As COVID-19 cases spike again in many areas, some cities are bringing back masks, and public health officials are considering more widespread measures. Yet as we shared in a recent post, there are some simple things your athletes can do to boost their immunity, including prioritizing sleep, keeping protein intake high, and combining submaximal endurance and strength training.
Another of the most underrated ways for your athletes to protect themselves against COVID is to ensure they’re consuming a well-balanced diet and supplementing when necessary. In this article, we’ll explore how micronutrient status can directly correlate with lowering the risk of infection and potentially reducing the severity of symptoms if your athletes do get sick.
Micronutrients and Immune Function
Vitamins and minerals are involved in many functions pertaining to your clients’ performance, including energy metabolism, muscle contraction and cardiovascular output. What your athletes might not know is that these micronutrients also play a crucial role in immunity and might help reduce the risk of them contracting COVID-19 and speed their recovery if they get it. The authors of a report released via the British Journal of Nutrition stated:
Many of the risk factors identified so far that are related to viral infections and deaths from COVID-19 have underlying associations with nutritional status and specific essential nutrients that are known to contribute to the normal functions of the immune system.
Important nutrients that support the immune function include vitamins A and D, the B vitamins (folate, vitamins B6 and B12) and vitamin C, and the minerals and trace elements Zn [zinc], Fe [iron], Se [selenium] and Cu [copper]. Deficiencies and suboptimal nutritional status of these micronutrients can potentially decrease resistance to infections and reinfections.[i]
They went on to advocate for a diet full of fruit and vegetables, which are rich sources of such micronutrients. Yet a growing body of evidence suggests that many people aren’t getting enough of the vitamins and minerals needed to support a strong immune response to COVID-19, influenza and other viruses and infections. This creates an opportunity for immunonutrition, i.e., using certain nutrients to optimize immune function. All of the vitamins and minerals mentioned in the British Journal of Nutrition paper are crucial to your clients’ immunity.
Still, we’ll focus on those that have been correlated with COVID incidence, severity, and duration in peer-reviewed studies.
Vital Vitamins for Immunity
An Israeli study published in PLOS ONE found that patients with a vitamin D deficiency were 14 times more likely to have a severe or critical case of COVID-19. The authors also noted that the mortality rate among vitamin D deficient patients was 25.6%, compared to just 2.3% for those with sufficient vitamin D levels.[ii] Another group of researchers examined how vitamin D fights COVID infection in the “International Journal of Molecular Sciences.” It supports innate immunity by activating receptor cells that modulate the appropriate response to the virus, trigger the creation of more antimicrobial peptides and stimulate the release of enzymes that break down viral particles.
“Regarding adaptive immunity, vitamin D enhances CD4+ T cells, suppresses T helper 17 cells, and promotes the production of virus-specific antibodies by activating T cell-dependent B cells,” the authors added.[iii] It might also prevent the body from overreacting to infection with a cytokine storm that can cause more damage to the respiratory system.
Your athletes have probably heard this advice umpteen times before, but as the Environmental Protection Agency estimates that the average American adult spends 93% of their time indoors, it bears repeating: the easiest way to boost vitamin D levels – not to mention accessing stress-busting and circadian rhythm-stabilizing benefits – is to get out in sunlight with some skin exposed for at least 20 minutes a day.
If your clients live somewhere that isn’t very sunny, they’ll still get some D from training, walking or even just sitting outdoors, but they might need to supplement, particularly when fall turns into winter. In this case, combining vitamin D in its D3 form with vitamin K can increase its absorption and bioavailability.
The role of high-dose vitamin C in treating COVID cases remains controversial, but there is evidence that low levels of it are correlated with increased incidence of the virus and greater severity of symptoms. Testing of adult patients admitted to the ICU at Pujol University Hospital in Barcelona, Spain found that 82% had low vitamin C levels. The study’s authors stated that vitamin C promotes phagocytosis during infection, whereby immune cells engulf and digest viral particles. The vitamin also aids the transport of leucocytes, white blood cells that attack unknown organisms.[iv] It also supports the protective function of the epithelial barrier in the lungs, which, when compromised, can lead to COVID-related breathing dysfunction.
A second Spanish study found that vitamin C levels were so low in 90% of hospitalized COVID patients that they were undetectable. They suggested one possible explanation was “increased metabolic consumption due to the enhanced inflammatory response.” [v] This makes sense, given the many immune functions involved in vitamin C, which also include clearing out dead cells to reduce tissue damage, determining which immune cells should respond to a virus, and transporting neutrophils and macrophages to infection sites.
Your athletes can up their vitamin C intake with a wide range of fruit and vegetables, including kiwi, blackcurrants, strawberries, kale, broccoli, and bell peppers. Supplementation shouldn’t be needed, but if a client feels under the weather, they could take 500 to 1,000 mg of liposomal vitamin C, which is more readily absorbed.
Mighty Immunity-Supporting Minerals
Similarly to the Israeli research, a South Korean study of patients hospitalized with COVID found that 76% were deficient in vitamin D. They also noted that 42% were low in selenium. This mineral – which is classed as “essential” because your body cannot make its own – is vital for cellular immunity, particularly the healthy function of T and natural killer (NK) cells that neutralize infection.
The authors stated that “there is an association between infection severity and T-cell and NK cell dysfunction,” which might explain why selenium deficiency could compromise the ability to fight off COVID and other viruses.[vi] Rich dietary sources of selenium include red meat, salmon, eggs, sunflower seeds and Brazil nuts. If one of your athletes is considering supplementing too, advise them to only take a low level of 50 to 100 mcg, as anything over 400 total can be harmful.
Zinc is another mineral that’s vital to healthy immune function. A meta-analysis of 33 prior studies that investigated possible links between COVID-19 infection and micronutrient status found two papers in which patients had low zinc levels. [vii] The first noted that at Sakai City Medical Center in Japan, “almost all severe cases showed subclinical or clinical zinc deficiency.”[viii] The meta-analysis also cited an Indian study that found people were 239% more likely to be hospitalized for more than a week with COVID if they had low zinc levels.
The authors highlighted the “potent immunoregulatory and antiviral properties” of zinc, which is involved in over 200 immunomodulatory and antioxidant reactions, maturation of innate and adaptive immune cells and the ability of T and B cells to detect and respond to infection.[ix] Animal sources of zinc include oysters, lamb and chicken. If any of your clients are vegetarian or vegan, they can top up with avocados, lentils, and sprouted whole grains.
It would be foolish to suggest that micronutrients can prevent your clients from contracting COVID-19 or any other illness. However, it is clear from the evidence discussed above that avoiding deficiency in vitamins C and D and minerals like zinc and selenium should be a key consideration as you encourage them to eat a well-balanced diet that supports not only performance and recovery but also immune function.
Resources
[i] David P Richardson and Julie A Lovegrove, “Nutritional Status of Micronutrients as a Possible and Modifiable Risk Factor for COVID-19: A UK Perspective,” British Journal of Nutrition, August 20, 2020, available online at https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/nutritional-status-of-micronutrients-as-a-possible-and-modifiable-risk-factor-for-covid19-a-uk-perspective/35B4C4BC5B0FBD132370128EC03FE309#.
[ii] Amiel A Dror et al, “Pre-Infection 25-Hydroxyvitamin D3 Levels and Association with Severity of COVID-19 Illness,” PLOS ONE, February 3, 2022, available online at https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0263069.
[iii] Ming-Yieh Peng et al, “Immunological Aspects of SARS-CoV-2 Infection and the Putative Beneficial Role of Vitamin-D,” International Journal of Molecular Sciences, May 2021, available online at https://pubmed.ncbi.nlm.nih.gov/34065735.
[iv] Teresa Maria Tomasa-Irriguible and Lara Bielsa-Berrocal, “COVID-19: Up to 82% Critically Ill Patients Had Low Vitamin C Values,” Nutrition Journal, July 9, 2021, available online at https://nutritionj.biomedcentral.com/articles/10.1186/s12937-021-00727-z.
[v] Luis Chiscano-Camón et al, “Vitamin C Levels in Patients with SARS-CoV-2-Associated Acute Respiratory Distress Syndrome,” Critical Care, August 26, 2020, available online at https://ccforum.biomedcentral.com/articles/10.1186/s13054-020-03249-y#author-information.
[vi] Jae Hyoung Im et al, “Nutritional Status of Patients with COVID-19,” International Journal of Infectious Diseases, November 2020, available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418699/#bib0125.
[vii] Min Xian Wang et al, Nutrients, “Micronutrients Deficiency, Supplementation and Novel Coronavirus Infections—A Systematic Review and Meta-Analysis,” May 2021, available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8151981.
[viii] Yukako Yasui et al, “Analysis of the Predictive Factors for a Critical Illness of COVID-19 During Treatment － Relationship Between Serum Zinc Level and Critical Illness of COVID-19,” International Journal of Infectious Diseases, November 2020,available online athttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC7476566.
[ix] Dinesh Jothimani et al, “COVID-19: Poor Outcomes in Patients with Zinc Deficiency,” International Journal of Infectious Diseases, November 2020, available online at https://pubmed.ncbi.nlm.nih.gov/32920234/.
