IMMUNITY
Diet can support your body’s defense system
If you already exercise regularly, congratulations! You already do something to boost your immune system.
However, intense and prolonged exercise can temporarily impair our immunity.
It is also possible to just improve and support our immune system by eating the right things regularly.
Supplementation might be needed in some cases.
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Article links:
The immune response to heavy exercise and the potential role of diet
Nutrition and athletes’ immunity
The relationship between nutrition and immunity is deep and complex, and still under study. But research has demonstrated they influence each other: nutrition impacts immunity, and immunity has an effect on our bodies’ response to some foods. Furthermore, we have to account for demographics, environmental and lifestyle factors, which impact our immunity. Highly active endurance athletes are the most susceptible to developing upper respiratory tract infections after a race (see my article on the immune response to heavy exercise).
Generally, a diet rich in whole grains, diverse fruits and vegetables, beans, legumes, fermented dairy, eggs, including healthy fats, should provide enough nutrients to nurture our immunity.
In a nutshell, micronutrients associated with immune support are: Vitamins A, C, D, E, B6, B9 and B12 , Iron, Zinc, Copper and Selenium. Amino acids (from protein) are also very important as they provide the building blocks for immune cells and signaling molecules, and sufficient omega-3s -6s intake will help to fight inflammation.
So let’s make sure to get enough amino acids (from whole foods rich in protein) and sufficient omega-3s, such as from fatty fish, or seeds (chia, flaxseed), avocados, nuts, or even DHA-EPA supplements if you are vegan.
The fiber from a diet rich in fruits, mushrooms, fresh vegetables, and wholegrains will help our gut bacteria to stay healthy and protect us from pathogens. The polyphenols in berries, dark green vegetables, dark chocolate (that is good news !), and even coffee beans will provide natural antioxidants to fight inflammation.
Vitamin D: should we supplement?
Especially during the winter months, when exposure to sunlight is limited and if fatty fish are not consumed quite regularly, it is recommended to supplement with D3. Also, it is important to be aware that, as we age, our body's ability becomes less effective in the active form of vitamin D from sunlight.
Keep hydrated! Adequate hydration (depending on the individual, activity level, and seasons can vary extensively), but around 30-35ml/kg/BW is a good base to stay healthy.
In conclusion, there is no magic trick, but a nutrient rich-whole foods diet seems the way to go, which should bring all essential micro and macronutrients to nurture our immune system.
Calder, P.C. 2022. Foods to deliver immune-supporting nutrients. Current Opinion in Food Science. 10.1016/j.cofs.2021.12.006
Govers, C., Calder, P.C, Savelkoul, H.F.J., Albers, R., & van Neerven, R.J.J. 2022. Ingestion, Immunity, and Infection: Nutrition and Viral Respiratory Tract Infections. Frontiers in Immunology. 10.3389/fimmu.2022.841532
Murni, I.K, Prawirohartono, E.P, & Triasih, R. 2021. Potential Role of Vitamins and Zinc on Acute Respiratory Infections Including Covid-19. Global Pediatric Health. 10.1177/2333794X211021739
Venter, C., Eyerich, S., Sarin, T., & Klatt, K.C. 2020. Nutrition and the Immune System: A Complicated Tango. Nutrients. 10.3390/nu12030818
The immune response to heavy exercise and the potential role of diet
Highly active endurance athletes are the most susceptible to developing upper respiratory tract infections (URTI) after a long race (a marathon or an ultra-trail race), based on the theory that the immune system is weakened, referred to as “immunodepression”. Numerous studies have been conducted since the early 1990s on the topic of prolonged and strenuous exercise-induced inflammation and acute illness in endurance athletes.
There is a general consensus that the regular practice of low to moderate regular exercise is beneficial to health, by enhancing immunosurveillance, a process in which cells of the innate immune system look and recognise pathogens, even precancerous or cancerous cells in the body (Campbell and Turner, 2018; Nieman and Wentz, 2018; Simpson et al., 2020, Kurowski et al., 2022).
However, the impact of acute and prolonged exercise on athletes’ immune function is still an area of ongoing debate, with controversial results. The two widely accepted theories in exercise immunology are the “open-window” theory, in which the immune system is temporarily down-regulated, and the “J-curve and S-curve models”. The “J-curve model” applies to highly active recreational or professional athletes. As the S-curve is more observed in elite professional athletes, as an immune ability to withstand the impact of heavy exercise, either by genetics or stronger adaptation of the immune system.
Either way, athletes of all levels have a habit of using not only food to sustain their health, but also dietary supplements (DS). DS is a broad term, encompassing a diversity of functional foods, sports foods, macro and micronutrients. Diversity in type, dosage and frequency poses a challenge for research on their impact on athletes’ health. In their review on the prevalence of DS use amongst athletes worldwide, Daher, Mallick and El Khoury (2022) observed that the main reasons for DS were for “improving athletic performance, health, and accelerating recovery”, with females choosing to supplement more for health reasons, and males for performance. Some of them come in the form of sports foods, such as carbohydrate-rich drinks, gels, gummies, energy bars, protein bars or powder, BCAAs, electrolytes, creatine, or even caffeine.
A whole food balanced diet, and adequate calorie intake are obvious ways of supporting the immune system before and after heavy exercise. However, the use and impact of DS on URTI or inflammation of the airways have shown controversial results in research so far.
The immune response to heavy exercise has been recognised as “multifactorial”: immunity history and background play an important role (diagnosed allergy, easiness of catching a cold during the colder months, autoimmune condition). Prophylactic measures such as good hygiene have been pointed out in the scientific literature as a way to prevent URTI incidence, along with getting enough sleep and recovery, and stress level management.
Adequate carbohydrate intake, in the form of energy DS (which is usually the main DS consumed by athletes during races or prolonged exercise), has demonstrated protective effects against exercise-induced URS incidence and severity. High-quality protein (containing all essential amino acids), consumed post-exercise, promotes recovery and also building blocks for our immune cells and signalling molecules.
Acute inflammation is a normal part of training adaptation and immune response to exercise-induced stress. As long as the body has enough tools (in the form of nutrients such as antioxidants, and macronutrients to refuel and repair, the risk of developing illness post exercise is low.
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Campbell, J.P. and Turner, J.E. 2018. Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan. Frontiers in Immunology. 10.3389/fimmu.2018.00648
Cicchella, A., Stefanelli, C. and Massaro, M. (2021). Upper Respiratory Tract Infection in Sport and the Immune System response: A Review. Biology. https://doi.org/10.3390/biology10050362.
Daher, J., Mallick, M. and El Khoury, D. 2022. Prevalence of Dietary Supplement Use among Athletes Worldwide: A Scoping Review. Nutrients. 10.3390/nu14194109.
Kurowski, M., Seys. S., Bonini, M., Del Giacco, S., Delgado, L., Diamant, Z., Kowalski, M.L., Moreira, A., Rukhadze, M. and Couto, M. 2021. Physical exercise, immune response, and susceptibility to infections - current knowledge and growing research areas. Allergy, 2653-2664. 10.1111/all.15328.
Nieman, D. C., Henson, D. A., Dumke, C. L., Lind, R. H., Shooter, L.R. and Gross, S.J. 2006. Relationship between salivary IgA secretion and upper respiratory tract infection following a 160-km race. Journal of Sports Medicine and Physical Fitness. https://www.proquest.com/docview/202716211/fulltextPDF/F5B153F5D0964A80PQ/1?accountid=14548&sourcetype=Scholarly%20Journals
Nieman, D.C. and Wentz, L.M. 2019. The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science. doi.org/10.1016/j.jshs.2018.09.009.
Nieman, D.C, Lila, M.A. and Gillitt, N.D. 2019. Immunometabolism: A Multi-Omics Approach to Interpreting the Influence of Exercise and Diet on the Immune System. Annual Review of Food Science and Technology. 341-363.10.1146/annurev-food-032818-121316
Simpson, R.J., Campbell, J.P., Gleeson, M., Krüger, K., Nieman, D.C., Pyne, D.B., Turner, J.E. and Walsh, N.P. 2020. Can exercise affect immune function to increase susceptibility to infection? Exercise Immunology Review. http://eir-isei.de/2020/eir-2020-008-article.pdf