may lead to performance impeding gastrointestinal symptoms (GIS) and/or precipitate clinical issues warranting medical management. This study aimed to determine the impact of prebiotic supplementation on gastrointestinal integrity and functional status in response to exertional heat stress (EHS). Sixteen endurance athletes completed two trials of 3-hr running at 60% V˙O2max in 30 °C at baseline (T1) and following an 8-week supplementation period (T2), with 16 g/day prebiotic (PREBIOTIC) or matched placebo (PLACEBO). Blood samples were collected pre-EHS and post-EHS and in recovery for determination of stress response (cortisol), intestinal epithelial injury (intestinal fatty acid binding protein), bacterial endotoxemia (sCD14), and systemic inflammation (C-reactive protein). GIS and feeding tolerance variables were assessed throughout the EHS. Orocecal transit time was determined via a lactulose challenge given at 2.5 hr into EHS. Plasma cortisol (combined mean: +252 ng/ml), intestinal fatty acid binding protein (+800 pg/ml), and sCD14 (+487 ng/ml) concentrations increased in response to EHS in T1 (p ≤ .05), but not for C-reactive protein (+0.8 μg/ml; p > .05), in both PREBIOTIC and PLACEBO. PREBIOTIC supplementation resulted in a blunted intestinal fatty acid binding protein response on T2 (+316 pg/ml) compared with an increase (+1,001 ng/ml) in PLACEBO (p = .005). Lower sCD14 was observed at T2 (2,799 ng/ml) versus T1 (3,246 ng/ml) in PREBIOTIC only (p = .039). No intervention effects were observed for C-reactive protein. No difference within or between PREBIOTIC and PLACEBO at T1 and T2 was observed for orocecal transit time, GIS, and feeding tolerance. In conclusion, 8 weeks of prebiotic supplementation modestly attenuates EHS associated perturbations to intestinal integrity, but does not further impair gastrointestinal transit and/or exacerbate EHS associated GIS or feeding tolerance.

Towards Precision Sports Nutrition for Endurance Athletes: A Scoping Review of Application of Omics and Wearables Technologies

BACKGROUND

Endurance athletes require tailored nutrition strategies to optimize performance, recovery, and training adaptations. While traditional sports nutrition guidelines provide a foundational framework, individual variability in metabolic responses underscores the need for precision nutrition, informed by genetic, biological, and environmental factors. This scoping review evaluates the application of systems biology-driven sports nutrition for endurance athletes, focusing on 'omics' and wearable technologies.

METHODS

A scoping review of the literature was conducted in PubMed, Scopus, and Web of Science in accordance with the PRISMA-ScR checklist. Research questions, search strategies, and eligibility criteria were guided by the Population-Concept-Context framework with the following inclusion criteria: original research in English, involving endurance athletes, systems biology approaches, and nutritional interventions or continuous glucose monitoring (CGM).

RESULTS

Fifty-two studies were included, with distance runners as the most studied cohort. Eleven studies used metagenomics, eleven CGM, ten nutrigenetics, ten metabolomics, seven multi-omics, one proteomics, one epigenomics, and one lipidomics. Over half (n = 31; 60%) were randomized controlled trials (RCTs) with generally high methodological quality.

CONCLUSIONS

Most studies were proof-of-concept investigations aimed at assessing biomarkers; however, the evidence linking these biomarkers to performance, recovery, and long-term health outcomes in endurance athletes remains insufficient. Future research should focus on well-powered replicated crossover RCTs, multivariate N-of-1 clinical trials, 360-degree systems-wide approaches, and the validation of genetic impacts on nutritional interventions to refine dietary guidelines.

Exertional heat stress promotes the presence of bacterial DNA in plasma: A counterbalanced randomised controlled trial

OBJECTIVES

The primary aim was to explore the impact of exertional-heat stress (EHS) promoted exercise-associated bacteraemia. A secondary aim was to examine if an amino acid beverage (AAB) intervention may mitigate exercise-associated bacteraemia.

DESIGN

Counterbalanced randomised control trial.

METHODS

Twenty endurance trained male participants completed two randomised EHS trials. On one occasion, participants consumed a 237 mL AAB twice daily for 7 days prior, immediately before and every 20 min during EHS (2 h running at 60 % V̇O2max in 35 °C). On the other occasion, a water volume control (CON) equivalent was consumed. Whole blood samples were collected pre- and immediately post-EHS, and were analysed for plasma DNA concentration by fluorometer quantification after microbial extraction, and bacterial relative abundance by next generation 16s rRNA gene sequencing.

RESULTS

Increased concentration of microbial DNA in plasma pre- to post-EHS was observed on CON (pre-EHS 0.014 ng/μL, post-EHS 0.039 ng/μL) (p < 0.001) and AAB (pre-EHS 0.015 ng/μL, post-EHS 0.031 ng/μL) (p < 0.001). The magnitude of change from pre- to post-exercise on AAB was 40 % lower, but no significant difference was observed versus CON (p = 0.455). Predominant bacterial groups identified included: phyla-Proteobacteria (88.0 %), family-Burkholderiaceae (59.1 %), and genus-Curvibacter (58.6 %). No significant variation in absolute and relative change in α-diversity and relative abundance for phyla, family, and genus bacterial groups was observed in AAB versus CON.

CONCLUSIONS

The increased presence of microbial-bacterial DNA in systemic circulation in response to EHS appears positive in all participants. An amino acid beverage supplementation period prior to and consumption during EHS did not provide significant attenuation of EHS-associated bacteraemia.

Nourishing Physical Productivity and Performance On a Warming Planet - Challenges and Nutritional Strategies to Mitigate Exertional Heat Stress

PURPOSE OF REVIEW: Climate change is predicted to increase the frequency and severity of exposure to hot environments. This can impair health, physical performance, and productivity for active individuals in occupational and athletic settings. This review summarizes current knowledge and recent advancements in nutritional strategies to minimize the impact of exertional-heat stress (EHS). RECENT FINDINGS: Hydration strategies limiting body mass loss to < 3% during EHS are performance-beneficial in weight-supported activities, although evidence regarding smaller fluid deficits (< 2% body mass loss) and weight-dependent activities is less clear due to a lack of well-designed studies with adequate blinding. Sodium replacement requirements during EHS depends on both sweat losses and the extent of fluid replacement, with quantified sodium replacement only necessary once fluid replacement > 60-80% of losses. Ice ingestion lowers core temperature and may improve thermal comfort and performance outcomes when consumed before, but less so during activity. Prevention and management of gastrointestinal disturbances during EHS should focus on high carbohydrate but low FODMAP availability before and during exercise, frequent provision of carbohydrate and/or protein during exercise, adequate hydration, and body temperature regulation. Evidence for these approaches is lacking in occupational settings. Acute kidney injury is a potential concern resulting from inadequate fluid replacement during and post-EHS, and emerging evidence suggests that repeated exposures may increase the risk of developing chronic kidney disease. Nutritional strategies can help regulate hydration, body temperature, and gastrointestinal status during EHS. Doing so minimizes the impact of EHS on health and safety and optimizes productivity and performance outcomes on a warming planet.

Exertional Stress-induced Pathogenic Luminal Content Translocation - Friend or Foe?

The incidence of perturbed gastrointestinal integrity, as well as resulting systemic immune responses and gastrointestinal symptoms, otherwise known as exercised-induced gastrointestinal syndrome (EIGS), is common among individuals who partake in prolonged exercise. EIGS may cause the translocation of pathogenic material, including whole bacteria and bacterial endotoxins, from the lumen into circulation, which may progress into clinical consequences such as sepsis, and potentially subsequent fatality. However, further investigation is warranted to assess the possibility of food allergen and/or digestive enzyme luminal to circulatory translocation in response to exercise, and the clinical consequences. Findings from this narrative literature review demonstrate evidence that whole bacteria and bacterial endotoxins translocation from the gastrointestinal lumen to systemic circulation occurs in response to exercise stress, with a greater propensity of translocation occurring with accompanying heat exposure. It has also been demonstrated that food allergens can translocate from the lumen to systemic circulation in response to exercise stress and initiate anaphylaxis. To date, no research investigating the effect of exercise on the translocation of digestive enzymes from the lumen into systemic circulation exists. It is evident that EIGS and consequential pathogenic translocation presents life-threatening clinical implications, warranting the development and implementation of effective management strategies in at-risk populations.

The impact of 48 h high carbohydrate diets with high and low FODMAP content on gastrointestinal status and symptoms in response to endurance exercise, and subsequent endurance performance

This study investigated the effects of a high carbohydrate diet, with varied fermentable oligo-, di-, and mono-saccharide and polyol (FODMAP) content, before endurance exercise on gastrointestinal integrity, motility, and symptoms; and subsequent exercise performance. Twelve endurance athletes were provided with a 48 h high carbohydrate (mean ± SD: 12.1 ± 1.8 g kg day-1) diet on two separate occasions, composed of high (54.8 ± 10.5 g day-1) and low FODMAP (3.0 ± 0.2 g day-1) content. Thereafter, participants completed a 2 h steady-state running exercise at 60% of V ˙ O 2 max (22.9 ± 1.2 °C, 46.4 ± 7.9% RH), followed by a 1 h distance performance test. Pre-exercise and every 20 min during steady-state exercise, 100 mL maltodextrin (10% w/v) solution was consumed. A 150 mL lactulose (20 g) solution was consumed 30 min into the distance performance test to determine orocecal transit time (OCTT) during exercise. Blood was collected pre- and post exercise to determine gastrointestinal integrity biomarkers (i.e., I-FABP, sCD14, and CRP). Breath hydrogen (H2) and gastrointestinal symptoms (GIS) were determined pre-exercise, every 15 min, during and throughout recovery. No differences in gastrointestinal integrity biomarkers, OCTT, or distance completed were observed between trials. Pre-exercise total-GIS (1.3 ± 2.9 vs. 4.3 ± 4.4), gut discomfort (9.9 ± 8.1 vs. 15.8 ± 9.0), and upper-GIS (2.8 ± 2.6 vs. 5.7 ± 4.8) during exercise were less severe on high carbohydrate low FODMAP (HC-LFOD) versus high carbohydrate high FODMAP (HC-HFOD) (p < 0.05). Gut discomfort (3.4 ± 4.4 vs. 0.2 ± 0.6) and total-GIS (4.9 ± 6.8 vs. 0.2 ± 0.6) were higher during recovery on HC-LFOD versus HC-HFOD (p < 0.05). The FODMAP content of a 48 h high carbohydrate diet does not impact gastrointestinal integrity or motility in response to endurance exercise. However, a high FODMAP content exacerbates GIS before and during exercise, but this does not impact performance outcomes.