Can Quercetin Help Fight The Coronavirus?

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About a week ago, a longtime patient sent me an email about the supplement Quercetin. I thought it was interesting, but I didn’t look further into it.

Yesterday, I came across a research paper that ran simulations about the best drugs or supplements to block the coronavirus from entering cells1. Quercetin was in the top five. Let’s look and see if there is anything to this.

potential benefits of quercetin listed over an image of pills

What is quercetin?

Quercetin is a naturally occurring plant pigment (bioflavonoid2) present in colorful fruits and vegetables like onions, berries, red wine, green tea, and apples. It’s commonly used in medicine, supplements, and even skincare due to its antioxidant properties — its ability to fight cell-damaging free radical molecules3. Plus, it is also a senolytic and can help fend against cellular senescence4, which contributes to aging and aging-related diseases.

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What’s the research on quercetin and the Coronavirus?

The term Coronavirus refers to the family of viruses that includes everything, from other SARS (Severe Acute Respiratory Syndrome) viruses that cause serious respiratory problems to the common cold. Quercetin has been tested for some Coronaviruses but not specifically for the novel Coronavirus, also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus that causes COVID-19.

Coronaviruses use ACE 2 receptors to enter cells, and once inside, it hijacks the cell and starts producing more viruses. According to the research, Quercetin might interfere with the coronavirus entering and binding to cells.5, 6

A 2020 study published by the University of Tennessee and Oak Ridge National Labs used the most powerful IBM supercomputer to model how compounds or supplements, approved by The U.S. Food and Drug Administration (FDA), might interfere with the coronavirus binding to cells. Quercetin was number five7.

A different computer modeling study, which has not yet been peer-reviewed, also demonstrated that Quercetin showed promise in blocking the SARS-CoV-2 from entering cells.8

Although there have not been any clinical trials yet, that will change soon. Canadian scientist Michel Chrétien, who is one of the world’s most cited scientists, has received a 1 million dollars donation to begin a clinical trial9. We will all be watching.

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Quercetin, Coronavirus, and blood pressure medication

New studies by The International Society of Travel Medicine and The Lancet Respiratory Medicine have raised concerns about a possible side effect of blood pressure medication10, 11. Younger people dying of COVID-19 might be those with metabolic syndrome (overweight, lack of exercise, high triglycerides, and high blood pressure) prescribed ACE inhibitors or ARB blood pressure medications.

Some of the most common blood pressure medications make the body produce more ACE 2 receptors. These are the receptors that the Coronavirus binds onto to enter the cells, which could mean more SARD-CoV-2 viruses can enter cells.

What are those blood pressure medications? Here’s a complete list:

List of the most common blood pressure medication

Please consult your physician first and do not stop taking your blood pressure medications.

Final thoughts

Looking beyond the Coronavirus, recent in-vitro and in-vivo animal research suggests that Quercetin supplements could be beneficial in more ways, including:

Quercetin looks like a reasonable bet at this point.

Do I know it works for sure? No, but the circumstantial evidence is good enough for me, and it is a supplement my family takes. However, only you can decide if the data is compelling enough for you.

If you decide to try a Quercetin dietary supplement, I’d suggest getting one with Vitamin C or Bromelain, as both are thought to improve absorption.

————
References:

1, 7. Smith, Micholas; Smith, Jeremy C. (2020): Repurposing Therapeutics for COVID-19: Supercomputer-Based Docking to the SARS-CoV-2 Viral Spike Protein and Viral Spike Protein-Human ACE2 Interface. ChemRxiv. Preprint. https://doi.org/10.26434/chemrxiv.11871402.v3

2. Anand David AV, Arulmoli R, Parasuraman S. Overviews of Biological Importance of Quercetin: A Bioactive Flavonoid. Pharmacogn Rev. 2016;10(20):84–89. doi:10.4103/0973-7847.194044

3. Bischoff SC. Quercetin: potentials in the prevention and therapy of disease. Curr Opin Clin Nutr Metab Care. 2008 Nov;11(6):733-40. doi: 10.1097/MCO.0b013e32831394b8.

4. Malavolta M1, Pierpaoli E, Giacconi R, Costarelli L, Piacenza F, Basso A, Cardelli M, Provinciali M. Pleiotropic Effects of Tocotrienols and Quercetin on Cellular Senescence: Introducing the Perspective of Senolytic Effects of Phytochemicals. Curr Drug Targets. 2016;17(4):447-59. https://www.ncbi.nlm.nih.gov/pubmed/26343116

5. Yi L, et al. Small Molecules Blocking the Entry of Severe Acute Respiratory Syndrome Coronavirus into Host Cells. Journal of Virology Sep 2004, 78 (20) 11334-11339; DOI: 10.1128/JVI.78.20.11334-11339.2004

6. Nguyen TTH, Woo HJ, Kang HK, Nguyen VD, Kim YM, Kim DW. et al. Flavonoid-mediated inhibition of SARS coronavirus 3C-like protease expressed in Pichia pastoris. Biotechnol Lett. 2012;34:831-8 https://www.ncbi.nlm.nih.gov/pubmed/22350287

8. Khaerunnisa S, et al. Potential Inhibitor of COVID-19 Main Protease (Mpro) from Several Medicinal Plant Compounds by Molecular Docking Study. Preprints (www.preprints.org). https://doi.org/10.20944/preprints202003.0226.v1

9. MacClean’s. A made-in-Canada solution to the coronavirus outbreak? https://www.macleans.ca/news/canada/a-made-in-canada- solution-to-the-coronavirus-outbreak/ Accessed 3/19/20.

10. Diaz JH. Hypothesis: angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may increase the risk of severe COVID-19. J Travel Med. 2020 Mar 18. pii: taaa041. doi: 10.1093/jtm/taaa041.

11. Fang L, Karakiulakis G, Roth M. Are patients with hypertension and diabetes mellitus at increased risk for COVID- 19 infection? Lancet Respir Med. 2020 Mar 11. pii: S2213-2600(20)30116-8. doi: 10.1016/S2213-2600(20)30116-8.

Category: Coronavirus

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58 thoughts on “Can Quercetin Help Fight The Coronavirus?

  1. Peter

    Thank you Dr Centeno. If already prescribed Losartin would adding Quercetin decrease the efficacy of Losartin?

    1. Chris Centeno, MD Post author

      Unknown, but unlikley

  2. Ariel

    Can you also discuss chloroquine and if it’s effective to covid19…

    Thanks

    1. Chris Centeno, MD Post author

      Will do…

  3. Kay

    Our family pairs this with our flu vaccine every year from beginning to end of flu season because years ago we saw the research that showed almost no flu in those who combined this with flu vaccine. Even in the years the flu vaccine yielded sub optimal results, we never had the flu despite taking care of those who did get sick nor did the people in the study. Scientific? No. But we are going to keep letting the results speak for itself. The studies were done with elderberry plus flu vaccine. We use 500 mg. and add quercetin rich foods during the flu season to smoothies which taste wonderful like elderberries and dried apple PEEL (a really rich source of quercetin and plentiful in our area). This year we plan to keep taking this. Can’t hurt. We do eat lots of onions in the winter. Not sure I’d want them in my smoothie. lol. Such a great post.

  4. Heidi

    Cream of Tartar is high in Quercetin, but couldn’t find exact amount. But black soy beans has 2000mg per cup! – just in case you can’t find the powder and before people find out about cream of tartar…

  5. Morgan

    Thanks for the info! Could you please provide a link to the article. What are the top 4?
    Thanks

    1. Chris Centeno, MD Post author

      The link to the article is in the references.

  6. Jeremy

    I read the results of a 2016 Ph1 dose escalation trial that involved chronic hepatitis patients. The investigators never hit the MTD even though they dosed up to 5g for 28 days. With efficacy determination not being a primary goal of Ph1 trials, it was interesting to see that 8 patients showed clinically meaningful decreases in viral load. Based on this trial and other references about quercetin’s potential to treat Covid-19, I purchased 250g earlier this week. My plan is to reserve the supplement until I or a family member starts showing symptoms. Given the safety profile, I would likely dose at 5g for myself and a bit less for my wife and teenagers. It would be great to see the results of the trial that started in China soon but I will take the supplement if needed regardless.

    1. Chris Centeno, MD Post author

      My guess is that this is a good idea as a daily preventative, not necessarily a treatment for the disease. Remember that viruses work by first binding to cells and then entering and commandeering the cell to make more viruses. Hence, the fewer cells that the virus can successfully bind to, the better chance your immune system has to stay on top of the situation before it spins out of control

  7. Matt

    Yes, take as a preventative and multiple times a day, the current clinical trial will be dosing 4 times a day but 3 times a day is likely enough as the half life is rather short, sadly have not been able to find exact dosages in the study, also the bioavailability of Quercetin is poor but the Bromelain and vitamin c have been shown to enhance absorption.

  8. Rachel

    “Possibly, a lab study that has yet to be peer-reviewed demonstrated that Quercitin and other compounds showed promise in blocking the SARS-CoV-2 novel coronavirus from entering cells (7).” This is incorrect. This was a study using a software program on a computer. To date, quercetin has not been tested against SARS-CoV-2 in any laboratory setting.

    1. Chris Centeno, MD Post author

      Rachel, thanks for pointing that out, changes were made to the blog to reflect that fact.

  9. Alex Tworkowski

    In the top 5? Quercetin. What were the others?

    1. Chris Centeno, MD Post author

      See the paper at the citation link.

  10. Deb

    I have been taking high dose quercetin twice a day as suggested by my naturopath since November to help with RA. Hoping this does work. My husband is on a Ace Inhibitor could Quercetin help block receptors?

    1. Chris Centeno, MD Post author

      Your husband should talk to his doctor about getting off the ACE inhibitor for now.

  11. William

    Could my Dr. Switch me to a better blood pressure med for the time of the Covid 19 outbreak ? Lisinopril is what I am on now. Thank you

    1. Chris Centeno, MD Post author

      That’s something you need to speak with your physician about.

  12. Corey

    I’ve been on Losartan, amlodipine and chlorthalidone. I asked my Dr. about changing this and he said he has seen some research that ARBs may be beneficial. What is your opinion on this and would Quercetin interfere with any of these meds?
    Thank you!

    1. Chris Centeno, MD Post author

      I know of no research that ARBs are beneficial, show you doctor this article: https://www.sciencedaily.com/releases/2020/03/200323101354.htm

  13. Tom

    Thanks for the post Chris! I bought quercetin in a panic when I seen the article from Quebec . We’ve been experiencing some symptoms of the virus ( coughing and possible shortness of breath. Although that I may have been anxiety induced ). Our stomachs started turning yesterday and I’m thinking something is definitely up. I want to take quercetin my only hesitation is we can’t see any results of the study yet, or can we ? Ive also got an autoimmune deficiency called ankylosing spondylitis.

    1. Chris Centeno, MD Post author

      No info yet, but you should definitely see a physician.

  14. Lynn

    I read a study that stated Quercetin lowered blood pressure and acted similar to an ACE inhibitor. Can you share insight on this? I know ACE inhibitors cause an upregulation of ACE2 receptors, making it easier for COVID-19 to bind (in theory) but how would quercetin cause lowering of BP,? This is my only hesitation on taking quercetin. Thank you for your time. Reference:
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991028/ specifically section 4.2

    1. Chris Centeno, MD Post author

      That study posits many possible mechanisms for how quercetin may reduce blood pressure and doesn’t settle on any one mechanism.

  15. Rosalie Malkiel

    I am 81 years old, not on any medication, thank God. I take supplements of which 2,000 units of Vitamin C is part of this. Do I still need quercitin? By, the way I recommended quercitin to my relative for her asthma.

    1. Chris Centeno, MD Post author

      Those are questions for your doctor.

    2. Chris Centeno, MD Post author

      This is something you need to speak to your doctor about…

  16. Cindy Bartman

    Why doesn’t Quercetin cause the same upregulation that the ARBs cause? It seems they have the same mechanism of action.

    1. Chris Centeno, MD Post author

      I would think that would be unlikely given that it doesn’t specifically block ACE2 receptors.

    2. Chris Centeno, MD Post author

      See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991028/, lots of proposed mechanisms for why Quercetin works for blood pressure.

  17. Cynthia Bartman

    Does quercetin increase the upregulation of ACE 2 receptors?

    1. Chris Centeno, MD Post author

      I would think that would be unlikely given that it doesn’t specifically block ACE2 receptors.

    2. Chris Centeno, MD Post author

      That’s unknown at this time.

  18. Fred Lander

    Quercetin has enormous advantages over the TNF-α suppressors , in that it will not lower the cytokine more if it is already in the normal range ( two studies showed that ) and if it very high the quercetin will lower it proportionally:
    https://www.clinicalnutritionjournal.com/article/S0261-5614(11)00026-4/fulltext

    Very nice plain language presentation Dr. Centeno

  19. Max

    I’m amazed at how little discussion there is of the flavones/flavonoids as a possible treatment for the various SARS viruses, especially with the current pandemic. In addition to Quercetin, Naringenin has also been studied, along with catechin, sylmarin and others for their positive effects on viral replication and uptake, specifically with regard to HCV. I suspect we would see more of this if these compounds weren’t so easily obtained via supplements and balanced diets, as opposed to expensive antiviral pharmaceuticals.

  20. Maggie Oneil

    I was able to get Quercetin in powder form for an affordable price. Could I just take it along with a separate vitamin c pill? I found a much more expensive Quercetin that has bromelain with it. Looking for lowest cost option.

    1. Chris Centeno, MD Post author

      Likely that would be fine.

  21. Fhre

    Candied Citrus peel has a huge amount of Quercetin. My depression era grandparents on both sides of my family always had this for us kids, growing up. The all survived the 1918 flu and lived into their 90s. Lucky for me, it is orange and Lemon season here! Flavonoid derivatives, expressed in quercetin equivalents, in Mauritian citrus flavedos were generally high (>2000 μg/g FW for the majority of samples analysed) https://www.sciencedirect.com/science/article/pii/S1658077X16300960

  22. Dominique Godin

    Great article. I start taking this week Quercetin the one I found is from Natural factors is a bioactive Quercetin EMIQ ( Enzymatically Modified Isoquercitin) that is said that have 40 times more absorption than standard quercetin. My Quercetin is only 50mg which should be equivalent to a high dose from the standard form. My question: Is that higher absorption in 50mg is valuable in the case of COVID-19 or I should take standard one at 500 to 1000mg a day?

    Thanks

    1. Chris Centeno, MD Post author

      Unsure

  23. Edward Haines

    I live somewhere that outside US that is difficult to find Querceti. I managed to find a small amount. Is there an advantage to keeping this aside should I become ill? I’d rather have it available in that even than take as a prophylaxis.

    What do you think?

    1. Chris Centeno, MD Post author

      Unsure if it will help if you’re ill.

  24. Paul King

    Three weeks ago, at the urging of a close doctor friend who is a FRSC, I began taking Quercetin Complex containing Vitamin C additive (250 mg 2x daily). My decision was reinforced upon reading about Dr. Michel Chretien’s past non-clinical findings with other deadly viruses and his intention to do clinical trials with Quercetin. I was also urged to take zinc tablets but have refrained. Can you comment on the zinc? Secondly, can you confirm sources that Chretien obtained the funding needed and that clinical trials have actually begun in China or have been transferred to Canada?

    1. Chris Centeno, MD Post author

      I wasn’t able to confirm that this trial is up and running.

  25. John

    Thank you for posting this.

    One thing i found notably absent though is the fact that quercetin, like hydroxychloroquine, acts as a zinc ionophore and increases intercellular zinc levels. Zinc has been established as having direct antiviral and immune regulating properties and zinc deficiencies are notably associated with old age and almost every other high risk comorbidity associated with Covid-19, including the use of some ACE inhibitors. In the last couple of weeks I have seen several people, notably Dr Cardillo based out of LA, suggesting that hydroxychloroquine is more effective when used early on in conjunction with zinc, suggesting the zinc ionophore activity is a key mechanism of action inhibiting viral replication in vivo. This would reinforce the notion that quercetin could be an effective prophylactic or treatment, specifically used in combination with zinc supplements.

    I would be interested in your thoughts on this.

    1. Chris Centeno, MD Post author

      I’ll have to do a post on Zinc at some point so I can review the literature out there on SARS-Cov-2

  26. Gary

    When I worked in medical research 35 years ago, my group studied the group of compounds known as flavonoids, starting with quercetin. In vitro it had potent anti cancer, antihistamine and anti viral effects. We were not set up to perform in vivo studies. It would be truly amazing if quercetin or a similar flavonoid could be used in the fight against the coronavirus.

  27. Janet SWeinglass, Ph,D

    Quercetin I(like Curcumin) is A powerful both with low bioavailability which makes it very hard to get enlugh from foods or supplements. Has anhyone found a solution

    1. Chris Centeno, MD Post author

      Bromelain helps Quercetin like Bioperine helps curcumin.

  28. john flynn jr.

    Fisetin is another very interesting flavonoid close to Quercetin in antiviral activity.
    Whereas, its being researched by the Mayo Clinic … (Senescent cell research moves into human trials) pulmonary fibrosis
    However, it has also shown some antiviral activity

    1. Chris Centeno, MD Post author

      Yes, I take it every morning!

  29. Yonit Gefen

    Difficulties in using Quercetin relate to is low bioavailability. Does anybody have information on substances (as in pepper sand oil with curcumin) that increase bioavailability? Have there been any instances where quercitin is given IV?

    1. Chris Centeno, MD Post author

      Check out Bromelain.

  30. jamal

    hi
    i came across youre blog and i wanted to respond to it.
    I came across the quercetine and never paid attention to it. Recently i became ill and still not tested for the covid19 due to shortage of testing material in the netherlands ( europe ) The doctor of mine doesnt no anything to do with me. I started having strange symptoms including respiratory problems.

    i know i have problems with an infection i was dealing with in my prostate for some time now also i know i have a colon problem IBS.

    I started limping and sometimes me left leg stops with functionality. also on the left side. I know my bloodflow is not so good and this problem concentrates and manifests on the left side of my body.

    No suddenly almost 2 months ago i started getting mild covid symptoms and i went to the doctor after she gave me antibiotics and my health got worse. I quickly stoped the antibiotics because i almost got to the hospital due to respirator problems. But yet still i was struggling.

    I started supplementing by taking garlic on an empty stomach and started fasting to let my body heal and my bowel to start moving again. after some days i noticed that it got better by maybe 5% or 10 %.

    Then i started taking the Quercetine together with the garlic.
    * so garlic at night ( 2 Cloves crushed )
    * Quercetine 250MG and Vit C 750 MG
    * Zinc 15MG ( this i started to give the immunity a boost ) Quercitine started to work before the zinc….

    Then suddenly the leg was restoring
    The pain and burning sensation left chest side was dissapiring
    Pain left side back / started getting less.

    I have planned this week in the hospital to test my blood if its containing the covid so we know for sure if i had it..

    So the Quercitine is deffently doing things in the body with the blood flow and virus problems and also respiratory problems. But i think also that it depends on some factors of the person and his health conditions and in what way it works for that person. I believe that if you have a bloodvessel or bloodflow issues and you catch the flu / virus you will get a harder reaction.

  31. Russ Delaney

    I take a lot of supplements. There is so much more that goes into being healthy of course and I try to do as much as possible of the good things and as few of the bad things as I can. Even before the Covid-19 started I had been taking a lot of Quercetin along with Bromelain, 2000 mg/Quercetin and 1000mg Bromelain split into two doses daily, so I was glad to hear about Quercetin’s potential role in helping people with Covid-19. I started out with a smaller dose and worked my way up. My regular routine also includes fat and water soluble Vit C up to bowel tolerance, and 6000iu of Vit D3, which I get checked once a year. I’m 66 now. I’ll let you now how this works out for me. I would imagine there’s not too many people out there doing this. I keep telling myself to cut back. These things do cost money. I have a system of taking supplements so I do it consistently, so it’s as though I’m doing a study on myself. I have records. If I live to 115 and they ask me how I did it I guess I will have some documentation.

  32. Mary

    My husband, myself, our son & his wife all began taking quercetin in mid-March–500 mg/day. Both my husband & son are now experiencing knee pain & swelling, which started about 2-3 weeks ago. Neither of them can recall any injury preceding this. I did an internet search & found a site which listed fluid accumulation in the knee as one of the possible side effects of quercetin (https://www.drugs.com/sfx/quercetin-side-effects.html). Has anyone else experienced this? Will it go away after quercetin is discontinued?

    1. Chris Centeno, MD Post author

      If you believe this is caused by the Quercetin, then it would be a good idea to stop taking that supplement.

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