Coronavirus Episode 9: Can Quercetin Help COVID-19?

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quercetin coronavirus

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 too deep. Yesterday, I came across a research paper that ran simulations about the best drugs or supplements to block the coronavirus from entering cells. In the top 5? Quercetin. So is there anything to this?

What is Quercetin?

Quercetin is a pigment derived from plants that is in the bioflavonoid category (1). It is found in many common plants and foods that we consume, such as onions, berries, red wine, green tea, and apples. In addition, it’s also found in supplements like St. John’s wort, Ginkgo Biloba, American elderberry, and others.

One of the functions of flavonoids such as Quercetin is to act as an antioxidant. That means that it can vanquish free radical molecules believed to be involved in cellular damage as we age. Interestingly, Quercetin is the most common flavonoid in the diet as it’s estimated that the average person eats 10–100 mg of it every day (2). Quercetin is also considered a senolytic, meaning it can both get rid of bad cells and help old cells (3).

The IBM Modelling Study

A study published by the University of Tennessee and Oak Ridge National Labs used the most powerful IBM supercomputer to model which FDA approved compounds or supplements might interfere with the coronavirus binding to cells (4). To review, the coronavirus uses the ACE 2 (Angiotensin Converting Enzyme) receptor to enter cells. Once in a cell, the coronavirus virus empties its RNA contents and hijacks the cell to start producing more viruses. So preventing the coronavirus from binding to the ACE 2 receptor is a good thing as it means the virus can’t get into your cells. The study modeled various compounds and clocking in at number 5 on that list was Quercetin.

Another computer modeling study that has yet to be peer-reviewed also demonstrated that Quercitin and other compounds also showed promise in blocking the SARS-CoV-2 novel coronavirus from entering cells (7).

Is There Other Evidence that Quercetin Works Against Coronaviruses?

First, realize that the novel coronavirus is in a family of coronaviruses that includes everything from other SARS viruses that cause serious respiratory problems to the common cold. As a result, Quercetin has been tested against other viruses in this family. For example, a 2004 lab study showed that it blocked the entry of another SARS coronavirus into cells (5). A 2012 study basically concluded the same thing (6).

Are There Clinical Trials?

A Montreal scientist by the name of Michel Chrétien is studying Quercetin (9). He recently received a 1 million dollar donation to begin a clinical trial. That study was proceeding in China, but now that the virus is controlled there, it may have to move back to Montreal.

However, please realize that the gold standard in medicine is a clinical trial. In this case, one where you give half the patients Quercetin and half a sugar pill to determine if those taking Quercetin end up contracting COVID-19 less often. However, that study has yet to be done here.

Blood Pressure Medications and the Novel Coronavirus

One of the problems recently brought up by experts is that some of the most common blood pressure medications on the market make more of this ACE 2 receptor (called upregulation) (8,10). What’s a receptor? How does upregulation work?

Your cells have receptors on their surfaces. These act as triggers or gateways. For example, a molecule in your blood or plasma can bind to the receptor to flip a switch. These receptors can also act as gateways for the right or wrong things to get into the cell. The ACE receptor we are discussing here is involved in blood pressure control. The coronavirus hijacks this innocent receptor as a way to get into the cell.

What is upregulation? Your body is very good at working around the effects of drugs. For example, if you try to block that ACE 2 receptor, your body will instruct the cells to make more ACE 2 receptors. This is called upregulation.

More ACE 2 receptors may mean that more SARD-CoV-2 viruses can enter cells. Hence, there are concerns that some of the younger people perishing from this disease may be those with metabolic syndrome (overweight, lack of exercise, high triglycerides, and high blood pressure) who have been placed on ACE inhibitors or ARB blood pressure medications.

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

ACE Inhibitors: benazepril (Lotensin, Lotensin Hct), captopril (Capoten), enalapril (Vasotec), fosinopril (Monopril), lisinopril (Prinivil, Zestril),
moexipril (Univasc), perindopril (Aceon), quinapril (Accupril).

ARB (Angiotensin II receptor blockers): azilsartan (Edarbi), candesartan (Atacand), eprosartan (Teveten), irbesartan (Avapro), telmisartan (Micardis), valsartan (Diovan), losartan (Cozaar), and olmesartan (Benicar).

Do not stop taking your blood pressure medications without consulting with your doctor!

How to Take Quercetin

Given that Quercetin is a supplement that has other benefits including possibly antiaging, my sense is that this is one to take right now. The usual dose is 500mg to 1,000 mg a day. It’s also often complexed with other supplements such as Bromelain (a digestive enzyme from Pineapples) or Vitamin C, which are both thought to improve absorption. Hence getting it as a combo with either one is a good idea.

At this point, I do have my family on this supplement. Do I know it works for sure? No, but the circumstantial evidence is good enough for me. However, only you can decide, based on what’s presented and without clinical trials, if the data is compelling enough for you. 

The upshot? Quercetin looks like a reasonable bet at this point. As a result, I visited my local Whole Foods today and picked up some. It’s getting in short supply, as one of my local health food stores was out, but it looks like Amazon intends to restock it again next week and the week after.

_____________________________

References:

(1) 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

(2) 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.

(3) 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

(4) 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

(5) Yi L, et al. Small Molecules Blocking the Entry of Severe Acute Respiratory Syndrome Coronavirus into Host Cells. 

(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

(7) 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

(8) 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.

(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.

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41 thoughts on “Coronavirus Episode 9: Can Quercetin Help COVID-19?

  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

Chris Centeno, MD

Regenexx Founder

Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications.
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