Can Quercetin Have an effect on COVID Outcomes?


In an August 21, 2021, e-newsletter,1 Dr. Michael Murray mentioned the usage of quercetin for respiratory an infection signs. In November 2020, he’d suffered a “very delicate and temporary bout of COVID-19.” 

He additionally recounts an anecdotal story of a buddy who developed suspicious respiratory signs. His buddy had been taking quite a few dietary supplements stated to supply safety, however was nonetheless feeling terrible.

Because it seems, the one factor he’d not taken was quercetin, and as quickly as he did, that very same day, his signs began to dissipate. This expertise, Murray says, “is in line with the outcomes from two medical trials” that have been not too long ago printed.

Quercetin appears to be a secure, far inexpensive, and easier-to-obtain and it really works by an analogous mechanism, driving zinc into the cells to cease viral replication.

Statistical Enchancment in Medical Outcomes

Within the first research,2 42 COVID-19 outpatients have been divided into two teams. One group of 21 sufferers acquired commonplace medical remedy consisting of analgesics and an antibiotic (acetaminophen 500-milligram (mg) to 1,000-mg dose if physique temperature was increased than 37.5 levels C — 99.5 F — with a most day by day dosage of three grams, and 500 mg azithromycin for 3 consecutive days).

The opposite group of 21 sufferers acquired commonplace remedy plus the equal of 600 mg of quercetin per day (divided into three doses) for seven days, adopted by one other seven-day course of 400 mg of quercetin per day (divided into two doses).

The quercetin was used with sunflower lecithin, which has been demonstrated to extend absorption within the intestine by as a lot as 20 occasions, in comparison with pure quercetin formulations.

The primary outcomes being evaluated have been virus clearance and signs. After one week of therapy, 16 of the 21 sufferers within the quercetin group examined unfavourable for SARS-CoV-2 and 12 reported that every one signs had diminished.

In the usual care group, solely two examined unfavourable and 4 had partially improved signs. By the tip of Week 2, the 5 remaining sufferers within the quercetin group examined unfavourable. In the usual care group, 17 of the 19 remaining sufferers examined unfavourable and one had died.

“These outcomes are spectacular and hopefully extra research can be carried out on hospitalized sufferers to see how quercetin is perhaps useful in additional extreme instances,” Murray wrote in his e-newsletter.

Can Quercetin Cut back Hospitalizations and Deaths?

The second research3 — a potential, randomized, managed and open-label trial — gave 152 COVID-19 outpatients a day by day dose of 1,000 mg of quercetin for 30 days to guage its adjuvant results within the therapy of early signs and the prevention of extreme an infection. Based on the authors:

“The outcomes revealed a discount in frequency and size of hospitalization, in want of non-invasive oxygen remedy, in development to intensive care items and in variety of deaths. The outcomes additionally confirmed the very excessive security profile of quercetin and prompt attainable anti-fatigue and pro-appetite properties.

QP (Quercetin Phytosome®) is a secure agent and together with commonplace care, when utilized in early stage of viral an infection, might support in bettering the early signs and assist in stopping the severity of COVID-19 illness. It’s prompt {that a} double-blind, placebo-controlled research ought to be urgently carried out to substantiate the outcomes of our research.”

Mechanisms of Motion

As famous within the first research4 above, quercetin was chosen based mostly on the truth that it has antiviral, anti-blood clotting, anti-inflammatory and antioxidant properties, all of that are vital within the therapy of SARS-CoV-2 an infection. Within the second research, extra detailed mechanisms of motion are reviewed. Based on the authors:5

“SARS-CoV-2 proteases, like 3-chymotrypsin-like protease (3CLpro), papain-like pro-tease (PLpro), RNA-dependent RNA polymerase, spike (S)protein and human angiotensin-converting enzyme 2 (hACE2) are thought-about attainable targets for growing efficient anti-COVID-19 medicine.

Lately, molecular docking research have prompt the attainable binding interplay of quercetin with the 3CLpro, PLpro, and S-hACE2 complicated. Some current outcomes, obtained by biophysical methods, seem to help the outcomes of the molecular docking research.

Quercetin, a flavonol not naturally current within the human physique, is essentially the most ample polyphenol in fruits and vegetable and is extensively used as a dietary complement to spice up the immune system and promote a wholesome way of life.

Quercetin is characterised by three essential properties: antioxidant, anti-inflammatory and immunomodulatory. The mix of those actions permits quercetin to be a possible candidate to help all unhealthy circumstances the place oxidative stress, irritation and immunity are concerned.”

Initially, quercetin gained consideration as a result of it’s a zinc ionophore, that means it shuttles zinc — which has well-known antiviral results — into your cells similar to the drug hydroxychloroquine.

Some proposed the first cause hydroxychloroquine and quercetin labored was due to this function. After all, you additionally needed to take zinc together with both of them. To successfully act as a zinc ionophore, the quercetin additionally wants vitamin C.

Since then, different research, together with the 2 reviewed right here, have proven quercetin has different actions that makes it helpful in opposition to SARS-CoV-2 as effectively. As reported by Murray in his e-newsletter:

“Specifically, quercetin exerts important inhibition on the binding of particular spike proteins to ACE-2 receptors, thereby blocking the power of the virus to contaminate human cells. Quercetin has additionally been proven to instantly neutralize viral proteins the are important within the replication of SARS-CoV-2.”

In some research, quercetin has additionally been proven to inhibit the discharge of inflammatory cytokines, which might assist alleviate infection-related signs and suppress extreme inflammatory responses from occurring. Its antioxidant results might also assist forestall tissue harm attributable to scavenging free radicals, thereby aiding within the restoration technique of viral infections.6

Quercetin’s Antiviral Properties

Quercetin’s antiviral properties have been attributed to 3 essential mechanisms of motion:

  1. Inhibiting the virus’ capability to contaminate cells
  2. Inhibiting replication of already contaminated cells
  3. Decreasing contaminated cells’ resistance to therapy with antiviral medicine

For instance, analysis7 funded by the U.S. Protection Superior Analysis Tasks Company (DARPA), printed in 2008, discovered it lowers your danger of viral sickness comparable to influenza and boosts psychological efficiency following excessive bodily stress, which could in any other case undermine your immune operate and render you extra inclined to infections.

Right here, cyclists who acquired a day by day dose of 1,000 mg of quercetin together with vitamin C (which reinforces plasma quercetin ranges8,9) and niacin (to enhance absorption) for 5 weeks have been considerably much less prone to contract a viral sickness after bicycling three hours a day for 3 consecutive days, in comparison with untreated controls. Whereas 45% of the placebo group obtained sick, solely 5% of the therapy group did.

Quercetin Works Towards Many Widespread Viruses

Earlier than the COVID-19 pandemic struck, a number of research had highlighted quercetin’s capability to forestall and deal with the widespread chilly and seasonal influenza.10,11,12,13,14,15,16,17,18 By attenuating oxidative harm, it additionally lowers your danger of secondary bacterial infections,19 which is definitely the first reason for influenza-related deaths.

Importantly, quercetin will increase mitochondrial biogenesis in skeletal muscle, which suggests a part of its antiviral results are because of enhanced mitochondrial antiviral signaling.20 Quercetin additionally works in opposition to different viruses, as demonstrated within the following research:

A 1985 research discovered quercetin inhibits infectivity and replication of herpes simplex virus kind 1, polio-virus kind 1, parainfluenza virus kind 3 and respiratory syncytial virus (RSV).21

A 2016 animal research22 discovered quercetin inhibited mouse dengue virus and hepatitis virus.

Different research have confirmed quercetin’s energy to inhibit each hepatitis B23 and C24 an infection.

A March 2020 research25 discovered quercetin gives “complete safety” in opposition to Streptococcus pneumoniae an infection, each in vitro and in vivo, primarily by neutralizing pneumolysin (PLY),26 one of many toxins launched from pneumococci that encourages S. pneumoniae an infection to blossom within the first place.

Streptococcus pneumoniae is accountable not just for pneumonia, however will also be concerned in some ear and sinus infections, meningitis and sure blood infections.27 As reported by the authors of this research:28

“The outcomes indicated that quercetin considerably lowered PLY-induced hemolytic exercise and cytotoxicity by way of repressing the formation of oligomers.

As well as, therapy with quercetin can scale back PLY-mediated cell damage, enhance the survival charge of mice contaminated with a deadly dose of S. pneumoniae, alleviate the pathological harm of lung tissue and inhibit the discharge of cytokines (IL-1β and TNF-α) in bronchoalveolar lavage fluid.

Contemplating the significance of those occasions in antimicrobial resistant S. pneumoniae pathogenesis, our outcomes indicated that quercetin could also be a novel potential drug candidate for the therapy of medical pneumococcal infections.”

How Quercetin Combats Irritation and Boosts Immunity

Apart from its antiviral exercise, quercetin can also be recognized for reinforcing immunity and combating irritation. As famous in a 2016 research29 within the journal Vitamins, mechanisms of motion embrace (however isn’t restricted to) the inhibition of:30

  • Lipopolysaccharide (LPS)-induced tumor necrosis issue α (TNF-α) manufacturing in macrophages. TNF-α is a cytokine concerned in systemic irritation, secreted by activated macrophages, a kind of immune cell that digests overseas substances, microbes and different dangerous or broken parts
  • LPS-induced mRNA ranges of TNF-α and interleukin (IL)-1α in glial cells, which ends up in “diminished apoptotic neuronal cell loss of life”
  • The manufacturing of inflammation-producing enzymes
  • Calcium inflow into the cell, which in flip inhibits pro-inflammatory cytokine launch, in addition to histamine and serotonin launch from intestinal mast cells31

Based on this paper, quercetin additionally stabilizes mast cells, has cytoprotective exercise within the gastrointestinal tract, and “a direct regulatory impact on primary practical properties of immune cells,” which permits it to inhibit “an enormous panoply of molecular targets within the micromolar focus vary, both by down-regulating or suppressing many inflammatory pathways and capabilities.”32


Whereas quercetin does have potent antiviral results, to ensure that it to work successfully you want sufficiently excessive dosages to lift the extent of quercetin in your physique’s tissues.

The comparatively low absorption charge of quercetin is why a sunflower lecithin formulation was used.

Analysis33 printed within the July-December 2021 concern of the Journal of Pure Well being Merchandise Analysis, discovered a quercertin matrix has the identical whole absorption charge as quercetin phytosome — and better peak blood ranges.

“Since each of those types of quercetin produce related blood ranges, they need to produce the identical results at equal dosages based mostly upon quercetin content material,” Murray wrote in his e-newsletter, including:

“My dosage advice as a part of a dietary complement program to help immune operate is 250 mg twice day by day.

And in sufferers with energetic An infection, my advice is … six capsules twice a day offering a complete of three,000 mg of quercetin. This excessive dosage ought to be taken for at the very least 10 days after which lowered to a upkeep dosage of 250 mg twice day by day …

[This] excessive dosage is probably not vital. However my dosage calculations are based mostly upon doubtless tissue concentrations wanted to exert the strongest antiviral results. And given the security of quercetin, there is no such thing as a hurt at this degree.”

Protocol Utilizing Quercetin

One physician who early introduced quercetin into the limelight was Dr. Vladimir Zelenko. As hydroxychloroquine grew to become troublesome to acquire, Zelenko switched to recommending quercetin as a substitute, because it’s available as an over-the-counter complement. For a downloadable “cheat sheet” of Zelenko’s protocol for COVID-19, go to

Different Well being Advantages of Quercetin

There are additionally different lesser recognized advantages and makes use of for quercetin, together with the prevention and/or therapy of:34


Heart problems37

Weight problems38 and metabolic syndrome39 (a cluster of circumstances together with hypertension, excessive blood sugar, excessive triglyceride ranges and fats accumulation across the waist that elevate your danger for Sort 2 diabetes, coronary heart illness and stroke)

Sure sorts of most cancers, specifically leukemia, and to a lesser diploma breast most cancers40

Nonalcoholic fatty liver illness (NAFLD)41



Temper issues44

Aluminum-induced neurodegenerative modifications, comparable to these seen in Alzheimer’s, Parkinson’s and amyotrophic lateral sclerosis (ALS).45

Longevity, due to its senolytic advantages (clearing out broken and worn-out cells)46,47

Analysis has additionally highlighted quercetin’s epigenetic affect and talent to:48

  • Work together with cell-signaling pathways
  • Modulate gene expression
  • Affect the exercise of transcription components
  • Modulate microRNAs

MicroRNAs was once thought-about “junk” DNA. However removed from being ineffective, analysis has revealed so-called “junk” DNA is definitely microRNA and performs an important position in regulating genes that make the proteins that construct your physique.

The microRNA operate as “on/off” switches for the genes. Relying on the microRNA enter, a single gene can code for any of greater than 200 protein merchandise. Quercetin’s capability to module microRNA might also assist clarify its cytotoxic results, and why it seems to enhance most cancers survival (at the very least in mice).