Since the beginning of the COVID-19 pandemic, good doctors have done what good doctors do and have given their patients safe and effective therapeutics to treat COVID-19.
While public health officials said nothing could be done, many doctors applied lessons learned from previous viral infections and helped their patients support their immune systems with safe measures that have a known history.
Common measures suggested by those doctors have included the use of vitamin D and antioxidants. As the pandemic wears on, mounting evidence points to the efficacy of many of these treatments, including quercetin.
Statistical Improvement in Clinical OutcomesTwo recent studies highlight the potential this safe plant-derived antioxidant has to treat COVID-19.
The quercetin was used with sunflower lecithin, which has been demonstrated to increase absorption in the gut by as much as 20 times, compared to pure quercetin formulations.
The main outcomes being evaluated were virus clearance and symptoms. After one week of treatment, 16 of the 21 patients in the quercetin group tested negative for SARS-CoV-2 and 12 reported that all of their symptoms had diminished.
In the standard care group, only two patients tested negative and four reported partially improved symptoms. By the end of week two, the five remaining patients in the quercetin group tested negative. In the standard care group, 17 of the 19 remaining patients tested negative and one had died.
Can Quercetin Reduce Hospitalizations and Deaths?The second study—a prospective, randomized, and controlled open-label trial—gave 152 COVID-19 outpatients a daily dose of 1,000 mg of quercetin for 30 days to evaluate its adjuvant effects in the treatment of early COVID-19 symptoms and the prevention of severe infection.
“The results revealed a reduction in frequency and length of hospitalization, in need of non-invasive oxygen therapy, in progression to intensive care units and in a number of deaths,” the study authors wrote.
“The results also confirmed the very high safety profile of quercetin and suggested possible anti-fatigue and pro-appetite properties.”
Mechanisms of ActionThe authors of the first study wrote that they chose quercetin because it has antiviral, anti-blood clotting, anti-inflammatory, and antioxidant properties, all of which are important in the treatment of SARS-CoV-2 infection. In the second study, more detailed mechanisms of action are reviewed.
“Quercetin is characterized by three crucial properties: antioxidant, anti-inflammatory and immunomodulatory. The combination of these actions allows quercetin to be a potential candidate to support all unhealthy conditions where oxidative stress, inflammation and immunity are involved,” they wrote.
Initially, quercetin gained attention because it’s a zinc ionophore, meaning it shuttles zinc—which has well-known antiviral effects—into your cells just like the drug hydroxychloroquine.
Some proposed that the primary reason hydroxychloroquine and quercetin worked was because of this feature. Of course, you also had to take zinc along with either of them. To effectively act as a zinc ionophore, quercetin also needs vitamin C.
Since then, other studies, including the two reviewed in this article, have shown that quercetin has other actions that make it useful against SARS-CoV-2 as well. As reported by Murray in his newsletter:
“In particular, quercetin exerts significant inhibition on the binding of specific spike proteins to ACE-2 receptors, thereby blocking the ability of the virus to infect human cells. Quercetin has also been shown to directly neutralize viral proteins that are critical in the replication of SARS-CoV-2.”
Quercetin’s Antiviral PropertiesQuercetin’s antiviral properties have been attributed to three main mechanisms of action: inhibiting the virus’ ability to infect cells; inhibiting replication of already infected cells; and reducing infected cells’ resistance to treatment with antiviral medication.
Quercetin Works Against Many Common VirusesBefore the COVID-19 pandemic struck, several studies had highlighted quercetin’s ability to prevent and treat the common cold (which is often caused by a coronavirus) and seasonal influenza. By attenuating oxidative damage, quercetin also lowers your risk of secondary bacterial infections, which is actually the primary cause of influenza-related deaths.
How Quercetin Combats Inflammation and Boosts ImmunityAside from its antiviral activity, quercetin is also known for boosting immunity and combating inflammation. A 2016 study in the journal Nutrients describes the mechanisms of action, which included inhibiting a cytokine involved in systemic inflammation, dampening the production of inflammation-producing enzymes, and curbing other inflammatory agents.
BioavailabilityWhile quercetin does have potent antiviral effects, in order for it to work effectively, you need sufficiently high dosages to raise the level of quercetin in your body’s tissues. The relatively low absorption rate of quercetin is why a sunflower lecithin formulation was used.
“Since both of these forms of quercetin produce similar blood levels, they should produce the same effects at equal dosages based upon quercetin content,” Murray wrote in his newsletter.
“My dosage recommendation as part of a nutritional supplement program to support immune function is 250 mg twice daily.
“And in patients with active infection, my recommendation is ... six capsules twice a day providing a total of 3,000 mg of quercetin. This high dosage should be taken for at least 10 days and then reduced to a maintenance dosage of 250 mg twice daily.