The Importance of Quercetin and Zinc During Pandemic

Zinc provides immune support amongst other functions. Zinc inhibits coronavirus replication and is a general stimulant of antiviral immunity (source). Higher levels of intracellular zinc showed to increase intracellular pH; which affect on RNA-dependent RNA polymerase and decreases the replication mechanism of RNA viruses (e.g. COVID-19). 

For zinc to work effectively in the body to boost immune system function, zinc has to be pushed into the cells which would require an ionophore. An ionophore is a substance that transports particles across the cell wall barrier into the center of the cell.

Therefore, zinc ionophores (e.g. Quercetin) can likely be used with zinc supplement to act as antiviral against many RNA viruses including influenza and COVID-19. Suggested benefits of zinc supplementation along with zinc ionophores to prevent and treat COVID-19 and other respiratory tract infections are supported by countless studies (source). 

In most cases, prophylactic and early use of zinc supplementation was more effective than late therapeutic proceedings. Up to 30% of the everyday respiratory infections, briefly named “common cold,” are due to infections with coronaviruses. Studies showed reduced symptom severity, reduced frequency, and duration of the common cold after zinc administration depending on dosage, zinc compound and the start time after initial symptoms (source).

Zinc deficiency is very common especially in the elderly, diabetics, cancer patients, asthma, immunosuppressed and obese - all of which have higher levels of mortality for COVID-19. Furthermore, zinc deficiency is associated with increased risk of infectious disease, pneumonia and severity of COVID-19. Conversely, zinc supplementation is associated with a significant decrease in COVID-19 mortality as long as it is delivered with a zinc ionophore (source). 

In short, a balanced zinc homeostasis is essential. Zinc supplementation improves the mucociliary clearance, strengthens the integrity of the epithelium, decreases viral replication, preserves antiviral immunity, attenuates the risk of hyper-inflammation, supports anti-oxidative effects and thus reduces lung damage and minimizes secondary infections. Especially older subjects, patients with chronic diseases and most of the remaining COVID-19 risk groups would most likely benefit. 

Quercetin, a natural anti-oxidant, anti-inflammatory and anti-blood clot compound contained in abundance in various fruits and vegetables, is a zinc ionophore. Zinc ionophores help transport zinc inside the cells COVID-19 attacks - respiratory cells, providing significant antiviral action against COVID-19. 

Additionally, Quercetin has been shown to be a potent inhibitor of coronaviruses by inhibiting cellular entry as well as inhibiting proinflammatory cytokines. One of the hallmarks of COVID-19 is an imbalanced immune response cascading to cytokine storms and then hyper inflammation which then can lead to acute respiratory distress syndrome (ARDS). 

Quercetin has been shown to inhibit proinflammatory cytokine production as well as inflammation due to its antioxidant properties, amongst others. By inhibiting destructive inflammation and potentially the entire cascade, quercetin may prevent severe damage to the respiratory system amongst other organs (source). 

Recent clinical trial data shows that the combination of Vitamin C and Quercetin provided strong preventative protection against COVID-19 infection of healthcare workers when compared to the control group as shown below (source). Specifically, 1.4% (1 out of 71 healthcare workers) of healthcare workers using Quercetin and Vitamin C combination were infected with COVID-19 vs. 21.4% (9 out of 42 healthcare workers) of healthcare workers in the control group were infected with COVID-19 (Total Subjects, n = 113).

Elderberry, red onions, white onions, cranberries and green tea are among the richest sources of dietary quercetin.

As of September, 2021 there have been 4 published studies of quercetin against COVID-19. For the list of studies, check out

For clinical trials, more than 10 studies have been launched to investigate the benefits of quercetin against COVID-19. Ultimately, the results of the above trials will offer more definitive evidence.