With the Vancouver BMO marathon coming up in a few weeks, it is imperative that runners eat properly to maintain immune system strength. Current research has shown that marathoners are at an increased risk for upper respiratory tract infections after racing (Nieman, 2009). Anecdotally, this holds true as all the “weekend warrior” type of runners that I know oftentimes end up contracting colds after participating in marathons; I don’t see this as often in the high-level runners I know, which is probably due to better training, nutrition, or both.

Several mechanisms predispose marathoners to illness after a race.  Most obviously, poor training practices can lead to compromised immunity.  Overtraining syndrome is common among runners and results from improper periodization, insufficient recovery, sleep, and hydration, as well as macronutrient and micronutrient deficiencies; overtraining due to one, or all of these factors may compromise the immune system (Walsh, 2018).  In terms of nutrition, there are many ways in which athletes may step their game up in order to support optimal immune health.  Below, I’ve taken the liberty of reading through all the pertinent research and coming up with simple guidelines for you to eat and drink for immune system strength.

Dehydration can play a role in compromising marathoner immune function.  In one study, dehydrated athletes who lost ~3% of their bodyweight post-exercise showed decreases in markers of oral immune function.  These deficits in immune function may be exaggerated in marathoners who can lose up to 5% of their bodyweight (via fluid loss) within a single race (Zouhal et al., 2011).  So what do we do?

  • Aim to drink 3-4L of water on both training and rest days.
  • Estimate sweat loss by weighing yourself pre- and post-run.  For each kg of sweat lost, aim to drink 1.5L of a hypertonic solution of water, carbohydrates, and sodium (e.g. Gatorade).

Inadequate food intake can also compromise immune function.  Energy restriction and low energy availability is associated with increased incidence of illness (Walsh, 2018).  Specifically, low carbohydrate intake may cause immunosuppression in marathoners. Low carbohydrate intake can increase the stress response of exercise and impair immune cell function (Bermon, 2017).  Reduced blood glucose concentration may “starve” immune cells (e.g. phagocytes, neutrophils) and impair function (Bermon, 2017). So what do we do?

Iron Deficiency (ID), commonplace among endurance athletes (Parks et al., 2017), results from a variety of factors: low iron intake, foot strike hemolysis, and the upregulation of hepcidin post-exercise.    ID, or low iron levels is associated with compromised immunity (Hasan et al., 2016). Another micronutrient that is commonly deficient in runners, especially during winter months is vitamin D. Vitamin D is associated with an increased risk for upper respiratory tract infections (URTI) in athletes (He et al., 2013).  So what do we do?

  • See a doctor twice per year to have your serum ferritin levels (and indicator of iron status) checked.  Values below 35nmol/L are considered anemic, and your doctor may deem anything above 35nmol/L to be sufficient.  But really, due to the oxygen-carrying demands of marathon running, your values should be hovering around 60nmol/L.  Iron levels can be increased by eating iron rich foods such as spinach, red meat, and liver, or with iron supplementation.
  • Supplement with vitamin D during winter months.  1000-4000IU per day is the recommended dose by most sport dieticians.

Post-marathon illness is very common and is oftentimes due to a combination of poor training and inadequate nutrition.  In this article we only talked about the nutrition side of the equation, so please remember that no matter how well you eat, you still may be in big trouble if you are training poorly.  

To all the BMO marathon runners this year, I wish you the best of luck and as always, if you’d like to know more about, and start taking responsibility for your own health, fitness, and wellness, please reach out to Crux Fitness Richmond Gym for any of your personal training needs.

Patrick Koo – Personal Trainer at Crux Fitness Richmond

Crux Fitness is also in Cloverdale!

*Photo by Martins Zemlickis


Bermon, S. (2017). Consensus statement immunonutrition and exercise. Exercise Immunology Review, 23, 1077-5552.

Gleeson, M., & Bishop, C.B. (2000). Modification of immune responses to exercise by carbohydrate, glutamine, and anti-oxidant supplements. Immunology and Cell Biology 78, 554–561.

Gleeson, M. (2013). Nutritional support to maintain proper immune status during intense training. In Nutritional Coaching Strategy to Modulate Training Efficiency (Vol. 75, pp. 85-97). Karger Publishers.

Hassan, T.H., Badr, M.A., Karam, N.A., Zkaria, M., El Saadany, H.F., Abdel Rahman, D.M., He, C.S., Handzlik, M., Fraser, W.D., Muhamad, A., Preston, H., Richardson, A., & Gleeson, M. (2013). Influence of vitamin D status on respiratory infection incidence and immune function during 4 months of winter training in endurance sports athletes. Exerc Immunol Rev, 19, 86-101.

Nieman, D. C. (2009). Immune function responses to ultramarathon race competition. Med Sportiva, 13(4), 189-196.

Parks, R.B., Hetzel, S.J., & Brooks, M.A. (2017). Iron deficiency and anemia among collegiate athletes: A retrospective chart review. Medicine & Science in Sports & Exercise, 49(8), 1711-1715.

Peeling, P., Dawson, B., Goodman, C., Landers, G., Wiegerinck, E.T., Swinkels, D.W., & Trinder, D. (2009). Training surface and intensity: Inflammation, hemolysis, and hepcidin expression. Med Sci Sports Exerc, 41(5), 1138-1145.

Shahbah, D.A., Al Morshedy, S.M., Fathy, M., Esh, A.M.H., & Selim, A.M. (2016). Impact of iron deficiency anemia on the function of the immune system in children. Medicine, 95(47), e5395.

Walsh, N.P. (2018) Recommendations to maintain immune health in athletes. European Journal of Sport Science, 18(6), 820-831, DOI: 10.1080/17461391.2018.1449895.

Zouhal H., Groussard C., & Minter G. (2011). Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners. British Journal of Sports, 45(14), 1101-1105.

Zourdos, M. C., Sanchez-Gonzalez, M. A., & Mahoney, S. E. (2015). A brief review: the implications of iron supplementation for marathon runners on health and performance. The Journal of Strength & Conditioning Research, 29(2), 559-565.

Leave a Reply