Can Quercetin, Vitamin C, Vitamin D and Zinc help Against Coronavirus?

As the outbreak of novel coronavirus, COVID-19 continues to spread around the world, researchers are feverishly searching for effective remedies. As of March 31, 2020, there were 143 clinical trials of COVID-19 treatments or vaccines that are either ongoing or recruiting patients. New ones are being added every day. The drugs or treatments being tested range from repurposed flu treatments and stem cell therapy to malaria treatments (chloroquine and hydroxychloroquine) that were first developed decades ago.

However, do take note that most of these therapies under evaluation are mainly hospital-based treatments. These are not something that you take normally as a preventive strategy. For example, QT prolongation (causing irregular heart beats), hypoglycaemia, eye toxicity are some of the risks to be mindful of from drugs like hydroxychloroquine and azithromycin.

Do not self-medicate with prescription drugs. A couple in Arizona mistakenly thought that a popular fish tank additive that has chloroquine was safe to ingest. It was not and this stuff ended up killing him with his wife in the ICU. Hence, please be careful out there!

Research has shown that supplementing with certain vitamins, minerals and other substances can improve immune response and potentially protect against illness. Do I know it works for COVID-19? No. Only you can decide, based on what’s presented and without large clinical trials, if the data is compelling enough for you.

Note that some supplements can interact with prescription or over-the-counter medications you’re taking. Some may not be appropriate for people with certain health conditions. If you are on medications, be sure to talk with your doctor before starting any supplements.

This guide can help you make sense of the options and to separate the facts from fiction.

1. Vitamin C

Most people turn to vitamin C after they've caught a cold. Because your body doesn't produce or store it, you need daily vitamin C for continued health. Almost all citrus fruits are high in vitamin C.

Vitamin C appears to be able to both prevent and treat respiratory and systemic infections by enhancing various immune cell functions. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100–200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased metabolic demand. (PubMed).

A large review of 29 studies in 11,306 people demonstrated that regularly supplementing with vitamin C at an average dose of 1–2 grams per day reduced the duration of colds by 8% in adults and 14% in children (PubMed).

Interestingly, the review also demonstrated that regularly taking vitamin C supplements reduced common cold occurrence in individuals under high physical stress, including marathon runners and soldiers, by up to 50% (PubMedPubMed).

Additionally, high dose intravenous vitamin C treatment has been shown to significantly improve symptoms in people with severe infections, including sepsis and acute respiratory distress syndrome (ARDS) resulting from viral infections (PubMedPubMed).

However, note that taking large doses of vitamin C (ascorbic acid) on a regular basis lowers your level of copper, so if you are already deficient in copper and take high doses of vitamin C, you can compromise your immune system.

On Feb 11, 2020, a study on "Vitamin C Infusion for the Treatment of Severe 2019-nCoV Infected Pneumonia” was posted to by Chinese researchers.

As of Mar 28, 2020, there were 2 new studies related to Vitamin C for COVID-19 on One in Italy and the other in Saudi Arabia.

On the Chinese Clinical Trial Registry, there is another new trial registered on Vitamin C and COVID-19: A randomized, open, controlled trial for diammonium glycyrrhizinate enteric-coated capsules combined with vitamin C tablets in the treatment of common novel coronavirus pneumonia (COVID-19).

Time will tell what the outcome will be.

2. Vitamin D

In a 2019 review of randomized control studies in 11,321 people from 14 countries, supplementing with vitamin D significantly decreased the risk of respiratory infections in people deficient in this vitamin and lowered infection risk in those with adequate vitamin D levels (PubMed).

Other studies note that vitamin D supplements may improve response to antiviral treatments in people with certain infections, including hepatitis C and HIV (PubMedPubMedPubMed).

A study that was published in the Journal of the American Geriatrics Society in 2016, revealed that
elderly patients who had high doses of the Vitamin D3 were 40 per cent less likely to develop lung infections. Pneumonia, bronchitis and influenza are known to have higher death rates among older people because of their weakened immune system. Experts believe vitamin D helps to reinforce the first line of defense as people age, to prevent acute respiratory infections.

As for the dosage, anywhere between 1,000 and 4,000 IU of supplemental vitamin D per day is sufficient for most people, though those with more serious deficiencies often require much higher doses (PubMed).

3. Zinc

Numerous studies reveal that zinc supplements may protect against respiratory tract infections like the common cold (PubMedPubMed).

What’s more, supplementing with zinc may be beneficial for those who are already sick.

In a 2019 study in 64 hospitalized children with acute lower respiratory tract infections (ALRTIs), taking 30 mg of zinc per day decreased the total duration of infection and the duration of the hospital stay by an average of 2 days, compared with a placebo group (PubMed).

Supplemental zinc may also help reduce the duration of the common cold (PubMed).

Taking zinc long term is typically safe for healthy adults, as long as the daily dose is under the set upper limit of 40 mg of elemental zinc (PubMed).

Excessive doses may interfere with copper absorption, which could compromise your immune system.

4. Quercetin

study published in 2020 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. 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 at number 5 on the list as those that has the potential to block the virus was Quercetin.

2004 study showed that Quercetin blocked the entry of another SARS coronavirus into cells. A 2012 study basically concluded the same thing (PubMed). This coronavirus is called SARS-CoV-2 and is different from the others in its family. So has Quercetin been shown to do anything that prevents this novel virus from entering cells? A lab study in 2020 that has yet to be peer-reviewed, demonstrated that Quercetin and other compounds showed promise in blocking the SARS-CoV-2 novel coronavirus from entering cells.

Wrapping It up

Please take note that the dosages for micronutrients are higher for treatment as opposed to maintenance. This is probably due to higher demand or the deficiency of the micronutrients are worse during a complicated viral infection. However, for prevention or maintenance, the dosages for most of the micronutrients are much lower.

Aside from supplements, there are other ways that may help improve immune response and to prevent you from catching the coronavirus.
  • Wear protective mask. This is an important public health method to curb the spread. It's not just about protecting yourself but will also protect others from you.
  • Abundant evidence suggests that eating whole in fruits, vegetables and whole grains—all rich in networks of naturally occurring antioxidants and their helper molecules—provides protection against free radicals.
  • Getting Enough Sleep.
  • Avoid Sugar.
  • Don't smoke.
  • Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.
  • Try to minimize stress.
  • Drink enough water to keep your body hydrated.
  • Avoid excess alcohol.
  • Regular physical activity (outdoor activities may not be allowed in countries with 'lock-down').


Recent concerns that common antihypertensive drugs may have a negative effect in COVID-19 patients are not supported by solid evidence, report scientists in a new review published in Mayo Clinic Proceedings. Evidence suggests that ACE inhibitors and angiotensin receptor blockers may improve outcome in COVID-19 hypertensive patients.

If you have high blood pressure, do make sure that your blood pressure is well controlled, as the fever will likely to increase your blood pressure, raising your probability of getting a heart attack or a stroke. 

Be safe and stay at home!


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