Taken from chapter 3.7 of the book Live Young, Longer, by Eric Simard, 2016.
In the past few weeks, quercetin has been presented as a drug that could help fight the coronavirus. This is very interesting news, but the most interesting is that you can eat it every day, in a wide variety of vegetables.
La Press talked about it on February 22nd (Coronavirus: Montreal researchers want to test a drug in China (French only)) and on Radio-Canada on February 24th (A plant substance to get rid of the coronavirus? (French only)), on the 27th (Misleading advertising on the quercetin and coronavirus (French only)) and on February 29th (Coronavirus: quercetin tested in China (French only)). The strangest thing is that it is not mentioned that it is one of the molecules present in large quantities in a diet rich in vegetables. Quercetin is even the flavonoid, a family of polyphenols, the most consumed in human food. Here are some explanations about this beneficial molecule that is attracting a lot of interest.
In which foods can you find quercetin?
Quercetin is found in several plants, such as citrus fruits, capers, cocoa, and ginkgo biloba. It is very present in our diet. It is estimated that the average American consumes about 25 mg per day of quercetin. In fact, it is the most important flavonoid in terms of quantity in human nutrition. Good news, it has extraordinary health benefits.
Foods considered rich in quercetin (they contain more than 0.50 mg per 100 g) are apples, grapes, onions, artichokes, fennel, celery, beans and chickpeas, plums, turnips, peppers, strawberries, tomatoes and broccoli.
It is important to emphasize that quercetin is sensitive to temperature. For example, onions and tomatoes will lose between 75 and 80% of their initial quercetin content after boiling for 15 minutes, around 65% after cooking in the microwave and 30% after frying. Since quercetin degrades during cooking, it is interesting to eat these vegetables raw in order to preserve their content.
Quercetin and aging
As you know, my area of expertise is healthy aging (www.esimard.com) and I mentioned quercetin in my first book in the context of molecules to fight the effects of aging.
In 2015, a team of scientists carried out a comprehensive review of the literature on natural molecules with anti-aging effects. Among the 32 natural compounds considered, quercetin is one of the molecules accumulating the most results regarding its anti-aging effects (with resveratrol and polyphenols in olives). This molecule, found in a large number of vegetables, has demonstrated beneficial effects on aging and life expectancy in three different study models.
Other health benefits
Quercetin is mainly used as a supplement in traditional medicine for its antiallergic effect (it would therefore have an effect on the immune system since allergies are a disproportionate reaction of the immune system). More specifically, it inhibits the inflammatory processes attributed to activated neutrophils (the body’s first line of defense), by stabilizing the membrane, its powerful antioxidant effects and the inhibition of the hyaluronidase enzyme. Quercetin is identified as a molecule with great potential for diseases and risk factors associated with aging. Among these physiological effects reported in the scientific literature, the following effects are noted (N.B.: These effects are not all supported by sufficient evidence to affirm that they are significant in humans):
• preventive against infections;
• anticancer and preventive;
• blood pressure reducers;
• reduces blood glucose levels;
• inhibitors of the replication of several types of viruses.
The recommended dose would be 250 to 600 mg, three times a day, to decrease allergy symptoms like those of rhinitis (irritation of the nasal mucosa). With 22 mg per 100 g of onions, we quickly understand that the recommended dose is high compared to its availability in food. Capers contain 233 mg/100 g.
What about the coronavirus?
The antiviral effects of quercetin are documented for different types of viruses, both to prevent their replication, the production of viral molecules and the ability of viruses to infect. Quercetin also has beneficial effects on the functioning of the immune system. These multiple mechanisms of action could apply to the coronavirus. As mentioned by Dr. Michel Chrétien, this is a recent discovery that needs to be tested as a clinical study.
In addition, the risk/benefit balance must be taken into account. For a completely risk-free product (such as quercetin), the potential benefit of which is very high (preventing or treating coronavirus infections), the sum of scientific demonstrations need not be very high to justify a therapeutic approach. In addition, it is possible to simply promote greater food intake of vegetables rich in quercetin.
Other natural molecules are also known for their antiviral or antimicrobial effects. For example, melatonin is also a natural substance that is considered for the treatment or prevention of certain viral infections, including that of the Ebola virus. Should we consume it for this reason? Our risk of getting Ebola is practically zero.
Quercetin has a large number of health benefits. Enriching our diet with vegetables rich in quercetin can only be beneficial (a soup recipe in our blog: Green tea soup, turkey and vegetables rich in quercetin), but this is not necessarily what will protect you from coronavirus. The taking of a supplement is not yet justified either by the scientific literature or by the current risk of contamination in Quebec.
The health of your immune system depends on a multitude of factors, the most important of which are sleep quality and stress reduction (Immune System and Aging). It makes a lot more sense to focus your energies on making sure you have good lifestyles habits that will give you a healthy immune system ready to handle any eventuality.
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