Quercetin, Bromelain and NAC for COVID

Quercetin, a natural anti-oxidant, anti-inflammatory and anti-blood clot compound contained in abundance in various fruits and vegetables, is a zinc ionophore. The major benefit of taking quercetin with zinc is that the quercetin will push the zinc into the center of the cell where the zinc can stop the virus from reproducing.

Additionally, Quercetin has been shown to be a potent inhibitor of coronaviruses by inhibiting cellular entry as well as inhibiting proinflammatory cytokines. One of the hallmarks of COVID-19 is an imbalanced immune response cascading to cytokine storms and then hyper inflammation which then can lead to acute respiratory distress syndrome (ARDS). 

Quercetin has been shown to inhibit proinflammatory cytokine production as well as inflammation due to its antioxidant properties, amongst others. By inhibiting destructive inflammation and potentially the entire cascade, quercetin may prevent severe damage to the respiratory system amongst other organs (source). 

Recent clinical trial data shows that the combination of Vitamin C and Quercetin provided strong preventative protection against COVID-19 infection of healthcare workers when compared to the control group as shown below (source). Specifically, 1.4% (1 out of 71 healthcare workers) of healthcare workers using Quercetin and Vitamin C combination were infected with COVID-19 vs. 21.4% (9 out of 42 healthcare workers) of healthcare workers in the control group were infected with COVID-19 (Total Subjects, n = 113).


Elderberry, red onions, white onions, cranberries and green tea are among the richest sources of dietary quercetin.

As of November 2021, there have been 5 published studies of quercetin against COVID-19. For the list of studies, check out c19quercetin.com.

For clinical trials, more than 10 studies have been launched to investigate the benefits of quercetin against COVID-19. Ultimately, the results of the above trials will offer more definitive evidence.
NAC (N-Acetyl Cysteine) is a precursor to glutathione. It is an antioxidant and increases glutathione levels in the body (Source). NAC has mucolytic activity, so it helps reduce respiratory mucus levels. Laboratory research suggests that NAC might boost immune system function and suppress viral replication. NAC also decreases levels of interleukin-6 and has other anti-inflammatory effects.

NAC inhibits cellular entry and replication of some respiratory viruses, assists in clearing thickened mucous from the airways, suppresses inflammatory signalling, and may help mitigate viral infection-induced cytokine storm (Ref). NAC may also protect against coagulation problems associated with COVID-19, as it has both anticoagulant (source) and thrombolytic effects (source), meaning it may both prevent clots and break up clots that have already formed.

Glutathione is also one of the natural blood thinners as it is known to reverse the build-up of plaque and lessen the tendency of abnormal blood clots.

Why are some retailers and Amazon no longer selling NAC? The US FDA made it clear in 2020 that it considers NAC to be a drug and not a dietary supplement, so, for legal reasons, some companies have stopped selling it in United States.

As of November 2021, there have been more than 10 published studies of NAC against COVID-19. For the list of studies, check out c19nac and 19 studies involving NAC for COVID-19 are listed on Clinicaltrials.gov.


Bromelain, or pineapple extract, is a compound made up of proteases normally found in pineapples. Although it is widely known for its ability to aid in digestion and protein breakdown, its use far transcends these functions and can actually offer a lot more. The good news is that it's available in the market as a supplement and as an aid for disease treatments.

The history of bromelain is heavily linked to pineapple because it is the only known major source for this group of enzymes. Its first primary source was the pineapple fruit, before it was discovered that the mature pineapple stem had much more concentrated bromelain content.

Through the years after its discovery, the production of bromelain has broadened. Its commercialization has led manufacturers into developing faster extraction techniques for large-scale production and purification. Today, bromelain supplements are used for numerous health approaches.

These uses have been observed to be dependent on the time when it is taken. For example, if taken after a meal, bromelain may help promote better digestion and absorption, but when taken on an empty stomach, it can help alleviate inflammation (Daily Mail).

Quercetin was initially found to provide broad-spectrum protection against SARS coronavirus in the aftermath of the SARS epidemic that broke out across 26 countries in 2003. Now, some doctors are advocating its use against COVID-19, in combination with Bromelain and vitamin C.

Quercetin helps zinc by acting as a zinc ionophore (PubMed 2014), the same mechanism of action that hydroxychloroquine has via helping zinc pass the cell wall where it might halt viral replication.

This zinc ionophore activity of quercetin facilitates the transport of zinc across the cell membrane. It is known that zinc will slow down the replication of coronavirus through inhibition of enzyme RNA polymerase (PubMed 2010). 

The COVID-19 is an RNA (RiboNucleicAcid) virus and requires the RNA polymerase to replicate. Do take note that the study publication was a 2010 publication and is referring to a different coronavirus as compared to the latest coronavirus (COVID-19); though both are from the same family of coronaviruses.

Quercetin works best when taken with vitamin C and Bromelain, as vitamin C helps activate it and bromelain helps with the absorption.

Quercetin is also part of the FLCCC I-MASK+ protocol and Zelenko protocol for COVID-19.

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