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The balancing act – Athletes and the gut microbiome  

What is the ‘gut’? 

The human gut microbiome comprises of a richly diverse ecosystem housing over 100 trillion microorganisms, including bacteria, viruses, fungi, and archaea.1 Its profound influence on overall health is multifaceted, encompassing crucial roles in digestion, regulating the immune system, reducing risk of chronic diseases such as cardiovascular disease and type 2 diabetes; and mental health disorders, among others.2 As such, the intricate interplay between the gut (also referred to as ‘intestinal’) microbiota and human health underscores the significance of lifestyle factors, including dietary patterns, hydration status, physical activity, stress management, and sleep quality, in shaping intestinal health.2 

Where does exercise fit in with intestinal health? 

It is widely acknowledged that exercise confers a myriad of health advantages, across physical health and mental well-bring. Benefits includes the management of blood pressure, reduction of blood cholesterol levels, mitigation of cardiovascular risks including heart attacks, reducing risk of osteoporosis through strong bones and muscles, immunity and an improved mental health (reducing stress, feeling relaxed and better mood).3,4 Moreover, research has shown exercise and intestinal health are interconnected.5,6 

Exercise enhances and supports the diversity of the gut microbiota by stimulating the growth of beneficial bacteria, promotes the production of short-chain fatty acids (such as, butyrate, propionate, and acetate) which has anti-inflammatory benefits, increased gut motility and reduced transit time, modulate gut hormones and protection against gastrointestinal disorders and colon cancer.7,8 Research has shown in athletes a highly diverse gut microbiota with an enrichment of beneficial bacteria including Bifidobacterium, Lactobacillus, Faecalibacterium and Akkermansia muciniphila.8,9 There are many benefits these beneficial bacteria provide, a commonality across the four is providing anti-inflammatory properties and regulation of the immune system.10-13 It is imperative to note that such microbial alterations may be contingent upon the intensity and modality of exercise undertaken. 8,9 

When exercise is too much for the gut 

In the literature, a j-curve shape (Figure 1) is utilised to display the implications of excessive exercise as well as sedentary individuals, with both ends of the spectrum showing a compromised gut microbiota and immunity with too little and/or excessive exercise. Hence, there seems to be an optimal threshold with moderate-high intensity on intestinal health an ideal middle ground.3,9 

Figure 1. Extracted figure illustrating the hypothesis effect of varying degrees of exercise on gut health, immunity and URTI’s.9 

Moderate to high-intensity exercise has shown to positively change the gut microbiota diversity, reduced inflammation, and intestinal permeability.5,6,9 However, when physical activity is too intense, the imbalance between time/intensity of training, recovery and the psycho-physical stress athletes experience can exemplify negative implications, with the aforementioned positive benefits may have the opposite results.7 This is evident in individuals participating in exhausting physical exercise i.e. elite athletes, who experience an increased risk of upper respiratory tract infections (URTI), supressed immunity and inflammation.7,9 Additionally, consequently, the integrity of the gut barrier may be compromised enhancing intestinal permeability, this allows entrance of pathogenic bacteria and exacerbates dysbiosis.3,9 In dysbiosis, there is an imbalance of bacteria in the gut, with an overgrowth of harmful or pathogenic bacteria, whilst a decrease in beneficial bacteria, negatively impacting the diversity and composition of the intestinal microbiota.7,9  

How can athletes support their intestinal microbiota?  

Due to the high physical requirements elite athletes endure it can put their gut under duress. Implementing healthy lifestyle choices is important to support their physical and mental health, and their overall well-being to ultimately perform at their best. Below is a list of strategies athletes can utilise to support their intestinal microbiota: 

  1. Prioritise whole, nutrient-dense foods: Aim to include fruits, vegetables, whole grains, lean proteins and healthy fats, to provide essential nutrients and fibre to support a diverse intestinal microbiota. 
  1. Incorporate fermented foods: Fermented foods like yoghurt, kefir, sauerkraut, kimchi, and kombucha contain beneficial probiotic bacteria that can help replenish and maintain a healthy intestinal microbiota. 
  1. Strain-specific probiotic supplement (if necessary): A supplement supported by evidence-based research in adequate quantities (at least 1 billion colony forming units) has the ability to provide individualised support e.g. immunity, gut inflammation and beneficial bacteria diversity, to name a few benefits.  
  1. Prebiotics: Prebiotics are non-digestible fibres that nourish beneficial gut bacteria. Foods rich in prebiotics include garlic, onions, leeks, asparagus, bananas, and whole grains. Including these foods in the diet feed the beneficial bacteria in the gut and can support the growth of healthy gut bacteria.  
  1. Stay hydrated: Adequate hydration is essential for supporting optimal digestion and nutrient absorption. Athletes should aim to drink plenty of water actively throughout the day, especially before, during, and after training sessions. 
  1. Minimise stress: Chronic stress can negatively impact gut health and disrupt the balance of the intestinal microbiota. Incorporating stress-reducing practices such as mindfulness, meditation, and adequate sleep can help support a healthy gut-brain axis. If you or someone else is struggling with mental wellness, we recommend seeking support.  
  1. Adequate rest and recovery: Enough time to recover in-between training sessions/match/game day etc can assist in muscle repair and growth, injury prevention and reduce risk of overtraining.  

Conclusion

The gut is a powerful tool impacting many facets of the body. Lifestyle factors such as exercise has shown positive benefits for the gut including improved growth and diversity, immunity and increased protection of gastrointestinal diseases. However, there is a balance required between exercise intensity/duration and intestinal health. Strenuous and exhausting exercise leaves the aforementioned symptoms diminished. Optimising a healthy lifestyle through, nutrient dense foods and fluids, fermented foods, stress relieving strategies and adequate rest will assist in supporting overall intestinal health and wellness.  

References:  

  1. Kassinen A, Krogius-Kurikka L, Mäkivuokko H, et al. The Fecal Microbiota of Irritable Bowel Syndrome Patients Differs Significantly From That of Healthy Subjects. Gastroenterology. 2007;133(1):24-33. doi:https://doi.org/10.1053/j.gastro.2007.04.005  
  1. Services D of H & H. Gut health. www.betterhealth.vic.gov.au. Published March 23, 2023. https://www.betterhealth.vic.gov.au/health/healthyliving/gut-health  
  1. Simpson RJ, Kunz H, Agha N, Graff R. Exercise and the Regulation of Immune Functions. Progress in Molecular Biology and Translational Science. 2015;135:355-380. doi:https://doi.org/10.1016 
    /bs.pmbts.2015.08.001  
  1. Better Health Channel. Physical activity – it’s important. Vic.gov.au. Published 2018. https://www.betterhealth.vic.gov.au/health/healthyliving/physical-activity-its-important 
  1. Clauss M, Gérard P, Mosca A, Leclerc M. Interplay Between Exercise and Gut Microbiome in the Context of Human Health and Performance. Frontiers in Nutrition. 2021;8. doi:https: 
    //doi.org/10.3389/fnut.2021.637010 
  1. Boytar AN, Skinner TL, Wallen RE, Jenkins DG, Dekker Nitert M. The Effect of Exercise Prescription on the Human Gut Microbiota and Comparison between Clinical and Apparently Healthy Populations: A Systematic Review. Nutrients. 2023;15(6):1534. doi:https://doi.org/10.3390/nu15061534 
  1. Wegierska AE, Charitos IA, Topi S, Potenza MA, Montagnani M, Santacroce L. The Connection Between Physical Exercise and Gut Microbiota: Implications for Competitive Sports Athletes. Sports Medicine. Published online May 21, 2022. doi:https://doi.org/10.1 
    007/s40279-022-01696-x 
  1. Mohr AE, Jäger R, Carpenter KC, et al. The athletic gut microbiota. Journal of the International Society of Sports Nutrition. 2020;17(1). doi:https://doi.org/10.1186/s129 
    70-020-00353- 
  1. O’Brien MT, O’Sullivan O, Claesson MJ, Cotter PD. The Athlete Gut Microbiome and its Relevance to Health and Performance: A Review. Sports Medicine. Published online November 18, 2022. doi:https://doi.org/10.1007/s40279-022-01785-x 
  1. Chen J, Chen X, Ho CL. Recent Development of Probiotic Bifidobacteria for Treating Human Diseases. Frontiers in Bioengineering and Biotechnology. 2021;9. doi:https://doi.org/10.3389/fbioe.2021.770248 
  1. Rastogi S, Singh A. Gut microbiome and human health: Exploring how the probiotic genus Lactobacillus modulate immune responses. Frontiers in Pharmacology. 2022;13. doi:https://doi.org/10.3389/fphar.2022.1042189 
  1. Martín R, Rios-Covian D, Eugénie Huillet, et al. Faecalibacterium: a bacterial genus with promising human health applications. Fems Microbiology Reviews. 2023;47(4). doi:https://doi.org/10.1093/femsre/fuad039 
  1. Chiantera V, Laganà AS, Basciani S, Nordio M, Bizzarri M. A Critical Perspective on the Supplementation of Akkermansia muciniphila: Benefits and Harms. Life. 2023;13(6):1247. doi:https://doi.org/10.3390/life13061247