It’s that time of year again. The time when viruses of all kinds are spreading in schools, work, and at home. Some of these viruses can be annoying, while others can lead to dangerous health complications and worse. We try to stay healthy by taking vitamins and washing our hands, but we end up getting sick anyway. Taking a quercetin supplement might be one supplement that can help protect us from these viruses.
What is Quercetin
Quercetin is one of the thousands of phytochemicals found only in plant foods. It belongs to a group of phytochemicals called flavonoids and is a powerful antioxidant that protects our cells from becoming damaged by free radicals. You can get plenty of quercetin by eating these foods:
- Onions, especially red and yellow onions
- Spring onions
- Apples
- Kale
- Blueberries and cranberries
- Broccoli
- Tomatoes, especially cherry tomatoes
- Green tea and black tea
- Hot peppers like Ancho, yellow wax, and chili peppers
- Cocoa
What is a Virus
A virus will have a genome and a surrounding shell made of protein (capsid). This is what helps a virus latch onto cells. Some viruses have a greasy shell, called an envelope, made from membranes of the last cell they infected.
The viruses that have this greasy shell include coronaviruses like Covid-19 infection, flu virus, hepatitis C, herpes virus, and HIV. Soap disrupts this greasy membrane, which is why it is so important to wash your hands, face, and masks with soap and water.
How a Virus Attacks Our Body
Once inside us, the virus tries to invade our cells. If they can enter a cell, they can then use those cells to reproduce and multiply into more and more virus replications. Different viruses attach to different cells in our body.
Our immune system will recognize a virus as a foreign invader and attack it. Viruses can replicate fast, and hopefully, our immune system can attack them even faster. This is why it is important for us to have a strong immune system and a healthy gut microbiome. A strong immune system can fight off a viral infection by enhancing our immune response to viruses.
Can Quercetin Stop Virus Replication
A 2012 study with mice published in Phytotherapy Research found that quercetin reduced the symptoms and severity of influenza. Mice were given quercetin for six days after being infected with the influenza A virus had a much higher survival rate.
Also reported in this study, the viral concentration in the lungs of these mice was 2,000 times lower than the levels in the mice treated with a placebo, and two times lower than the mice that were treated with Oseltamivir, better known as Tamiflu. [2]
A 2010 randomized, double-blinded, placebo-controlled trial published in Pharmacology Research looked at how 500 mg and 1000 mg doses of quercetin taken for twelve weeks affected those with upper respiratory tract infections.
They found that those who were 40 years of age and over and in good physical shape had a significant 36 percent reduction in the severity of the upper respiratory tract infections, and a 31 percent reduction in sick days due to a respiratory infection when compared to those that received the placebo.
The study went on to report that these reductions only occurred in those that they were physically fit, ate more fruits and vegetables, exercised, and had a low body mass index (BMI). [3]
This could be because a plant-based diet full of fruit and vegetables are also high in healthy phytochemicals like quercetin.
Can Quercetin Prevent Covid-19
Covid-19 is also called SARS-CoV-2 because it is thought to be similar to the SARS virus that caused the pandemic of 2003 since they are both a type of coronavirus. During the SARS pandemic, scientists did find that quercetin was able to block SARS-Coronavirus entry into Vero E6 cells. [4]
“Quercetin displays a broad range of antiviral properties which can interfere at multiple steps of pathogen virulence -virus entry, virus replication, protein assembly- and that these therapeutic effects can be augmented by the co-administration of vitamin C.”
As of October 2020, researchers found that quercetin supplementation has a theoretical but significant capability to interfere with Covid-19 (SARS‐CoV‐2) replication. Their results found quercetin to be the fifth best compound out of the 18 studied so far.
I could not find a list of all of the 18 compounds, though melatonin is mentioned in recent studies as another compound that might prevent SARS-CoV-2. [5]
Most studies found that taking vitamin C with quercetin helped quercetin to be better absorbed by our bodies.
Since the outbreak of the SARS CoV 2 infection, there have been several clinical trials with covid patients. One such clinical trial in 2021 found that supplementation with Quercetin Phytosome® (QP), a new bioavailable form of quercetin, caused a shorter time for the virus to clear the body, milder symptoms, and a higher probability of an earlier resolution of the disease [9].
Other Deadly Viruses
Studies have shown that quercetin could also have antiviral properties against other deadly viruses that include:
- Ebola [6]
- HIV [7]
- Hepatitis C virus (HCV) [8]
More Health Benefits of Quercetin
In addition, quercetin has other health benefits that include:
- Prevents and suppress chronic inflammation that leads to damaged endothelial cells and heart disease
- Has anti-tumor and anti-cancer properties
- Improves circulation in the brain
Not A Vaccine Substitute
Now that there are vaccines available for Covid-19 (SARS-CoV-2), it is recommended that you get a vaccine. Quercetin can still protect you from viral replication, but nutrients or supplements are not a substitute for a vaccine.
Summary
The Covid-19 pandemic has raised awareness and interest in any compounds that can prevent and treat viruses. Even with a Covid-19 vaccine, there will be continuing studies to determine if Quercetin can be used as a possible compound to prevent and treat it.
As always, it is best to eat a healthy diet that includes all types of plant foods. These foods contain phytochemicals that keep your immune system and gut microbiome healthy. And a healthy immune system is the best way to fight off viruses and other diseases.
About The Author
Sam Montana is a certified Food Over Medicine instructor from the Wellness Health Forum Center and certified in optimal nutrition from the Harvard T.H. Chan School of Public Health.
© 2020 Sam Montana/Healthy Food and Life
References:
[1] Front. Immunol., 19 June 2020
| https://doi.org/10.3389/fimmu.2020.01451
[2] Choi HJ, Song JH, Kwon DH. Quercetin 3-rhamnoside exerts anti-influenza A virus activity in mice. Phytother Res. 2012 Mar;26(3):462-4
[3] Pharmacology Research
[4] Front. Immunol., 19 June 2020 | https://doi.org/10.3389/fimmu.2020.01451
[5] Cleveland Clinic: Melatonin
[6] American Society for Microbiology DOI: 10.1128/AAC.00530-20
[7] Quercetin Naturally Blocks HIV
[8] Nature: Effect of Quercetin on Hepatitis C Virus Life Cycle: From Viral to Host Targets
