Optimising athletic health and performance through the gut-muscle axis

Sports Nutritionists and coaches are always seeking ways of improving the wellbeing and performance of their athletes. One such target is the gut microbiota, and research is emerging to show a critical relationship between commensal gut microbes and skeletal muscle, referred to as the gut-muscle axis. This axis describes how gut microbes and their derived metabolites can influence muscle mass, muscle quality and muscle function, which could be of relevance in the context of sport and performance, as well as from a clinical perspective in ageing and muscle-wasting disorders (Chew et al., 2023).

Role of short chain fatty acids (SCFAs) and the immune system

Research has shown that frequent, moderate-intensity exercise is beneficial to health and can support a favourable microbiota balance, leading to higher levels of beneficial bacteria and metabolites, such as short chain fatty acids (SCFAs). SCFAs, such as acetate, lactate and butyrate, are produced as a by-product of the anaerobic fermentation of indigestible dietary carbohydrates by beneficial bacteria (van der Hee and Wells., 2021). SCFAs can increase energy harvest from food and act as an energy substrate for skeletal muscle, and for the athlete, this enhanced production could have ergogenic benefits (Bongiovanni et al., 2021; van der Hee and Wells., 2021).

During the height of a competitive season athlete wellbeing and recovery can be compromised due to high intensity and long frequency training. Between 20 and 60% athletes experience overtraining during their careers, and this can best be described as an imbalance between training and recovery that leads to declines in health and performance (Weakley et al., 2022). Overtraining can cause excessive inflammation, reduced immune function and higher circulating levels of reactive oxygen species (ROS) as a result of increased skeletal muscle effort (Giron et al., 2022;Przewłócka et al., 2020). The presence of high levels of ROS can reduce protein synthesis and muscle regeneration, and importantly, this disruption in muscle metabolism could result in muscle atrophy and impaired muscle function (He et al., 2017;Przewłócka et al., 2020).

Provision of nutrients

The gut microbiota are capable of synthesising vitamins de novo, such as B vitamins (riboflavin, cobalamin) and vitamin K (LeBlanc et al., 2013). Whilst little is known about these vitamins in the context of muscle health, early pre-clinical and clinical research suggests that they could play a role in regulating muscle mass, myogenesis and aiding muscle recovery (Alonso et al., 2022). Certain B vitamins, such as pyridoxine (B6), are also involved in glucose metabolism, supporting the transformation of hepatic and muscular glycogen into glucose, therefore suggestive of a role in energy provision to the muscles (Brancaccio et al., 2022).

As B-vitamins are water-soluble, they are not stored by the body and require daily replenishment. This is a particularly important consideration as exercise stresses metabolic pathways that require B-group vitamins, thus potentially increasing nutrient needs (Gonçalves and Portari., 2021). There is also a risk of B vitamins being lost in small quantities during exercise as a result of excessive perspiration and urination, particularly in climates of high heat and humidity where significant water-loss may occur, and where nutrient demands from food are not met (Clarkson., 2011). Deficiencies of B vitamins are associated with the onset of muscle-related symptoms, such as muscle fatigue, spasms and weakness, and reduced reflexes, and are therefore of particular importance in the context of muscle health in sporting populations (Brancaccio et al., 2022; Calderón-Ospina et al., 2019). Whilst deficiencies of these vitamins are unlikely, athletes may have insufficient quantities that could impact on health and performance.

The Takeaway

The gut-muscle axis is emerging as an important player in health and could be of relevance in both athletic and clinical populations. Whilst research is in its infancy, the gut microbiota could play a role in aiding muscular repair, maintaining muscle mass and supporting sports performance through the production of key metabolites and via crosstalk with the immune system. Furthermore, commensal gut microbes may also be important for the provision of key nutrients required for optimal muscular function.


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