Can exercise ‘boost’ your immune system?

It’s that time of year again - cold and flu season is peaking, RSV is on the rise, and COVID-19 is not yet a thing of the past. Marketing around ‘immune-boosting’ remedies is also ramping up making it increasingly difficult to know how best to protect you and your family from community-acquired infectious disease. Aside from vaccination, there is limited high-quality evidence supporting therapies that can prevent illness by bolstering the immune response, but the emerging evidence around exercise for immune system support is promising! Exercise is also relatively inexpensive, safe, and provides a host of other health benefits, but more on that later.

So, the answer to the question is yes, recent meta-analysis data suggests that exercise is associated with lower rates of infection and infectious disease-related mortality by 31% and 37% (1). Regular physical activity increased CD4 cells, salivary immunoglobulin IgA, and decreased neutrophil count compared to controls, all of which are components of a mounted immune response (1). Acute physical exercise has also been shown to increase natural killer cell cytolytic activity for 1-2 hours post-activity despite previously found suppression of natural killer cells after sports-related physical activity (2).

In an RCT (randomized controlled trial) examining the effects of exercise on sedentary elderly populations, CD3+, CD4+, and CD8+ T cells and IL-10 were increased and the CD4/CD8 ratio was decreased in the group participating in aerobic exercise compared to the group assigned to resisted exercise training (4). Another small RCT looking at the effects of moderate-intensity aerobic exercise on COVID-19 infection indicated that 2 weeks of aerobic exercise decreased the severity and progression of disease and increased circulating leucocytes, lymphocytes, and immunoglobulin A (5). In high-risk populations such as patients with breast cancer undergoing chemotherapy, physical activity did not negatively impact cellular immunity further than chemotherapy already had, although more studies are needed in subpopulations such as these (3).

Let’s break this down a little further. The evidence points at improved immune functioning in healthy individuals leading to decreased risk of infection, but there is also the relationship between regular exercise and decreased incidence of chronic metabolic conditions, which put people at higher risk of severe infection in the first place (1). Therefore, there may be protective value in both regular exercise over the long run and in frequent bouts of physical activity, which have been shown to increase innate and adaptive components of the immune system. In many of these studies, aerobic exercise (walking, running, swimming, cycling) at moderate or vigorous intensity made the biggest difference, although any form of exercise is better than none (1, 2, 4, 5).

The data suggests that regular exercise may be safe and may even be of benefit in higher-risk populations (3, 4). It may also benefit recovery during mild to moderate upper respiratory infections, as seen in many cases of COVID-19 (5). A word of caution here - it’s recommended that you listen to your body and slow down when you need to since rest is also integral to the recovery process. Bottom line: 150 min of aerobic exercise per week is the general recommendation for health maintenance and disease prevention in healthy adults, and now it may also help you stay healthy this cold and flu season. Please continue good hand hygiene and physical distancing when necessary, and always speak to your doctor before starting a new exercise regimen since some exercises are not safe for everyone.

Author: Emily Howard, ND, BSc

1. Chastin SFM, Abaraogu U, Bourgois JG, et al. Effects of Regular Physical Activity on the Immune System, Vaccination and Risk of Community-Acquired Infectious Disease in the General Population: Systematic Review and Meta-Analysis. Sports Med. 2021;51(8):1673-1686. doi:10.1007/s40279-021-01466-1
2. Rumpf C, Proschinger S, Schenk A, et al. The Effect of Acute Physical Exercise on NK-Cell Cytolytic Activity: A Systematic Review and Meta-Analysis. Sports Med. 2021;51(3):519-530. doi:10.1007/s40279-020-01402-9
3. Schmidt T, Jonat W, Wesch D, et al. Influence of physical activity on the immune system in breast cancer patients during chemotherapy. J Cancer Res Clin Oncol. 2018;144(3):579-586. doi:10.1007/s00432-017-2573-5
4. Abd El-Kader SM, Al-Shreef FM. Inflammatory cytokines and immune system modulation by aerobic versus resisted exercise training for elderly. Afr Health Sci. 2018;18(1):120-131. doi:10.4314/ahs.v18i1.16
5. Mohamed AA, Alawna M. The effect of aerobic exercise on immune biomarkers and symptoms severity and progression in patients with COVID-19: A randomized control trial. J Bodyw Mov Ther. 2021;28:425-432. doi:10.1016/j.jbmt.2021.07.012

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