Vitamin C and COVID-19: A Evaluation

Vitamin C, also called ascorbic acid, is an essential water-soluble nutrient. Humans and some other animals such as primates and pigs are dependent on vitamin C from the food supply through fruits and vegetables (peppers, oranges, strawberries, broccoli, mangoes, lemons). The potential role of vitamin C in preventing and relieving infections is well known in medicine.

Ascorbic acid is critical to immune responses. It has important anti-inflammatory, immunomodulatory, antioxidant, antithrombotic, and antiviral properties.

Vitamin C appears to favorably modulate the host’s responses to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic, especially in the critical stages. In a review recently published in Preprints *, Patrick Holford et al. Address the role of vitamin C as adjunct therapy in respiratory infections, sepsis and COVID-19.

This article discusses the potential role of vitamin C in preventing the critical phase of COVID-19, acute respiratory infections, and other inflammatory diseases. Vitamin C supplementation could show promise as a preventive or therapeutic agent for COVID-19 – to correct a disease-related deficiency, reduce oxidative stress, increase interferon production, and support the anti-inflammatory effects of glucocorticosteroids.

To maintain a normal plasma level of 50 µmol / l in adults, a vitamin C dose of 90 mg / d for men and 80 mg / d for women is required. This is enough to prevent scurvy (a disease resulting from a lack of vitamin C). However, this level is not sufficient to prevent virus exposure and physiological stress.

Therefore, the Swiss Nutrition Society recommends a supplement of 200 mg vitamin C for everyone to close the nutrient gap for the general population and especially for adults aged 65 and over. This supplement is said to boost the immune system. ‘

Vitamin C and immune response

A rapid decrease in the vitamin C level in human serum is observed under physiological stress conditions. A serum level of vitamin C ≤ 11 µmol / l is found in hospital patients – most of them suffer from acute respiratory infections, sepsis or severe COVID-19.

Various case studies from around the world show that low vitamin C levels are typical in critically ill hospital patients with respiratory infections, pneumonia, sepsis and COVID-19 – the most likely explanation is increased metabolic consumption.

A meta-analysis highlights these observations: 1) the risk of pneumonia is significantly reduced by vitamin C supplementation, 2) post-mortem studies in COVID-19 deaths show a secondary pneumonia phenomenon and 3) cohorts with pneumonia of 62% with hypovitaminosis C..

Mechanism of action of vitamin C.

Vitamin C plays an important homeostatic role as an antioxidant. It is known to show direct virucidal activity and increase interferon production. It has effector mechanisms in both the innate and adaptive immune systems. Vitamin C reduces reactive oxidative species (ROS) and inflammation by weakening NF-κB activation.

While SARS-CoV-2 downregulates the expression of type 1 interferons (the host’s primary antiviral defense mechanism), ascorbic acid upregulates these important host defense proteins.

Relevance of Vitamin C for COVID-19

The critical and often fatal phase of COVID-19 occurs with the overproduction of potent proinflammatory cytokines and chemokines. This leads to the development of multiple organ failure. It is associated with the migration and accumulation of neutrophils in the pulmonary interstitium and bronchioalveolar space – a key determinant of ARDS (acute respiratory distress syndrome).

Ascorbic acid concentrations in the adrenal glands and pituitary gland are three to ten times higher than in any other organ. Under conditions of physiological stress (ACTH stimulation), including exposure to viruses, vitamin C is released from the adrenal cortex, which leads to a five-fold increase in plasma levels.

Vitamin C increases cortisol production and potentiates the anti-inflammatory and endothelial cytoprotective effects of glucocorticoids. Exogenous glucocorticoid steroids are the only proven treatment for COVID-19. Vitamin C, a pleiotropic stress hormone, plays a crucial role in mediating the adrenocortical stress response, especially in sepsis, and in protecting the endothelium from oxidant damage.

Colds are caused by over 100 different strains of the virus, some of which are coronaviruses.

Given the effects of vitamin C on colds – reduced duration, severity, and number of colds – administration of vitamin C may reduce the conversion from a mild infection to the critical phase of COVID-19.

Vitamin C supplementation has been observed to shorten the length of stay in the intensive care unit, reduce ventilation time in critical COVID-19 patients, and reduce mortality in sepsis patients who require vasopressor treatment.

Vitamin C dosage

The authors discuss the safety of oral and intravenous administration of vitamin C considering the various scenarios of diarrhea, kidney stones, and kidney failure at high dosages. A safe, short-term high dose of 2-8 g / day can be recommended (caution in people with a history of kidney stones or kidney disease due to high doses). Because the dose is often water-soluble and thus excreted within hours, it is important to maintain adequate blood levels during an active infection.


Vitamin C is known to prevent infections and improve the immune response. With special consideration of the critical phase of COVID-19, vitamin C plays a crucial role. It downregulates the cytokine storm, protects the endothelium from oxidant damage, plays an essential role in tissue repair and improves the immune response against infections.

Vitamin C shows promising results when administered to the seriously ill.

The authors recommend that people in risk groups for COVID-19 mortality and the risk of vitamin C deficiency receive daily vitamin C supplementation. You should ensure the adequacy of vitamin C at all times and increase the dose up to 6-8 g / day in the event of a viral infection. Several dose-dependent vitamin C cohort studies are ongoing worldwide to confirm its role in reducing COVID-19 and to better understand its role as therapeutic potential.

* Important NOTE

Preprints publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guide clinical practice / health-related behavior, or be treated as established information.

Journal reference:

  • Holford, P .; Carr, A .; Jovic, TH; Ali, SR; Whitaker, IS; Marik, P .; Smith, D. Vitamin C – An Add-On Therapy for Respiratory Infections, Sepsis, and COVID-19. Preprints 2020, 2020100407 (doi: 10.20944 / preprints202010.0407.v1).

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