There are several drug studies underway for treating COVID-19. Millions of dollars will be spent on drug studies. Yet there are several dietary supplements that are known to have anti-viral activity through several mechanisms. Some phytochemicals act as zinc ionophores. They facilitate entry of zinc into cells where zinc can block virus replication. Some phytochemicals (including those that act as zinc ionophores) can bind to the critical spike protein on the surface of COVID-19 which allows the virus to enter the cell. In addition there are many anti-inflammatory phytochemicals that could potentially mitigate the lethal cytokine storm that leads to multi-organ failure in the ICU, resulting in death. Some phytochemicals might have all three effects.
Despite the basic science that would support the potential use of these phytochemicals in the treatment of COVID-19, no clinical studies have been funded. They likely never will. The culture of medical research and practice in the US remains oriented towards drug interventions and surgery. Without a patent there is little profit in finding clinically effective, inexpensive and safe alternatives to drugs.
I have previously discussed EGCg (green tea extract) and quercitin as zinc ionophores. If you have not already read that discussion please go here.
Lets look at the second mechanism of action mentioned above, binding to the COVID-19 spike protein that facilitates cell entry.
Recently several NATURALLY occurring phytochemicals, found in vegetables, fruits, and tea, have been compared to two drugs under study for COVID-19 in terms of their ability to bind to the COVID-19 spike protein. The results are noteworthy.
“The computed activity of EGCG was found to be higher than that of both reference drugs, Remdesivir and Chloroquine”
So a naturally occurring substance found in green tea has greater binding affinity for the critical spike protein on COVID-19 then two leading drug candidates.
The image below shows the binding affinity of various phytochemicals for several COVID-19 surface protein domains (domains are areas on the protein where drugs and phytochemicals might bind and work). The phytochemicals appear in rank order. EGCg found in green tea and available as an extract in supplement form, binds to the viral protein more strongly than the drugs Remdesivir and Chloroquine.
EGCg also functions as a zinc ionophore, as does quercitin, which also binds to the critical COVID-19 spike protein. Remember, the virus must first enter the cell before it can replicate. If the virus cannot enter the cell, it cannot replicate. COVID-19 enters the cell when the surface spike protein on the virus binds to the ACE-2 receptor on human cells. These receptors are found in abundance in the nose, throat, and lung. (They are present on many other types of human cells as well) This binding/docking and entry process represents a major target for drug interventions.
Curcumin, which has anti-inflammatory activity (potentially mitigating a cytokine storm) has the second strongest binding among the many phytochemicals studied. And quercitin (another zinc ionophore) is not far behind.
You can read this study (a preprint which means it has not yet been peer-reviewed) here.
So both EGCg and quercitin have potential benefit by blocking the virus from entering the cell as well as facilitating zinc’s ability to block virus replication once the virus is inside the cell.
But that’s not all. Both of these supplements have anti-inflammatory activity.
“Dietary plant polyphenols such as the flavonoids quercetin (QCT) and epigallocatechin-gallate act as antioxidants and as signaling molecules.”
And the cytokine storm that can be lethal with COVID-19 is an inflammatory reaction.
Quercitin is the most abundant polyphenol found in foods:
| FOODS | QUERCETIN (MG/100G) |
|---|---|
| capers, raw | 234[6] |
| capers, canned | 173[6] |
| dock like sorrel | 86[6] |
| radish leaves | 70[6] |
| carob fiber | 58[6] |
| dill | 55[8] |
| cilantro | 53[6] |
| Hungarian wax pepper | 51[6] |
| fennel leaves | 49[6] |
| onion, red | 32[6] |
| radicchio | 32[6] |
| watercress | 30[6] |
| kale | 23[6] |
| chokeberry | 19[6] |
| bog blueberry | 18[6] |
| cranberry | 15[6] |
| lingonberry | 13[6] |
| plums, black | 12[6] |
EGCG is found in green tea but has low bioavailability.
EGCG in very high doses can cause liver toxicity. From WIKIPEDIA:
A 2018 review showed that excessive intake of EGCG may cause liver toxicity.[15] In 2018, the European Food Safety Authority stated that daily intake of 800 mg or more could increase risk of liver damage.[16] The degree of toxicity varies by person, suggesting that it is potentiated by genetic predisposition and the diet eaten during the period of ingestion, or other factors.[17]
A typical 400 mg capsule of green tea extract contains 200 mg of EGCg, so if you decide to take some, read the labels carefully to avoid taking too much. If you like to drink green tea:
A single cup (8 ounces or 250 ml) of brewed green tea typically contains about 50–100 mg of EGCG.
Part 2 of this series will discuss the cytokine storm, glutathione our body’s major anti-oxidant, and potential strategies to mitigate the lethal excessive inflammatory spiral of a cytokine storm.
But remember, there are many lifestyle choices we make that can protect us against any viral infection:
- Avoid alcohol consumption (alcohol wreaks havoc with your immunity)
- Get plenty of sleep (without adequate sleep your immune system does not work well )
- You must follow good sleep habits
- Exercise, especially out of doors in a green space, supports the immune system
- Get some sunshine and make sure you have adequate Vitamin D levels.
- Eat an anti-inflammatory diet rich in micronutrients.
- Practice stress reduction like meditation and yoga which improves the immune system
THIS WEBSITE PROVIDES INFORMATION FOR EDUCATIONAL PURPOSES ONLY. CONSULT YOUR HEALTH CARE PROVIDER FOR MEDICAL ADVICE.
Eat clean, drink filtered water, love, laugh, exercise outdoors in a greenspace, get some morning sunlight, block the blue light before bed, engage in meaningful work, find a sense of purpose, spend time with those you love, AND sleep well tonight.
Doctor Bob
Practical Evolutionary Health 
If EGCG in green tea, while at 50-100 mg per cup (250 ml) is not readily bio-available, and will not therefore bind to the dreaded spike proteins, what’s the point of drinking it?
Bioavailability is low but not zero. https://pubmed.ncbi.nlm.nih.gov/?term=egcg+bioavailability
The more important discussion is around lifestyle interventions that clearly reduce risk, not only for COVID19 but for chronic disease. Thanks for raising the question of bioavailability, which is important. Many of the beneficial effects of micronutrients are related to upregulation and downregulation of genes and biochemical processes, which can occur at low blood or tissue levels. Many factors affect bioavailability. Many beneficial affects of micronutrients occur downstream via metabolites, effects on the gut microbiome, and even metabolites of gut microbiota. This is a complex topic. There are many association-epidemiologic studies that support potential beneficial effects of catechins and their metabolites, despite low bioavailability. (Yes association does not equal causation…) But plausible mechanisms have been revealed by way of in-vitro studies. I recommend the review of EGCG at consumerlab.com, subscription is very inexpensive.
Thanks for the comment.