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.
(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)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.