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Vitamin C utilisation in 2020: have we bought a lemon?
  1. Robert Marcec1,
  2. Fran Posavec1,
  3. Robert Likic1,2
  1. 1 University of Zagreb Medical School, Zagreb, Croatia
  2. 2 Department of Internal Medicine, Clinical Pharmacology Unit, Clinical Hospital Centre Zagreb, Zagreb, Croatia
  1. Correspondence to Dr Robert Likic; robert.likic{at}

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The SARS-CoV-2 pandemic drastically impacted our everyday lives and while vaccines were (and some still are) in development, various medicines and supplements were suggested for repurposing, although mostly with no or with limited success. Among proposed over-the-counter (OTC) substances, vitamin C (ascorbic acid) stood out as it was widely available, affordable, safe and used (with more or less success) in the past for the prevention and treatment of respiratory infections in the population.

Today’s popularity of vitamin C use in respiratory infections can be linked to the 1970s when the Nobel prize laureate Linus Pauling popularised his theory that vitamin C can be used prophylactically against the common cold and that it can ameliorate its symptoms. As vitamin C is an essential micronutrient and antioxidant required for a broad range of biological processes, its proposed beneficial effect in respiratory infections is not really that farfetched. Vitamin C has been demonstrated to have beneficial in vitro effects on multiple immune cells. Notably, it can accumulate in phagocytic cells and amplify phagocytosis, chemotaxis, generation of reactive oxygen species (ROS) and ultimately enhance the antimicrobial activity of phagocytes. The role of vitamin C in lymphocytes is not fully explained, but it has been shown to enhance the proliferation and differentiation of both T and B lymphocytes, possibly due to an effect on gene regulation. It also supports epithelial barrier functioning and assists the oxidant scavenging in the skin, thus potentially protecting against environmental oxidative stress.1 Although the rationale behind the use of vitamin C in respiratory infections is sound and it is well known that vitamin C deficiency results in impaired immunity and higher susceptibility to infections, results …

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  • Contributors RM and RL conceived the idea and conducted the data analysis. FP wrote the first draft. All authors contributed to writing the final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.