How These Key Nutrients are Linked to COVID-19 Severity
Nutrition is a critical part of optimizing your immune system to fight off viruses like COVID-19 and keep you healthy. But what about if you do get sick? In this article, we dive into the science behind how our nutrition status can help protect ourselves against developing severe symptoms and even potentially support the treatment of patients in hospitals.
Vitamin C is essential for various key elements of our immune defence against viruses. Studies have shown that Vitamin C can help the body recover faster from upper respiratory tract infections.1 In addition, one study reported that up to 82% of critically ill COVID-19 patients had low Vitamin C plasma levels (<0.4 mg/dL).2 While this is only correlational data, it suggests that Vitamin C could play an important role in preventing critical illness in COVID-19 patients.
It is proposed that Vitamin C’s role in reducing the inflammatory response helps protect the lungs from injury and subsequent sepsis (widespread infection that can be highly fatal).3 High doses of intravenous Vitamin C have even been used in certain countries as part of the treatment protocol for hospitalized COVID-19 patients and on-going trials are taking place to evaluate the role of high-dose IV vitamin C in COVID-19 treatment.4
Like Vitamin C, glutathione is a potent antioxidant that helps modulate inflammation, especially in times of viral infection. During infection with COVID-19, the body’s immune cells attack the invading virus, creating large amounts of oxidative stress. It is then the job of antioxidants to neutralize it before it damages the surrounding tissues. As the master antioxidant of the body, glutathione deficiency results in amplified oxidative stress due to compromised antioxidant defenses.
One research study compared glutathione levels and oxidative stress in uninfected individuals versus hospitalized COVID-19 patients of all age groups. They found that the COVID-19 patients had severe glutathione deficiency, increased oxidative stress and elevated oxidant damage. These levels were particularly surprising in younger age groups, who naturally have higher glutathione levels.5 Another similar study concluded, “elevated levels of oxidative stress and reduction of antioxidant indices can aggravate disease’s severity in hospitalised patients with COVID-19”.6
As glutathione declines with age,7 this correlation becomes even more pronounced in older patients, which could be a contributing factor for why COVID-19 can be more serious in older patients.
Vitamin D receptors are found on every type of cell in the body. This means that its role is so multifaceted it’s been linked to almost every health outcome. Interest in its role in immunity has been widespread ranging from autoimmune diseases, to cancer, to viral infections.
In a ground-breaking 2021 study, researchers evaluated the effectiveness of Vitamin D3 supplementation as an acute treatment protocol for COVID-19 patients. When they took all the patients with low Vitamin D levels (25OHD <30 ng/m), they found that patients without the Vitamin D3 supplementation had a 1.9-fold increased risk of having hospitalization longer than 8 days compared to those who did receive supplementation. Even more impressive was that treatment with Vitamin D decreased the mortality rate 2.14 times compared to those who didn’t receive Vitamin D, even in the presence of comorbidities.8
Scientists are still figuring out the mechanisms of actions (theories include Vitamin D’s role in preventing anemia, regulating inflammation, preventing sepsis, stimulating immune pathways and more), but the researchers went so far as to state that Vitamin D supplementation is “essential for COVID-19 treatment”.8
Selenium is an essential trace mineral found in soil. As with so many minerals, depleted soil can lower the levels of selenium in our produce, increasing the risk of deficiency. Despite being needed in small amounts, selenium is essential for immunity – it is involved in regulating oxidative stress, redox, and other crucial cellular processes, including those involved in innate and adaptive immune responses.9
In a large study from China involving 14,045 COVID-19 cases, fatality rates in selenium-deficient areas were 2.7 times higher than areas without selenium deficiency.10 Although this correlation is based on the selenium content of the soil, it does warrant further research into how selenium can reduce COVID-19 fatalities and improve treatment outcomes.
N-acetyl-cysteine (NAC) has been shown to support the recovery of respiratory diseases, through antioxidant and anti-inflammatory actions.11 As a precursor of glutathione, NAC has been used to loosen thick mucus in the lungs, boost the immune system, suppress viral replication, and reduce inflammation.12 Oral NAC (1200 mg/d) in patients with COVID-19 pneumonia reduced the risk for mechanical ventilation and mortality, even in severe cases.11
In a larger cohort study, IV NAC significantly improved disease conditions in severe respirator-dependent COVID-19 patients. IV NAC appeared to work on multiple pathways to reduce inflammatory markers, such as C-reactive protein (CRP) and ferritin, and also improve lung functions.13
- Vorilhon P, Arpajou B, Vaillant Roussel H, Merlin É, Pereira B, Cabaillot A. Efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection. A meta-analysis in children [retracted in: Eur J Clin Pharmacol. 2021 Jun;77(6):941]. Eur J Clin Pharmacol. 2019;75(3):303-311. doi:10.1007/s00228-018-2601-7
- Tomasa-Irriguible, T.M., Bielsa-Berrocal, L. COVID-19: Up to 82% critically ill patients had low Vitamin C values. Nutr J20, 66 (2021). https://doi.org/10.1186/s12937-021-00727-z
- Fisher BJ, Kraskauskas D, Martin EJ, et al. Mechanisms of attenuation of abdominal sepsis induced acute lung injury by ascorbic acid. Am J Physiol Lung Cell Mol Physiol. 2012;303(1):L20-L32. doi:10.1152/ajplung.00300.2011
- gov. Vitamin C Infusion for the Treatment of Severe 2019-nCoV Infected Pneumonia. https://clinicaltrials.gov/ct2/show/NCT04264533.
- Premranjan Kumar, Ob Osahon, David B. Vides, Nicola Hanania, Charles G. Minard, Rajagopal V. Sekhar. Severe Glutathione Deficiency, Oxidative Stress and Oxidant Damage in Adults Hospitalized with COVID-19: Implications for GlyNAC (Glycine and N-Acetylcysteine) Supplementation. Antioxidants, 2021; 11 (1): 50 DOI: 3390/antiox11010050
- Karkhanei B, Talebi Ghane E, Mehri F. Evaluation of oxidative stress level: total antioxidant capacity, total oxidant status and glutathione activity in patients with COVID-19. New Microbes New Infect. 2021;42:100897. doi:10.1016/j.nmni.2021.100897
- Samiec PS, Drews-Botsch C, Flagg EW, et al. Glutathione in human plasma: decline in association with aging, age-related macular degeneration, and diabetes. Free Radic Biol Med. 1998;24(5):699-704. doi:10.1016/s0891-5849(97)00286-4
- Gönen MS, Alaylıoğlu M, Durcan E, et al. Rapid and Effective Vitamin D Supplementation May Present Better Clinical Outcomes in COVID-19 (SARS-CoV-2) Patients by Altering Serum INOS1, IL1B, IFNg, Cathelicidin-LL37, and ICAM1. Nutrients. 2021;13(11):4047. Published 2021 Nov 12. doi:10.3390/nu13114047
- Hoffmann PR, Berry MJ. The influence of selenium on immune responses. Mol Nutr Food Res. 2008;52(11):1273-1280. doi:10.1002/mnfr.200700330
- Zhang, HY., Zhang, AR., Lu, QB. et al.Association between fatality rate of COVID-19 and selenium deficiency in China. BMC Infect Dis 21, 452 (2021). https://doi.org/10.1186/s12879-021-06167-8
- Assimakopoulos SF, Aretha D, Komninos D, et al. N-acetyl-cysteine reduces the risk for mechanical ventilation and mortality in patients with COVID-19 pneumonia: a two-center retrospective cohort study. Infect Dis (Lond). 2021;53(11):847-854. doi:10.1080/23744235.2021.1945675
- Shi Z, Puyo CA. N-Acetylcysteine to Combat COVID-19: An Evidence Review. Ther Clin Risk Manag. 2020;16:1047-1055. Published 2020 Nov 2. doi:10.2147/TCRM.S273700
- Ibrahim H, Perl A, Smith D, et al. Therapeutic blockade of inflammation in severe COVID-19 infection with intravenous N-acetylcysteine. Clin Immunol. 2020;219:108544. doi:10.1016/j.clim.2020.108544
Rachel Erwin, Nutritionist & Content Writer
Rachel is a Nutritionist with a BSc in Biology and Global Health from the University of Toronto, and a Postgraduate Diploma in Human Nutrition from the University of Ulster. She has counselled and educated clients in Hong Kong, whose health goals ranged from weight loss to detox and hormone balancing. Her love of writing led her to complete ‘Writing in the Sciences’, offered by Stanford University, and since then she has contributed several evidence-based health articles to various publications.