From The Desk Of Kordel's Scientist cum Senior Pharmacist, Dr. Lum.

A recent study published in JAMA Network Open, a reputable journal, hit the headlines of major newspapers. The study was done in Ohio and Florida on 214 outpatients who were diagnosed with SARS-CoV-2 infection. Patients were randomized into 4 groups, each group allocated to one of 4 treatments given for 10 days: (a) vitamin C 8000mg daily in 2-3 divided doses   (b) zinc gluconate 50mg (c) both vitamin C 8000mg and zinc gluconate 50mg (d) usual care only, with no study medications. Results showed that active treatment with vitamin C, zinc gluconate or both did not have significant effects on the duration of Covid-19 symptoms compared to usual care (Thomas et al 2021).

Before we jump to the conclusion on the futility of taking vitamin C and zinc supplements, let us put things in the right perspective. Vitamin C and zinc given in the study were intended for treatment, after confirmed infection of SARS-CoV-2. These micronutrients, while being essential for optimum immune protection particularly against viral and bacterial infections, are not appropriate for acute treatment. On the contrary, vitamin C and zinc are best taken on a regular basis to maintain adequate levels in the body so that the immune cells are well-equipped to destroy pathogenic organisms that may enter our body at any time. Adequate levels of vitamin C and zinc (as well as other micronutrients) are necessary for immune health, but there is no evidence to show that very high doses would increase immune function to beyond its normal health status.

On account of its potent anti-oxidant properties, vitamin C levels are rapidly depleted in the presence of infections or other acute stress conditions. A study revealed that vitamin C levels in hospitalized patients with Covid-19-associated acute respiratory distress had low levels of vitamin C (Chiscano-Camon et al 2020), likely due to increased metabolic utilization to neutralize free radicals generated by inflammation. It is now well-established that the critical phase during Covid-19 infections is the excessive release of pro-inflammatory cytokine and chemokines and subsequent multiple organ failure. Thus, having adequate levels of vitamin C right from the start of infection will help mitigate this “cytokine storm” and confer protection against oxidative injury. Administering high doses of vitamin C after initiation of the cytokine storm is akin to fighting a blazing flame with a hand-held fire extinguisher.  

Similarly, zinc is required for development and maturation of immune cells, and plays an important role in anti-oxidant reactions. Covid-19 patients were more likely to have lower zinc serum levels compared to healthy individuals. Moreover, Covid-19 patients who were zinc-deficient developed more complications, longer hospital stay and increased mortality compared to those who were not (Joachimiak 2021; Jothimani et al 2020). These observations point to an important role for zinc in human immune health and enhancing resistance to SARS-CoV-2 infections. Again, taking high doses of zinc over short-term is unlikely to have the same beneficial effects of maintaining adequate levels in the long term with regard to promoting healthy immune function.

Given the effectiveness of vitamin C and zinc in reducing the duration, severity and frequency of cold and flu symptoms (Wintergerst et al 2006; Maggini et al 2012), and the observed low serum levels of these micronutrients in Covid-19 patients, it is prudent to recommend preventive supplementation of these two supplements as an affordable and safe way to reduce the risk of Covid-19 infections and to improve clinical outcomes in mild cases.

In summary, we believe that regular supplementation with vitamin C and zinc is vital for optimum health protection, not forgetting the importance of other micronutrients such as vitamin D and vitamin K as well. In particular, elderly individuals often have compromised micronutrient levels, and they are also highly susceptible to SARS-CoV-2 infections (Cabrera 2015). Appropriate supplementation is also indicated in individuals with co-morbidities.

It is important to note that these and other dietary supplements are intended for prophylaxis and not for treatment purposes. If you show positive signs and symptoms of Covid-19, you are strongly advised to seek appropriate medical help.



1. Thomas S, Patel D, Bettel B at al (2021) Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection. The COVID A to Z Randomized Clinical Trial. Jama Network Open 4:e210369 doi:10.1001/jamanetworkopen.2021.0369.


2. Joachimiak MP (2021). Zinc against COVID-19? Symptom surveillance and deficiency risk groups.
PLOS Neglected Tropical Diseases |


3. Wintergerst ES, Maggini S, Hornig DH (2006). Immune-enhancing role of vitamin C and zinc and effect on clinical conditions. Annals Nutr Metab 50:85–94


4. Chiscano-Camón L, Ruiz-Rodriguez JC, Ruiz-Sanmartin A, et al (2020). Vitamin C levesl in SARS-CoV-2 associated acute respiratory distress syndrome. Critical Care 24:522


5. Crebera AJR (2015). Zinc, aging and immunosenescence: an overview. Pathobiology of Ageing and Age-Related Diseases 5: 25592.