Vitamin C and COVID-19 infection

Vitamin C, also called ascorbic acid, is an essential micronutrient for humans. Deficiency of this vitamin results in impaired immunity and higher susceptibility to infections. It contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune systems.

Supplementation with ascorbic acid appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary ascorbic acid intakes that provide at least adequate, if not saturating plasma levels (i.e., 100-200 mg/day), which optimise cell and tissue levels. 

Vitamin C showed antiviral effects against influenza virus. In this regard, this vitamin may act against the influenza virus, coronavirus, or picornavirus. Ascorbic acid also has a beneficial effect in common cold, asthma and pneumonia. In a study, Citrus sinensis extract (rich in ascorbic acid) was found to inhibit the replication of coronavirus in infected cultured cells.

Ascorbic acid is the vastly taken vitamin by humans as it is found in various foods and sold as a dietary supplement. Due to its water solubility, dietary excesses not absorbed, and excesses in the blood rapidly excreted in the urine, so it exhibits remarkably low acute toxicity. But large doses of vitamin C may cause nausea, abdominal cramps and diarrhoea. Therefore, it is recommended to meet the nutrient requirement from natural food sources as much as possible and not overdose on it to avoid the unwanted effects.