Best supplements for COVID-19: the scientific research on quercetin and COVID-19

Introduction to quercetin

Quercetin is a type of nutrient called a flavonoid. Among the flavonoids, the effects of quercetin has been most extensively investigated.


Quercetin is naturally found in small amounts in many plant foods such as tea, red wine, onions, apples, and berries. Modern research has demonstrated the safety and effectiveness of quercetin supplements for a range of health complaints. Therefore, if someone is looking for a health benefit from quercetin, a supplement may be necessary...


Summary of COVID-19 and quercetin

As of writing (March 2022), there are:

  1. 2 scientific publications regarding quercetin supplementation and COVID-19 prevention
  2. 4 scientific publications regarding quercetin supplementation in COVID-19 patients


The 2 prevention studies did indeed report a decreased risk of COVID-19 infection! In addition, all 4 studies with quercetin supplementation reported reduced COVID-19 severity within a period of just 14 to 30 days, including:



COVID-19 and quercetin: Lab studies


COVID-19 and quercetin: Scientific reviews

Quercetin is a flavonoid with many biological effects, including antioxidant, anti-inflammatory, and antiviral effects. It has anti-infective and anti-replicative effects on a number of viruses, including RNA viruses (COVID-19 is an RNA virus). In addition, quercetin’s anti-inflammatory properties may have beneficial effects in respiratory viral infections, including. Studies have suggested that quercetin can modulate the cytokine release pattern associated with inflammation. 


Quercetin works best with other specific nutrients!

Piperine is a major alkaloid present in black pepper. Indeed, piperine can increase the absorption and bioactivity of quercetin.


Many studies have demonstrated that the combination of quercetin with another nutrient called curcuminoids is stronger than that of either individual treatment alone.


And further, a 2016 study published in the Journal of Complementary and Integrative Medicine demonstrated that the combination of quercetin  with both piperine and curcuminoids seems to have the greatest synergy and result in the greatest absorption and bioactivity.


COVID-19 and quercetin: Human studies 

But we always want to look for human studies. Now I will introduce and summarise the 2 publications regarding quercetin supplementation and COVID-19 prevention and the 5 publications regarding quercetin supplementation in COVID-19 patients: 


Human study 1: COVID prevention

-The first ever study investigating quercetin supplementation and COVID-19 prevention

-December 2021

-Published in the academic journal Journal of Evidence-Based Integrative Medicine

 -This study included 113 people at risk of COVID-19 infection:

  • 53 supplemented with the quercetin containing product
  • 60 did not

Over the 20 week study period:

  • less than 4% of the supplement group got flu-life symptoms compared to 20% in the non-supplemented group
  • none of the supplement group was COVID positive compared to 15% in the supplemented group! 


The authors concluded:

'Offering a low cost, readily implemented anti-viral approach, the study regimen may serve as a useful tool in combatting the pandemic'


Human study 2: COVID prevention

-January 2022

-Published in the academic journal Life

 -This study included 120 Healthcare Workers.

-60 were assigned to quercetin supplementation and 60 were assigned to placebo and all subjects had COVID tests every 3 weeks.


Over the 3 this 3 month study, there was 75% less COVID infection in the quercetin supplemented group!


The authors wrote:

'those who had taken the quercetin supplement had a protection factor of 14% more to not contract the COVID-19 infection than that of those who had taken a placebo'


Human study 1: COVID treatment

-The first ever study investigating quercetin supplementation in COVID-19 patients:

-June 2021

-Published in the academic journal International Journal of General Medicine

 -This study included 42 patients with COVID-19. 21 patients were treated with standard medical care and 21 were treated with quercetin supplementation + standard medical care.


After only 7 days:

-16 patients in the quercetin group tested negative for COVID-19 compared to only 2 in the standard medical care group

-12 patients in the quercetin group had improved symptoms compared to only 4 in the standard medical care group.


In addition, the COVID-19 patients who consumed quercetin had:

  • Less inflammation in their blood (LDH, ferritin and CRP)
  • Less blood clotting in their blood (D-dimer)


The authors concluded that:

'Quercetin shortens the time of testing from positive to negative, reduces symptoms severity and negative predictors of COVID-19'


    Human study 2: COVID treatment

    -June 2021

    -Also published in the academic journal International Journal of General Medicine

     -This study included 152 patients with COVID-19. 

     -After only 30 days, the COVID-19 patients who consumed quercetin had:

    • Less frequency and length of hospitalization
    • Less need of oxygen therapy
    • Less progression to the intensive care unit (ICU)
    • Less deaths

    In addition, quercetin had benefits for fatigue and appetite!


    The authors concluded that:

    'Quercetin is a safe agent and could aid in improving the early symptoms and help in preventing the severity of COVID-19 disease'


    Human study 3: COVID treatment

    -August 2021

     -This study included 429 patients with COVID-19 and at least one underlying condition

     -After only 7 days, the COVID-19 patients who consumed quercetin had:

    • Less inflammation (CRP and ferritin)
    • Improved immune function (higher lymphocyte count)
    • Improved breathing and lung function


    The authors wrote:

    'The quercetin supplement group had more advanced lung function and had positive effect on laboratory recovery/results'


    Human study 4: COVID treatment

    -January 2022

    -Published in the academic journal European Journal of Pharmacology

    -This study included 60 patients with severe COVID-19. All patients received powerful antiviral medications (remdesivir or favipiravir) ,while have also received quercetin supplementation.


    After only 7 days, the COVID-19 patients who consumed quercetin had:

    • Earlier discharge from hospital
    • Less inflammation (CRP, LDH, ALP)
    • An increase in haemoglobin level
    • Improved breathing


    The authors wrote:

    'Quercetin is safe and effective in lowering inflammation as critical markers involved in COVID-19 severity'



    The use of quercetin supplementation for COVID is supported by:

    • scientific reviews
    • lab studies
    • 2 prevention studies in humans
    • 4 treatment studies in humans

    Since quercetin supplements are widely available and safe, quercetin supplementation is a great strategy to help prevent and treat COVID!


    An ideal quercetin supplement would contain

    • Piperine which can increase the absorption and bioactivity of quercetin
    • Curcuminoids which have synergystic effects with quercetin

    In addition to quercetin, other supplements and nutraceuticals backed by scientific evidence to help with COVID-19 include:


    The best scientific evidence we have suggests that regarding COVID-19 infection, earlier supplementation is better


    *Full references list and full text manuscripts available upon request

    Written by our founder, Dr. Conor Kerley

    Copyright of Phytaphix  

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