The Substack Fashionable Discontent just lately posted an anthology sequence on the advantages of quercetin,1 together with the discovering that it really works like hydroxychloroquine, a drug discovered to be efficient towards SARS-CoV-2 when used early sufficient.

Half 12 begins with a short overview of what quercetin is and its primary mechanisms of motion. Quercetin is a flavonoid present in a wide range of vegatables and fruits, akin to onions and shallots, apples, broccoli, asparagus, inexperienced peppers, tomatoes, crimson leaf lettuce, strawberries, raspberries, blueberries, cranberries, black currants and inexperienced tea.

The quercetin content material in any given meals is basically depending on gentle publicity, although, so relying on the nation you’re in, completely different meals will high the checklist of most quercetin-rich. Basic mechanisms of motion of this nutrient embrace:3

Antioxidant exercise — Antioxidants assist stop oxidative injury from dangerous reactive oxygen species (ROS). Quercetin acts as a free radical scavenger, and its exercise might be additional enhanced by vitamin C

Anti-inflammatory exercise — That is partly liable for quercetin’s cardiovascular advantages

Inhibition of platelet aggregation

Anti-allergy actions (inhibits launch of histamine and different allergic substances)


Anticancer exercise

Antiviral exercise — It’s been discovered to scale back replication of many viruses, together with HIV, hepatitis C, enterovirus 71, porcine epidemic diarrhea virus and SARS-CoV-2, by concentrating on the proteases in these viruses

Zinc ionophore — Quercetin helps zinc enter your cells. Zinc, in flip, has potent antiviral exercise

Quercetin In opposition to SARS-CoV-2

In Half 24 of the anthology, Fashionable Discontent evaluations the proof behind the advice to make use of quercetin towards COVID-19 particularly. As talked about, zinc has antiviral exercise, and quercetin helps shuttle the zinc into the cell. However quercetin additionally has different mechanisms of motion that make it helpful within the combat towards COVID-19.

For instance, quercetin has been proven to:

Inhibit SARS-CoV-2 spike protein to ACE2 receptor docking.5,6,7 Computational modeling research have proven quercetin can bind to the ACE2 receptor and the spike protein interface, thereby inhibiting the 2 from binding collectively. By stopping viral attachment, it helps stop viral entry into the cell. Commenting on one in every of these research, Fashionable Discontent notes:8

“Though [a] pc modeled research,9 the proof right here means that quercetin’s binding exercise to ACE2 is akin to different customary of care medication used to deal with SARS-CoV-2 (eg. Remdesivir, Lopinavir, Ritonavir).”

Inhibit lipopolysaccharide (LPS)-induced tumor necrosis issue α (TNF-α) manufacturing in macrophages.10 (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.)

Inhibit the discharge of proinflammatory cytokines and histamine by modulating calcium inflow into the cell.11

Stabilize mast cells and regulate the essential purposeful properties of immune cells, thereby permitting 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.”12

Act as a zinc ionophore, i.e., a compound that shuttles zinc into your cells.13 This is likely one of the mechanisms that may account for the effectiveness seen with hydroxychloroquine, which can be a zinc ionophore.

Enhance interferon response to viruses, together with SARS-CoV-2, by inhibiting the expression of casein kinase II (CK2)14 — CK2 is an enzyme that’s basic to controlling homeostasis on the mobile stage. There’s proof that it down-regulates the power a cell has to generate Kind 1 interferon when attacked by a virus.

It does this by inhibiting retinoic acid-inducible gene I (RIG-I),15 which has protein sensors that sign genetic expression of sort 1 interferon by figuring out the replication of RNA viruses, akin to SARS-CoV-2. Quercetin inhibits the expression of CK2, which slows the replication of RNA viruses.16

Interferons are a subset of cytokines found in 1957.17 These cells are sometimes the preliminary protection towards viruses. There are two varieties and three types of interferon. Inside Kind 1 interferon, there are alpha and beta. Kind 2 interferon has the gamma kind.18

The different sorts are based mostly on the operate of the cytokine. Kind 1 interferons assist cells resist viruses. Kind 2 aids in responding to infections and most cancers progress. The identify “interferon” got here from the power of Kind 1 to intrude with the virus’s capability to duplicate. A cell secretes interferons when a overseas substance, like a virus, is detected.

Nevertheless, the interferon doesn’t operate by attacking the virus. As a substitute, it tells the contaminated cell and the cells that encompass the contaminated cell to make proteins that cease viral replication. In a nutshell, quercetin stops CK2 from interfering with the motion of Kind 1 interferon so cells obtain the sign to cease viral replication.

Modulate NLRP3 inflammasome, an immune system part concerned within the uncontrolled launch of proinflammatory cytokines that happens throughout a cytokine storm.19

Exert a direct antiviral exercise towards SARS-CoV20,21,22 — Quercetin’s basic antiviral capability has been attributed to 3 main mechanisms of motion:

  1. Binding to the spike protein, thereby inhibiting its capability to contaminate host cells23
  2. Inhibiting replication of already contaminated cells
  3. Decreasing contaminated cells’ resistance to therapy with antiviral treatment

Inhibit the SARS-CoV-2 most important protease.24

The Entrance Line Crucial COVID-19 Care Alliance (FLCCC) early therapy protocol25 contains quercetin at a dose of 250 milligrams twice a day, together with 100 mg elemental zinc and 500 mg to 1,000 mg of vitamin C twice a day.

Quercetin in COVID-19 Medical Literature

In Half 3,26 Fashionable Discontent evaluations among the medical trials which have taken place. One COVID-19-specific research27 discovered that individuals who took zinc and two zinc ionophores — quinine drops and quercetin — had decrease incidence of COVID-19 than the management group. Over the course of the research (20 weeks), solely two of the 53 check topics turned symptomatic, in comparison with 12 of the 60 controls. As famous by Fashionable Discontent:28

“Though this didn’t check quercetin in isolation, the research does recommend that over-the-counter, simply accessible compounds could also be extraordinarily helpful in preventing towards COVID, particularly when taken as a prophylactic.”

In one other trial,29 76 outpatients who examined optimistic however had solely gentle signs got 1,000 mg of Quercetin Phytosome® (quercetin in sunflower phospholipids that enhance oral absorption 20-fold) per day for 30 days, along with customary care (analgesics, oral steroids and antibiotics). One other 76 sufferers got customary of care solely.

Within the quercetin group, solely 9.2% of contributors went on to require hospitalization, in comparison with 28.9% of sufferers who acquired customary of care solely. In response to the authors:30

“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 potential anti-fatigue and pro-appetite properties. QP [Quercetin Phytosome®] is a secure agent and together with customary care, when utilized in early stage of viral an infection, may help in enhancing the early signs and assist in stopping the severity of COVID-19 illness.”

Quercetin was additionally featured in two scientific evaluations printed in 2020.31 The primary, printed in within the Integrative Medication journal in Could 2020,32 highlighted quercetin’s promotion of SIRT2, which inhibits NLRP3 inflammasome.

The second assessment article,33 printed within the June 19, 2020, subject of Frontiers in Immunology, highlighted quercetin’s usefulness as a COVID-19 therapy when used together with vitamin C. The vitamin C recycles oxidized quercetin, producing a synergistic impact. It additionally enhances quercetin’s antiviral capability.

Meals as Medication

With the arrival of processed meals, many vital vitamins have been misplaced or minimized within the common particular person’s food regimen. Quercetin, being present in recent fruits, greens and berries is one in every of them. Sadly, whereas important nutritional vitamins and minerals are typically acknowledged for his or her significance, antioxidants akin to quercetin are sometimes missed, and generally labeled as “pseudoscience” or “fad” dietary supplements. As famous by Fashionable Discontent:

“The nice variety of advantages that these compounds contribute to people can’t be overstated … An argument might be made that not solely may quercetin show helpful to our well being, however an absence of it might show detrimental in the long run.”

If COVID-19 has taught us something, it’s the significance of primary well being and a wholesome immune operate. On this regard, a food regimen excessive in recent vegatables and fruits can go a good distance. Dietary dietary supplements even have their place, particularly in conditions like a pandemic.


In conclusion, Fashionable Discontent gives the next abstract of findings:34

“There’s proof that quercetin may match equally to hydroxychloroquine — It appears that evidently quercetin might function as each an immunomodulator and a zinc ionophore. Its use as an over-the-counter anti-allergic complement in addition to its use for bronchial asthma signifies a capability to have an effect on the manufacturing of histamine and cytokines …

Quercetin has loads of different advantages — … Antioxidants … are among the most effectively studied compounds, with potential anti-cancer, pro-heart and pro-organ advantages. Add on potential antimicrobial properties and it turns into onerous to argue that that is nothing greater than a potential fad complement.

Though restricted, there’s some proof that quercetin could also be efficient towards SARS-CoV2 — Pc fashions and in vitro research recommend that ACE2 receptors and the primary protease of SARS-CoV2 could also be good goal candidates for quercetin … the restricted variety of research recommend quercetin could also be efficient, particularly if used early on or as a prophylactic.

Dietary quercetin is the primary supply of quercetin, and its deficiency in trendy diets could also be contributing to our well being issues — Quercetin is primarily sourced from colourful fruits, greens, teas … all meals that lots of our ancestors would have consumed regularly … Fashionable ‘enriched’ meals are inclined to complement with further nutritional vitamins and minerals, however might miss out on different plant-derived compounds which have performed a considerable function in our food regimen.

Much like lowered daylight publicity and the necessity for elevated vitamin D supplementation, we might have to take a look at potential supplementation of missed compounds akin to polyphenols. Sourcing these compounds from actual meals would show essentially the most helpful, however in teams of people that might not have entry to recent vegatables and fruits, quercetin and polyphenol supplementation could also be helpful.

This would come with folks with different diets akin to keto, who might keep away from excessive carb fruits, and thus could also be lacking a key nutrient of their diets.

Quercetin has loads of advantages, and for individuals who could also be lacking out on it of their food regimen they might wish to look into sourcing it with supplementation. Don’t take this as a prescription or advice, however an argument to look at your personal well being and see what it’s possible you’ll be missing …”