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Electronic Journal of General Medicine
2021, 18(5), em311
e-ISSN: 2516-3507
https://www.ejgm.co.uk/ Letter to the Editor OPEN ACCESS
Current Evidence on Vitamin C, D, and Zinc Supplementation for
COVID-19 Prevention and/or Treatment
Andrea Giacalone
1*
, Luca Marin
2
, Massimiliano Febbi
2
, Marcos Roberto Tovani-Palone
3**
1
University of Rome Tor Vergata, Department of Industrial Engineering, Rome, ITALY
2
Asomi College of Sciences, Department of Research, Marsa, MALTA
3
Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, BRAZIL
*Corresponding Author: giacalonericci@yahoo.it
**Corresponding Author: marcos_palone@hotmail.com
Citation: Giacalone A, Marin L, Febbi M, Tovani-Palone MR. Current Evidence on Vitamin C, D, and Zinc Supplementation for COVID-19 Prevention
and/or Treatment. Electron J Gen Med. 2021;18(5):em311. https://doi.org/10.29333/ejgm/11099
ARTICLE INFO
ABSTRACT
Received:
5 Jun. 2021
Accepted:
11 Jul. 2021
In
this article, we discuss current evidence on some of the dietary supplements that have been most
commonly
used
for coronavirus disease 2019 (COVID-19) prevention and/or treatment, including vitamin C, vitamin D,
and
zinc
.
Keywords: COVID-19, pandemics, ascorbic acid, vitamin D, zinc
Dear Editor,
The role of food sources immune-boosting nutrients has
been much discussed during the coronavirus disease 2019
(COVID-19) pandemic. Moreover, a nutritional deficiency could
be a predisposing factor to development and progression of a
viral infection [1]. However, there is still no global consensus
regarding the use of dietary supplements and/or medicines in
the recommendations for COVID-19 management [2,3].
Knowledge of the benefits and risks associated with the use of
dietary supplements is of considerable importance, especially
if they are used in order to prevent and/or treat severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) infection
cases. In this context, pharmacists should ensure that patients
are informed of the current lack of evidence to demonstrate the
effectiveness of dietary supplements for that purpose [4]. Here,
we discuss some of the dietary supplements that have been
most commonly used for COVID-19 prevention and/or
treatment, including vitamin C, vitamin D, and zinc.
VITAMIN C
Vitamin C has a number of physiological properties and its
intravenous use is believed to be effective in inhibiting
cytokines production in acute respiratory distress syndrome
cases [5]. Vitamin C properties include its acting as an
enzymatic cofactor and antioxidant factor, roles in
proteoglycan deglycanation, in the free radicals scavenger
process, histone dealkylation, and homeostasis of subcellular
compartments [6]. Some clinical trials have looked at the use
of vitamin C as part of a respiratory diseases management plan
[7]. Recently, a team of Chinese doctors stated that they have
effectively treated over 50 patients affected by mild to acute
COVID-19 with large intravenous (IV) vitamin C doses (10,000-
20,000 mg/d) for a period of 8-10 hours [8]. In fact, vitamin C has
modes of action that could be relevant to acute respiratory
infections management, such as antioxidant, anti-
inflammatory, antithrombotic, and immunomodulatory
functions [9]. However, it should be borne in mind that high
doses of vitamin C can promote the development of kidney
stones, especially in people with high oxalate levels [4].
In addition, surprisingly, in an open randomized clinical
trial conducted in Pakistan, the use of standard therapy in
combination with IV vitamin C resulted in early regression of
COVID-19 symptoms and reduced length of hospital stay [10].
In contrast, other studies performed in the USA show that
vitamin C treatment caused no change in COVID-19 patients
[11,12]. It should be noted that the results of many ongoing
randomized clinical trials are still pending and currently
available studies do not provide scientifically strong evidence
for the use of vitamin C as a treatment for COVID-19.
VITAMIN D
Vitamin D obtained by sun exposure, food, and
supplements must undergo two hydroxylation reactions to be
converted into calcitriol (the biologically active form of vitamin
D) [13]. Maintaining sufficient vitamin D levels through
adopting a healthy diet, consuming vitamin supplements, and
sun exposure is essential for good health. Patients should
carefully follow the guiding principles for daily vitamin D intake
based on: maximum intake levels to optimize general health
and a need for intake due to vitamin deficiency. It is
recommended to follow medical advice and avoid doses higher
than the upper limit (4000IU/day; 100µg/day) in the hope of
treating or preventing COVID-19 [14]. Prolonged intake of more
2 / 3 Giacalone et al. / ELECTRON J GEN MED, 2021;18(5):em311
than 4000 IU of vitamin D is considered to be potentially
dangerous and may cause hypercalcemia [4].
On the other hand, given the possible association between
hypovitaminosis D and COVID-19, vitamin D supplementation
has been indicated as a useful treatment due to its anti-
inflammatory and antithrombotic properties [15]. Vitamin D
deficiency appears to be associated with more severe clinical
stages of COVID-19, so its assessment may be a useful analysis
for possible therapeutic interventions [16]. However, the use of
high doses of vitamin D does not significantly reduce the
mortality rate or length of stay [17].
ZINC
Administration of zinc lozenges has been associated with a
reduction in the duration and severity of cold symptoms. In this
case, zinc should be administered within 24 hours of symptoms
development, at doses around 80 mg/day and for less than two
weeks [18-20]. Zinc supplementation increases mucociliary
clearance, anti-oxidative effects, and epithelial integrity.
Furthermore, it decreases viral replication and the likelihood of
hyperinflammation, as well as maintains antiviral immunity,
reducing lung damage and the risk of secondary infections [21].
In this regard, zinc combined with medicines could eventually
be effective in COVID-19 patients only if administered prior to
the onset of the cytokine storm [22].
FINAL CONSIDERATION
Current COVID-19 treatment recommendations make no
mention of dietary supplements and do not include the use of
drugs not tested in clinical trials [23,24]. Although the use of
dietary supplements has created high expectations in the
population, there is no robust evidence in the literature
supporting the effectiveness of their use for COVID-19
prevention and/or treatment.
Author contributions: All authors have sufficiently contributed to the
study, and agreed with the results and conclusions.
Funding: No funding source is reported for this study.
Declaration of interest: No conflict of interest is declared by authors.
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