Running: an ally of the immune system?

Occasional running is often associated in the common imaginary with beneficial effects on the body, however, is there enough evidence to support physical activity as an ally in the development of an effective immune system?

Running has numerous beneficial effects on the immune system, as demonstrated by the overproduction of several antibacterial molecules without differences between men and women, with a resulting better control of inflammation for example in the salivary level (Gillum TL, et al. J Strenght Cond Res 2015, Gillum TL, et al. Exerc Immunol Rev 2014).

However, the intensity of physical activity is a determining factor for the effects on the immune system; in fact extreme race, such as ultra marathon (50-100 km), causes an important physical stress that can reduce the production of antibacterial molecules salivary, which however, would  seem to be associated with an increased risk of respiratory infections (Gillum TL, et al. J Strenght Cond Res 2013; Gill SK, et al. Int J Sport Med 2014).

Nevertheless, the ultramarathon results also as alterations in the values of white blood cells, which can be doubled for hyper production/release of immature forms but do not protect against infections. The increase in inflammation is also associated with an elevation of the serum enzymes indicative of muscle damage, particularly creatine kinase -CK (Zakovska A, et al. Front Physiol 2017;  Nieman DC, et al. Brain Behav Immun 2014).

Individual predisposing factors are partly responsible for the altered response to infections that are observed in elite runners, as subjects suffering from upper respiratory infections have on average lower values of salivary / IgA antibodies/immunoglobulins than those who are not get affected  (Ihalainen JK, et al. Appl Physiol Nutr Metab 2016). The climatic factors could influence the immune response and outdoor activity during winter time is often reduced. However, a recent study has shown that anaerobic physical activity in the cold has no effect on the immune system compared with neutral climatic conditions, however,  activity in the cold elicits  minor  fluctuations in salivary lymphocyte levels (Carlson LA, et al. J Strenght Cond Res 2017).

The supplementation with carbohydrates or other supplements is often recommended to enhance physical activity, but it is not clear whether some nutrients can modify the immune response. Carbohydrates reduce the immune response, while a study of individuals who carry out physical activity has shown no differences in the immune response following prolonged exercise. On the other hand, blood zinc levels increase significantly with aerobic exercise, with possible antioxidant effects on metabolism, and on the immune system (Chu A, et al. Med Sci Sports Exerc 2016). Supplements based on fish oil may increase the proliferation of white blood cells and reduce proinflammatory molecules in marathon runners. (Santos C, et al. Int J Sport Nutr Exerc Meab 2013).

In conclusion, occasional running at moderate intensity is expected to have positive effects on the immune system, stimulating the production of some antibacterial molecules, with no apparent differences in activity in the cold. However, intense physical activity with high impact may ultimately reduce the immune system function and increase the risk of respiratory infections. While definitive evidence is awaited, some supplements could help decrease the impact of a harsh physical activity on the immune system.

(C) 2018 Carlo Selmi, MD PhD

Assistant Professor of Rheumatology, University of Milan
Head, Rheumatology and Clinical Immunology, Humanitas Clinical and Research Center
Assistant Professor of Medicine, University of California, Davis