Engaging in moderate physical exercise provides, in the long term, benefits for the immune system. That is, maintaining an active life will improve our immune system, making us less likely to develop infections, etc. However, intense exercise and the continuous stress involved in demanding physical preparation can weaken the immune system, facilitating infectious processes.
As shown by an article that included almost 8000 samples from more than 2000 athletes (Horn et al. 2010), endurance athletes such as cyclists and triathletes have a lower number of white blood cells (cells responsible for defense against inflammatory processes) than other athletes. In fact, 16% of these athletes showed values below the reference levels. Additionally, intense exercise seems to acutely decrease immune function, making them even more prone to infections. These results could partly explain the high prevalence of infections in endurance athletes, who have a greater predisposition to suffer from diseases related to infectious processes (especially respiratory ones such as bronchitis) than the general population (Harris 2011).
That is why it is important to improve immune function in these athletes, especially during periods of high training load. In this regard, following a diet that provides an adequate amount of calories and nutrients (carbohydrates, vitamins, proteins, etc.) will be essential. Additionally, although the evidence is not unanimous on this matter, it has been suggested that supplementation with glutamine could be effective in improving immune function in athletes.
A study (Castell 1996) in 200 endurance athletes observed that the prevalence of infections after their competitions was approximately 25-50%, being higher after ultra-endurance sports than in those of shorter distance (e.g., 10 km race). However, the results showed that those who took 5 grams of glutamine after exercise had a lower prevalence of infections than those who took a placebo (20 vs 50%, approximately). Similarly, a study (Song 2015) conducted over 6 weeks of high training load evaluated the effects of taking glutamine (10 g per day) or placebo on immune function. These authors observed that the CD4+/CD8+ ratio (an indicator of immune function, and therefore of susceptibility to infections) at the end of the training period was significantly higher in athletes supplemented with glutamine.
In summary, athletes have a higher risk of infection than the general population, especially during periods of high training load. For this reason, it is important to develop strategies to improve their immune function, among which following an adequate diet plays a fundamental role. The intake of glutamine seems to be effective in hyper-catabolic processes such as in disease states, and it could also be effective (especially from 200 mg/kg) in athletes subjected to high stress.
References
- Castell LM (1996) Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol Occup Physiol 73:488–490. doi: 10.1007/BF00334429
- Harris MD (2011) Infectious disease in athletes. Curr Sports Med Rep 10:84–89. doi: 10.1249/JSR.0b013e3182142381
- Horn PL, Pyne DB, Hopkins WG, Barnes CJ (2010) Lower white blood cell counts in elite athletes training for highly aerobic sports. Eur J Appl Physiol 110:925–932. doi: 10.1007/s00421-010-1573-9
- Song Q (2015) Glutamine supplementation and immune function during heavy load training.
AUTHOR
Pedro Valenzuela
Researcher in the Physiology Unit at the University of Alcalá and the Performance Monitoring Unit at the Sports Medicine Center (AEPSAD, Madrid High Performance Center).
Website: www.fissac.com
