Quercetin’s use in Covid-19 makes great sense, since it is both stabilizing to mast cells and anti-inflammatory.  Especially in more significant Covid-19 cases, there appears to be a component of mast cell activation, which perpetuates the inflammatory cascade.  For this reason, some clinicians are also using H2 and H1 receptor antagonists in their treatments as well.  Quercetin has been integral to the FLCC’s recommendations for prevention through all treatment stages since the beginning of the pandemic, and they have also been recommending famotidine, an H2 receptor antagonist (typically thought of as an “antacid,” but with more systemic effects on all the body’s H2 receptors), for all cases more severe than “mild.”

Mark Bricca, ND

Weil’s group as well as the IFM have had Quercetin on its list of supplements to take for COVID since the early days of the pandemic.   Good to see a clinical trial published in a peer-reviewed journal.

Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher

Yet another nutraceutical showed promise as at least a supportive treatment against SARS-Cov-2, the virus behind COVID-19. This time it’s the safe nutraceutical product known as quercetin, and the results certainly justify additional investigation via larger, better-designed randomized controlled trials. TrialSite reminds all the gratitude that should be bestowed on subjects in clinical trials, those who make the sacrifice to help deliver this important data. In this case, the inclusion/exclusion criteria would prompt many a subject to reject the trial during the informed consent discussion which included “Study participants from both groups were asked not to change their usual diet and to abstain, if possible, from dietary supplements containing lactoferrin, zinc, vitamin C and vitamin D for the duration of the study.” Of course, TrialSite has reported that at least some of these supplements demonstrate promising signs of efficacy in COVID-19 early treatment and even prevention. At a minimum, one doesn’t want to fall short in critical supplements while battling COVID-19. As a side benefit, quercetin shows promise as a senolytic and in idiopathic pulmonary fibrosis. 

This study was recently published in the peer-reviewed International Journal of General Medicine, and included a number of investigators from Italy, the UK, and Pakistan.  

The Treatment

Quercetin is a plant flavanol from the flavonoid group polyphenols. This substance is found in many fruits, vegetables, leaves, seeds, and grains, and even red onions and kale.  A bitter flavor, flavanol is used as an ingredient in dietary supplements, beverages, and foods.

The Results

Thanks to the TrialSite community member for sending in these impressive study results, albeit with some study design limitations. A randomized, prospective, open-label study of 152 COVID-19 outpatients, the study team treated the patients with a proprietary formulation of quercetin at a dosage of 1000mg/day for 30 days. The results showed a significant reduction in hospitalization, days hospitalized, need for supplemental oxygen, ICU, and mortality. The results also confirmed the very high safety profile of quercetin and suggested possible anti-fatigue and pro-appetite properties. This suggests there are symptomatic relief benefits as a justification to use quercetin as an adjuvant therapy while results from larger, better-designed RCTs are conducted.

The authors recognized the limitations of their study and called attention to the fact that the groups were not well matched with respect to comorbidities. To account for this, the authors included a sub-group analysis in Table 5 (follow the link) that excluded all patients with preexisting comorbidities from both groups. The benefits of quercetin are reduced but there is still a clear signal that should be investigated further.

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