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Immune System: The Role of Exercise

The immune system is the hot topic of discussion during the trying times of the COVID-19 pandemic. There has been a constant barrage of misinformation from claiming certain diets to certain foods as cures to COVID-19 . Some claims are harmless such as garlic, consuming citrus fruits , ginger and turmeric, which won’t boost your immune system but won’t do much damage. However, there are potentially harmful claims like overdosing Vitamins, consuming colloidal silver and self medicating with chloroquine. Despite the overwhelming information on the internet, there is no food which can magically “boost your immune system” . Good immunity takes months and years to build with simple yet hard to implement practice of healthy eating, exercise , adequate sleep and leading a stress free life . In a three part series I will cover how the immune system is impacted by exercise, diet and sleep & stress. In order to develop a better understanding of the basics of the immune system, it is worth reading on the importance of protein for the immune system.

You can check out some of the myths associated with COVID-19 and the widespread misinformation in the following video

Exercise: How much is too much?

Exercise immunology is a fairly new branch of sports science. The impact of exercise on the health of an athlete has gained fair amount of attention in recent times. Based on the current evidence, there seems to be compelling evidence to suggest exercise is beneficial for the immune system . However, heavy exertion is counterproductive. While analyzing the role of exercise and the immune system one needs to take into account other factors as well. The following diagram demonstrates the various factors which can affect the immune system of an athlete.

Fig 1: Psychological and physical factors which affects the immune system [1]

It is a widely held belief since the early days of exercise immunology research that upper respiratory tract infections (URTI) in athletes are directly impacted due to heavy workload during training. Recent evidence based on randomized control trials indicates role of sleep, stress, nutrition , pathogen exposure and travel also affect the incidence of URTIs in athletes. Fig 2 demonstrates that relationship between exercise and URTIs tend to follow a J curve where moderate exercise actually lowers the risk of URTIs.

Fig 2: Relationship between exercise intensity and probability of Upper Respiratory Tract Infection [2]

One can conclude that between not working out and working out regularly,the later is better. Exercise has also been proven to reduce inflammation. As mentioned in the article on protein and immune system cytokines play a vital role in keeping our immune system in check. In simple words cytokines prevent our immune system from going overboard and attacking our body’s own cells. During a 60 minute bout of moderate intensity exercise it was observed that anti pathogen activity in tissues were enhanced. Parallely anti inflammatory cytokines , T- cells and immature B-cells all of which play an important role in the immune system were circulated[3][4]. There was a clear reduction in inflammation which is particularly beneficial for overweight and obese individuals.

Don’t skip your workout

In conclusion it is clear that exercise is beneficial for the immune system. It helps reduce inflammation , recirculate pathogen fighting antibodies and helps the immune system act on carcinogenic cells. Fig 3 summarizes the positive effects of exercise on the immune system

Fig 3: Impact on Exercise on Immune system and inflammation [5]

However, in the current COVID-19 pandemic it is advisable not to over exert yourself. The evidence suggests a heavy workload is not advisable. Incidence of Upper Respiratory Tract Infections (URTIs) increase with increasing workload. Hence it is best to workout regularly but lightly to ensure the immune system is not stressed.

References

  1. Neil P. Walsh Recommendations to maintain immune health in athletes European Journal of Sport Science Volume 18, 2018 – Issue 6 pp 820-831
  2. D.C. Nieman Is infection risk linked to exercise workload? Med Sci Sports Exerc, 32 (Suppl. 7) (2000), pp. S406-S411
  3. G.R. Adams, F.P. Zaldivar, D.M. Nance, E. Kodesh, S. Radom-Aizik, D.M. Cooper Exercise and leukocyte interchange among central circulation, lung, spleen, and muscle Brain Behav Immun, 25 (2011), pp. 658-666
  4. A.B. Bigley, K. Rezvani, C. Chew, T. Sekine, M. Pistillo, B. Crucian, et al.Acute exercise preferentially redeploys NK-cells with a highly-differentiated phenotype and augments cytotoxicity against lymphoma and multiple myeloma target cells Brain Behav Immun, 39 (2014), pp. 160-171
  5. David Neimen Lauren Wentz The compelling link between physical activity and the body’s defense system Journal of Sport and Health Science Volume 8, Issue 3, May 2019, Pages 201-217

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