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.
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.
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A different computer modeling study, which has not yet been peer-reviewed, also demonstrated that Quercetin showed promise in blocking the SARS-CoV-2 from entering cells.8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.
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:
Please consult your physician first and do not stop taking your blood pressure medications.
Looking beyond the Coronavirus, recent in-vitro and in-vivo animal research suggests that Quercetin supplements could be beneficial in more ways, including:
- Promote brain health – “Mechanisms of Neuroprotection by Quercetin: Counteracting Oxidative Stress and More.” Oxidative medicine and cellular longevity 2016
- Enhance immune function and reduce inflammation – “Quercetin, Inflammation and Immunity.” Nutrients 2016
- Reduce risk of cancer – “Anticancer and apoptosis‑inducing effects of quercetin in vitro and in vivo.” Oncology reports 2017
- Anti-aging – “Restoring Effects of Natural Anti-Oxidant Quercetin on Cellular Senescent Human Dermal Fibroblast.” The American Journal of Chinese Medicine 2018
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.
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.