Scott W. Tunis MD FACS •
"I’ve heard that strenuous and endurance exercise can suppress the immune system.
I’m a runner. Should I be worried about greater susceptibility to infection?
What nutritional strategies should I adopt to optimize my immune system?"
These are great questions, especially in the setting of the COVID-19 virus pandemic.
As a dedicated recreational athlete, you are eager to continue your training regimen while also being diligent to observe social distancing guidelines. After all, you want to be ready for that rescheduled race in the fall, right?
But you are probably also concerned about maintaining optimum immunity and resistance to infection. Your concerns about strenuous exercise causing a reduction in immunity are real, particularly with respect to upper respiratory infections.
Keep in mind, COVID-19 starts as an upper respiratory tract infection (URTI).
Several studies, such as the “Risk of Upper Respiratory Tract Infection in Athletes: An Epidemiologic and Immunologic Perspective” published in the Journal of Athletic Training, which examined 27 years of epidemiologic data concluded the following:
- Endurance athletes are at increased risk for URTI during periods of heavy training and the 1-to 2-week period after marathon-type race events.
- Following each bout of prolonged heavy endurance exercise, several components of the immune system appear to demonstrate suppressed function for several hours.
- There appears to be an “open window,” described as the 3- to 72-hour time period after prolonged endurance exercise when host defense is decreased and the risk of URTI is elevated.
Exactly how common is URTI in athletes? Very common. It is the most common reason for non-injury-related presentation to sports medicine clinics, accounting for 35-65% of illness presentations.
Interestingly, a study in Medicine and Science in Sports and Exercise found a higher rate of URTI among elite athletes than in recreationally competitive athletes. So it would seem the faster you run, the more vulnerable you are. (Maybe there is some benefit to us back-of-the-packers!)
Which in part, has led us to the understanding that different levels of intensity and duration of exercise can lead to different, and even opposite, effects on the immune system.
So what should we be doing?
As a starting point, there is no substitute for sensible approaches that help maintain immunity and health, including eating a healthy diet, maintaining normal body weight, minimizing mental stress, avoiding overtraining, getting adequate sleep, controlling chronic illness, and practicing good hygiene.
With respect to nutrition, consuming adequate carbohydrates and protein commensurate with the level, intensity and duration of exercise are the single most important nutritional determinants of insuring proper immune function.
Evidence also suggests the elements Iron, Zinc, and Magnesium, the anti-oxidants Quercetin and Curcumin, and the amino acids L-Theanine and Glutamine play roles in supporting the immune response in athletes. There are, of course, a myriad of other vitamins, minerals, and micronutrients which may also play significant roles in supporting immune function in athletes, and for which the clinical investigations are ongoing.
The field of Exercise Immunology is a rapidly evolving specialty and is the subject of a great deal of research. The more we know about how the various the types, intensities, and durations of exercise can affect our immune system, and the more we know about how certain nutrients can modulate our immune response, the better training plans and nutritional strategies we will have.
In the meantime, do the simple things like eat well, sleep soundly, and recover adequately. If your diet is not perfect, consider supplementation for which there is sound data supporting the benefit of the ingredients. And above all stay safe, and stay well.
Remember, we are all in this together… for the Long Run.