Quercetin – a treatment for coronavirus?

Hey readers. Hope you are well, physically and mentally. Here are some tentative ideas about the link between coronavirus, zinc, and a natural product called quercetin, which is a flavonoid found in food.

You’ve probably heard by now of the drug hydroxychloroquine (HCQ) that has been under investigation for treatment of Coronavirus Disease 2019 (COVID-19). Recommendations from Chinese doctors to employ it (the initial recommendation, on Feb 18 was to employ chloroquine phosphate, a related drug) were followed by a small-scale study from French researchers, published on March 20, which was promising but not definitive. On March 25, a Chinese study reported that HCQ did not have a significant benefit to patients, but the validity of that 30-patient study has since been questioned as it turned out that both the HCQ and control groups were also receiving other antiviral treatments. The majority of patients in that study made good recoveries so it’s hard to say whether HCQ was useful or not, and overall the jury is still out on HCQ.

Let food be thy medicine

An awful lot of the debate over HCQ and other potential treatments for COVID-19 come down to a risk versus reward analysis. When it comes to health, I usually tend to follow Hippocrates’ advice: “Let food be thy medicine,” because eating a healthy diet offers a reward at virtually no risk. How big a reward would it offer in the face of COVID-19? Well, there has been a barrage of articles warning against coronavirus-related fads (such as drinking tonic water because it contains quinine) but most people agree that the best defenses against the virus (besides limiting its spread) are exercise, sleep, and a healthy diet. A NY Times article on March 23  warned against an over-zealous use of supplements but concluded that it’s important to get nutrients such as zinc from a healthy diet of whole foods. Two days later, an article on CNN highlighted foods that provide good sources of immunity-boosting nutrients such as vitamin C and zinc. But to be frank, this is all fairly lightweight reporting and there hasn’t been enough focus on the importance of a healthy diet.

The importance of zinc

Since 2010, we have known that zinc inhibits replication of coronavirus in vitro – it was tested on SARS-CoV, which was responsible for the SARS outbreak in 2002. Zinc has long been recognized as an important component of our viral defenses and we should make sure to get enough of it in our diets. As the above-mentioned NY Times article pointed out, you can sometimes do damage if you overdo it on nutritional supplements – your body can only absorb so much zinc – so if you do supplement, stay within the recommended range of around 10 mg per day. Many more people than previously thought are actually zinc-deficient; A 2017 review on zinc, summarized that nearly 30% of the elderly population is zinc-deficient and that:

“In developing countries, zinc deficiency is the 5th leading cause for the loss of healthy life years. In industrial countries, mainly the elderly population is affected by zinc deficiency.” 

Personally, I’ll be relying mainly on food sources for my zinc supply, such as seeds, legumes, mushrooms and spinach. But there’s one other important factor besides getting zinc into our bodies and that’s getting it into the cells that are threatened by coronavirus.

Hydroxychloroquine is a zinc ionophore

In the 2010 study that looked at inhibition of coronavirus replication by zinc, the researchers found that zinc ionophores block replication of the virus when administered to cell cultures. Ionophores are chemicals that can help transport ions, such as zinc, across cell membranes (because metals like zinc can’t move freely in and out of cells). Now, it turns out that in 2014 it was discovered that HCQ is a zinc ionophore, i.e., it can deliver zinc across cell membranes. On March 10, Dr. Roger Seheult, reporting for MedCram, looked at a hypothesis that the mode of action of hydroxychloroquine could be by delivering zinc to our cells. Here’s that video, which references the papers mentioned above.

Now, it must be pointed out that this is all pretty hypothetical. The facts are that zinc was shown in vitro to inhibit coronavirus replication and that HCQ is a zinc ionophore. But it’s still uncertain that HCQ will be effective against coronavirus and even if it is, the mechanism may not even be zinc-related. Medicine is complex and a drug can have many different impacts on the body. The authors of the 2014 paper that established that HCQ can act as a zinc ionophore point out that:

“Chloroquine exerts a pleiotropic effect in eukaryotic cells, including an elevation of vacuolar pH when trapped in acidic organelles, such as lysosomes.”

Raising the pH of lysosomes is one of the main hypotheses for the mechanism of action of HCQ. The action of raising the pH may be somewhat related to HCQs property as an ionophore as they both involve the movement of ions across membranes.

In the next video, following up on the theory that the mechanism of HCQ could be zinc-related, Dr. Seheult raises the question: Are there other zinc ionophores that could work?

And that’s where quercetin comes in.

Chemical structures of the drug hydroxychloroquine and the natural product quercetin
Two zinc ionophores: the synthetic antimalarial drug, hydroxychloroquine (left) and the naturally occurring flavonoid, quercetin.

Quercetin – a naturally occurring zinc ionophore.

Quercetin is a flavonoid (a type of polyphenol) that’s present in a variety of edible plants – from herbs like cilantro and dill, to veggies and fruit such as onion, kale and cranberries, with the highest concentration found in capers. Quercetin was demonstrated to be a zinc ionophore in 2014.

“Dietary plant polyphenols such as the flavonoids quercetin (QCT) and epigallocatechin-gallate act as antioxidants and as signaling molecules. Remarkably, the activities of numerous enzymes that are targeted by polyphenols are dependent on zinc. We have previously shown that these polyphenols chelate zinc cations and hypothesized that these flavonoids might be also acting as zinc ionophores, transporting zinc cations through the plasma membrane.”

If HCQ proves to be effective in treating COVID-19 then it’s possible that quercetin in our diet may also be protective (while avoiding the side effects of HCQ). But that’s also predicated on quercetin having a similar effect to HCQ in patients and again, medicine is complex.

Quercetin – other chances that it may be helpful in treating COVID-19

Quercetin and plants that contain it have a certain following for treatment of various conditions – for example, capers are used in Iranian Traditional Medicine. Taking a look at the scientific studies carried out specifically on quercetin, here are some highlights:

  • In 2015 it was reported that quercetin inhibits entry of the influenza A and the H5N1 virus to cells in vitro.
  • Quercetin was also found to inhibit adhesion of the human respiratory syncytial virus (hRSV).
  • Researchers from Oak Ridge National Lab used the world’s most powerful supercomputer, SUMMIT, to look for small molecules that might inhibit the COVID-19 spike protein from interacting with human cells and interestingly, quercetin is fifth on that list.
  • This is not a peer-reviewed scientific publication but Leo Galland also recommends quercetin, but via a different mechanism (mTOR modulation). Incidentally, his other recommendations can also be obtained from food sources: curcumin (turmeric), rosmarinic acid (rosemary, sage, oregano), resveratrol (red wine and grapes), and elderberry.

So it boils down to two possible benefits from quercetin: modulation of zinc transport into cells (and possibly altering the pH in lysosomes) and blocking viral docking to host cells.

Bottom line: should you eat quercetin-rich foods?

I feel comfortable with the idea of eating zinc-rich foods that also qualify as healthy foods (e.g., seeds, legumes, mushrooms, and spinach). I’m somewhat comfortable with doing the same for foods that are moderately rich in quercetin (e.g., kale, onions, peppers, and elderberry juice). The one thing that gives me pause is that consumption of the most quercetin-rich food, capers, is high in the countries where COVID-19 has a strong mortality rate: Italy, Spain, France and Iran. I know – there are myriad reasons why these countries are more strongly impacted. I also know that some of the above is merely armchair science. But I figure that it’s useful to share thoughts in case they spark an idea or study that can take us a little closer to a treatment.

For more reading on a range of health topics, check out the category on ethical consumerism and health.

24 thoughts on “Quercetin – a treatment for coronavirus?

  1. Great information. I’m a believer in food as medicine and eat a plant based diet which includes the ones you mentioned. Thank you for passing this along. It all makes sense to me.

    1. https://www.sciencedirect.com/science/article/pii/S1021949814001379
      Temperature-dependent studies on the total phenolics, flavonoids, antioxidant activities, and sugar content in six onion varieties
      …..Quercetin and its glucoside contents increased up to 120°C and then decreased at 150°C, whereas the sugar content continuously decreased with heating. All cultivars showed the same pattern in the heating effect, and the predominant flavonoids were destroyed at higher temperatures. Therefore, it is improper to expose onion powder to a temperature higher than 120°C.

  2. Great piece! I’ve got my kale and peppers and onions and spinach and mushrooms and elderberry (does elderberry gin count ROFL!) coupled with being an introvert, so I think I’m good, right? ahahaha (

      1. Not bad thanks! Trying to adopt new habits (which will be the subject of my next post!) and make the best of the time.
        How about you?

      2. Exactly the same here! LOL Been redoing my…I don’t even know what to call it?…schedule? Mission statement? Business plan? Strategizing?…for the next few months. Lockdown (not that anyone is paying attention to it) has been extended to April 30.

  3. capers is a food that you eat A LITTLE BIT at a time
    so you can not say that people in Italy, France and Spain and Iran eat a lot of capers
    i have not seen an Iranian/italian / french /spanish dish with a lot of caper in it
    Furthermore, don’t forget that Quercetin has very low absortion

    1. Well I mean that people in these countries eat more capers than average.
      But I take your point that that’s still not a large volume of capers, and while capers are significantly higher in quercetin than other foods, absolute intake may not be that significant compared to, say, onions and kale. Solubility of quercetin in water is very low, but intake with food would aid with absorption. Thanks for commenting!

  4. I was trying to find out if Quercetin and Quinine is the same thing. Your article is leading me to say yes it is. I can’t find any information until I came across your. What’s your thoughts? Thank you!

    1. Hi Michele!
      No, they are very different. Quinine isn’t the same as hydroxychloroquine (HCQ) either and although quinine used to be used for protection against malaria, there are no studies that I know of on the use of quinine to treat coronavirus. Even the evidence that HCQ is protective is looking less certain as new research comes out. Hope this helps!

  5. You do realize that HCQ has kept the death count low in South Korea? Quite a number of American doctors have had remarkable success using it. Dr. Zelenko has treated more than 1,000 people very successfully. Another Doc, I believe he is in Colorado, says that he has had 100% success using HCQ. I assume they all use Z-pak and Zinc, as well. Only in America could we see such clinical success and still say that the trials are not looking good. Science in the US is so corrupt, so driven by profit and elite agendas, that I don’t care for a moment what the “clinical trials” show. They want to push vaccines. They want to kill the economy in the hopes of bringing in a Democrat president in November. They couldn’t care less if millions die of starvation and end up with no livelihood. We are surrounded by criminals in this country today, unfortunately. I am far more interested in what is working than in what many “experts” (Fauci, for example) have to say.

    1. I was looking at querctin and noticed your post. You have called it perfectly!
      Fauci and his co-conspirators have done a decent job of hiding HCQ from the public. BUT unfortunately for them, millions in the public now know that HCQ+Zn is a home run, almost a 100% cure for COVID-19.

      Last month I was given in house symptoms that fit. When I lost taste/smell, I was convinced. I had to drive 2 hours to see Dr that UNDERSTOOD the Zelenko Protocol. BOTH of us showed quick improvement. My chest congestion got better next day, and 2 days later, my smell and taste returned! SO in our test of TWO, it was 100%. One of the possibilities of who infected this house died on Wednesday. I have told family members/friends that they need to get HCQ by a telemed Dr. as I was in Mexico yesterday and the border agents HAVE FDA DIRECTIONS that no HCQ comes in w/o a valid prescription AND the limit is 50 pills.

      The agent says HCQ is being misused, I corrected him to say the FDA is intentionally killing people to hide the fact that it is effective in saving lives. I know of THREE ways to get HCQ but I only mentioned the one online MD source.

  6. Apparently, my comment didn’t post. I will try again. HCQ is being used with remarkable success in the US and around the world. I couldn’t care less about their so-called trials. Our medical/scientific community is almost as corrupt today as Washington DC. We can see very clearly that HCQ works. Why should we listen to “scientists” who are government or Pharma influenced? The ruling class wants a vaccine. They are not interested in any simple, inexpensive common treatment, such as HCQ. There is no way this treatment is going to receive broad approval or recognition inside the US.

  7. I don’t know of what this article speaks..I can testify that I have had fever blisters for over 45 years and started Quercetin January and haven’t had one since.
    If I feel the itch/burn sensation, I take 3 tablets morning, afternoon, and bedtime and no fever surfaces.

  8. Be careful when taking zinc. It opposes copper in the body and copper is needed for healthy nerves, blood vessels, skin and hair and a healthy immune system. The body cannot make healthy mast cells without it. Always use all minerals in balance with the minerals the body needs that oppose them. The Linus Pauling Institute ratio is not correct. It’s too heavy on zinc.

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