Quercetin is a natural pigment found in a group of plant compounds called flavonoids. They are present in fruit, vegetables, teas and grains.

It is an antioxidant and plays an important role in helping our bodies combat free radical damage (free radicals are unstable molecules that cause cellular damage on too high levels). This is linked to chronic diseases such as heart disease, cancer, diabetes and degenerative brain disorders.

In addition, its antioxidant properties may help with:

  • fighting inflammation

  • allergy symptoms

  • high blood pressure

  • boosting immunity

  • aiding exercise performance

  • reducing high histamine symptoms

  • optimizing brain health

  • reducing cognitive decline

Foods rich in quercetin are red onions, bell peppers, apples, cooked asparagus, grapes, berries, broccoli,citrus fruits, cherries, green tea, coffee, red wine, and capers. If these are organically grown the quercetin level increases. It can also be taken as a supplement.


100 mg - 500mg 3 x a day. It is poorly absorbed so combine with vitamin C and /or bromelain to increase absorption. Bromelain is a supplement extracted from pineapples that is often used for burns or inflammation.

Safety and side effects:

As quercetin is found in many fruits and vegetables it is safe to consume.

As a supplement taking more than 1,000 mg of quercetin per day may cause mild symptoms like headaches, stomach aches, or tingling sensations

For pregnant and breastfeeding women increase quercetin rich foods in the diet. Studies on the safety of quercetin supplements for pregnant and breastfeeding women are lacking so you should avoid taking quercetin as a supplement

Consult your doctor before taking quercetin, as it can interact with some medications, including antibiotics and blood pressure medications

Quercetin and Covid-19:

After the 2003 SARS-CoV-1 coronavirus outbreak researchers in China found quercetin bound to the spike protein of the virus, interfering with its ability to infect host cells.

This study led researcher Hasan Önal, MD to conduct an randomized control trial in Turkey examining quercetin's role in COVID-19. In the trial, 95 patients with COVID-19 are receiving a 1,000-mg active treatment dose and 113 healthcare workers are receiving a 500-mg dose as prophylaxis. In both treatment arms, quercetin is administered with vitamin C and bromelain.

Paul E. Marik, MD, chief of pulmonary and critical care medicine Virginia Medical School, Norfolk Marik included quercetin in the institution's COVID-19 management protocol for prophylaxis and for mild to moderate cases. Stating "If you have something that is potentially beneficial, safe, and cheap, what do you have to lose?"

He agreed that before widely administering quercetin to patients with COVID-19, it should be tested in a randomised controlled clinical trial.

Researchers at the Montreal Clinical Research Institute are awaiting approval for a clinical trial testing quercetin for the treatment of COVID-19.


Quercetin is found easily in a variety of foods and is safe to take as a supplement. I t has proven benefits as an anti inflammatrant and in reducing high histamine levels as well as improving cognitive function. I think it is very well suited to those with Long Covid.

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