Vitamin C, also known as ascorbic acid isvery important in the normal functioning of the immune system. Vitamin C is involved in an extensive range of biochemical pathways and participates in the innate and adaptive immune system. It is an effective antioxidant, protecting the neutrophils from oxidative stress in the early stages of an immune response, as neutrophils activate phagocytosis and produce reactive oxygen species (ROS) to destroy antigens.

Common cold is the most prevalent viral upper respiratory tract infections (URTI), which is characterized by sore throat, cough, tiredness and muscle pain, persisting for a period of few days to 3 weeks. Despite the symptoms being mild, the common cold is a foremost cause of absenteeism from work and school.

The rapid spread of SARS-CoV2 i.e. COVID-19 infection worldwide and the subsequent pandemic emergency that is recognized by the World Health Organization requires a global effort to identify high risk patients, treat symptoms and reduce deaths. At present, there is no specific antiviral treatment approved for COVID-19.

Sepsis is a life-threatening organ dysfunction that is caused due to impaired host response to infection. It is characterized by failure of the metabolic, circulatory and immune systems. It is also recognized as the main cause of death from infection, especially in patients developing septic shock with hospital mortality rates of up to 50%. In these clinical conditions, literature studies have shown that high doses of vitamin C by intravenous infusion might reduce the inflammatory cytokine-related production and improve important outcomes such as the mortality rates and duration of mechanical ventilation time.

Vitamin C homeostasis is regulated by at least four mechanisms such as intestinal absorption, transport to tissue, renal reuptake and urine excretion. It is primarily regulated by a family of proteins named Sodium-Dependent Vitamin C Transporters (SVCT). Studies have suggested that in healthy individuals, a daily intake of vitamin C from 100 to 400 mg guarantees 100% of the bioavailability and blood saturation with a steady state of plasma concentration reaching a maximum level of around 70–80 µmol/L.

Kim et al. had conducted a large randomized, placebo-controlled, double-blindtrial in 1,444 Korean soldiers. Out of them, 695 received vitamin C (6 g/day) for almost 30 days. The study showed that the vitamin C group had a 0.80-fold lower risk of catching the common cold as compared to the placebo group (n = 749).

In the Ran et al. randomized trial, the combination of a small and long-term regular dose of vitamin C (not more than 1 g/day) sustains immunity and a larger dose of vitamin C supplementation during the onset of the common cold (3–4 g/day) was related with relieve in chest pain, reduction of fever and chills, reduction in the indoor-stay duration and the mean duration of disease.

Several data have emerged regarding the use of vitamin C through intravenous administration (IA). Recently, thein fusion of vitamin C has been suggested to treat COVID-19 in ICU hospitalized patients. In COVID-19 patients, the inflammatory response is very sudden and is defined as a “cytokine storm”, which is associated with increased plasma concentration of IL-2, IL-1β, IL-6, IL-10, IFNγ, and TNF-α resulting in ARDS that requires urgent ICU interventions.

There are two studies by Fowler et al. that are currently available on IA of vitamin C in ICU hospitalized patients and inflammatory response. In the first preliminary study, vitamin C has shown a significant reduction in proinflammatory biomarkers (i.e. CRP and procalcitonin) in the first 96 hours, without any adverse effects registered during the infusion, but the number of ARDS-affected patients treated was too small.

In the second large study, 167 patients with sepsis and ARDS were randomized to take vitamin C (50 mg/kg every 6 h for 96 h) or placebo. There were no changes in CRP and thrombomodulin were detected. It reported a lower duration of mechanical ventilation support in the vitamin C group, with a higher number of ventilator-free days in the vitamin C group as compared to the placebo group (10.6 vs. 13.1 days, respectively).

Vitamin C supplementation might be effective for improving the health status of patients who are considered at high risk of viral infections such as in obesity, diabetes mellitus, chronic lung diseases and cardiovascular diseases.

Intravenous administration of vitamin C could be an adjuvant therapy to rapidly restore plasma levels of vitamin C during severe sepsis and ARDS in ICU hospitalized patients.

Source: Cerullo G, Negro M, Parimbelli M, et al. The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19. Front Immunol. 2020;11:574029. Published 2020 Oct 28. doi:10.3389/fimmu.2020.574029