Quercetin - an antioxidant with versatile effects

Quercetin - what is it?

Quercetin is a compound belonging to plant flavonoids, and more specifically to the group of flavonols. It occurs in plants as their natural dye (it usually takes on a yellow or white color), protects them from the harmful effects of UV radiation, acts as an antifungal, and attracts insects, promoting plant pollination.

Quercetin, whose chemical formula is C15H10O7, can occur as a glycosidic derivative or in the free state. It is obtained by crystallization from plant extracts.

Quercetin glycoside is fat-soluble and well soluble in water, compared to its free form, which is poorly soluble in H2O. The glycosides that contain quercetin include rutin.

Interestingly, the name of the compound comes from Latin and means oak forest. This is because quercetin is also found in oak bark.

Sources of quercetin

Since quercetin is one of the most important flavonoid compounds, it is commonly found in many foods of plant origin. It can be found in fruits and vegetables including capers, red onions, apples, cranberries and lettuce. Among its sources we can also include elderberry fruit, sorrel and fruit juices.

Quercetin is also found in spices such as lovage, dill, dried oregano, ginger and parsley, as well as in green tea.

The amount of quercetin supplied to the body with food products is hard to determine unequivocally, as it depends, among other things, on environmental factors accompanying plant growth, such as sunlight and temperature.

However, an increase in the concentration of the compound was observed with fruit ripening, so we can conclude that very ripe fruits are a better source of quercetin than unripe ones.

Quercetin - action

Quercetin is used to dye cotton and as a reagent in chemical analysis. It has a lot to offer plants, as well as people. Due to its antioxidant properties, it protects the body from the harmful effects of free radicals, and also aids in the treatment of many diseases.

Antioxidant properties

Since quercetin exhibits antioxidant properties, its main action is antioxidant activity, which neutralizes free radicals. Thus, this compound reduces oxidative stress and inhibits oxidative damage to protein and lipid structures. Thanks to this quercetin reduces the risk of diseases caused by mutations in the DNA code.

Anti-allergic effect

Quercetin is a compound used in reducing allergies. Together with calcium salts, it helps fight unpleasant ailments. Calcium alone is not suitable for monotherapy, but it can be used supportively, as a means of relieving allergy symptoms, i.e. runny nose, rash or watery eyes. Quercetin additionally inhibits the secretion of inflammatory reaction mediators, among others histamine release, thus limiting the development of an allergic reaction. This compound is helpful in the treatment of allergies to animal hair, pollen or dust.

Anti-inflammatory effect

It is also possible that quercetin has an anti-inflammatory effect by affecting the activity of cyclooxygenases and, consequently, inhibiting the production of PGE2, or prostaglandin-2, which is involved in inflammatory processes.

Quercetin can reduce existing inflammation in the body and reduce the risk of creating new inflammatory processes by inhibiting the formation of pro-inflammatory cytokines.

Anti-atherosclerotic effect

Studies have shown that a diet rich in flavonoids (including quercetin) helps reduce the incidence of cardiovascular-related diseases. Thus, quercetin contributes to lowering LDL cholesterol ("bad") and regulating total blood cholesterol levels. In addition, the compound can strengthen blood vessels and improve their elasticity, as well as have a positive effect on blood pressure. Therefore, the substance may have a beneficial effect on the cardiovascular system, protecting against cardiovascular disease and reducing the risk of atherosclerosis.

Antibacterial and antiviral properties

Scientific data also suggest that quercetin exhibits antibacterial and antiviral properties.

This compound has the ability to bind to the proteins of the virus coat, thanks to which it inhibits the activity of microorganisms. It has also been observed that quercetin has a positive effect on reducing the risk of infections and the healing process.

Quercetin and weight loss

Quercetin seems to be helpful in reducing excessive body weight. Studies conducted so far suggest that the compound has the ability to induce apoptosis, or the natural death of fat cells, as well as the ability to inhibit the formation of new fat cells.

It also affects the growth of lipolysis, which is an enzymatic process of hydrolytic decomposition of triglycerides, i.e. supports fat burning. Although it does not exhibit weight-loss properties on its own, it can help get rid of excess weight.

Other properties of quercetin

Thanks to its versatile action, the substance is also used in the treatment of asthma, as well as in reducing the symptoms associated with prostatitis. Quercetin has a positive effect on intestinal function and vision, reducing the risk of developing glaucoma or cataracts. Occasionally quercetin is also used in cancer, but research is still ongoing on its effectiveness.

Due to its antioxidant properties, it helps take care of beauty by supporting the condition of hair and nails. Quercetin has anti-aging effects, reduces acne and improves skin condition. As a result, it is also used as an ingredient in cosmetics.

Quercetin in the form of dietary supplements

Quercetin can also be delivered to the body in the form of a dietary supplement. Preparations rich in this compound are most often used by people suffering from allergic rhinitis and allergies or among patients diagnosed with inflammatory bowel disease.

Providing the body with quercetin from natural food sources seems to be the best solution, but in the case of increased demand for this compound, commonly available supplementation comes with help. However, it should be remembered that it makes sense only when it is well thought out and individually matched to the needs of the body.

Since flavonoids are poorly soluble in water, it is recommended to take quercetin together with bromelain, which is beneficial for the synergy of their action and increases the absorption of the compound.

Recommended serving of the supplement

Every day with food we provide the body with about 20-40 mg of quercetin. In dietary supplements, the content of the compound varies and ranges between 50 mg and 500 mg.

However, there is still a lack of concrete scientific data suggesting what supply of quercetin is recommended, both for healthy people and those suffering from various ailments.

There are studies conducted on adults who took the supplement in the amount of 500-1000 mg every day for 12 weeks. Then, a reduction in upper respiratory tract infections was observed in people over 40 years of age. Studies have also been conducted on athletes, where already 100 mg of quercetin per day reduced morbidity.

Thus, it is difficult, without further research, to unequivocally determine the appropriate portion of a supplement that will produce a positive health effect on the human body.

Side effects and contraindications

Taking quercetin only from natural food sources is safe. Then it is difficult to talk about an overdose of the compound.

However, it is much easier to deliver excessive quercetin to the body with dietary supplements. Therefore, you should always follow the manufacturer's instructions on the product packaging and do not exceed the recommended amount of the supplement.

Consuming a dose higher than recommended may contribute to the occurrence of undesirable symptoms such as increased blood pressure, cardiac arrhythmias, nausea, vomiting and diarrhea.

Also, never use if you are allergic to any of the supplement's ingredients.

It is worth being careful when taking quercetin together with other drugs, as it may reduce absorption of the active substances of the preparations taken.

Since quercetin is included in the flavonoid group, it reduces blood clotting and dilates blood vessels. Therefore, people prone to hypotension or those with low blood clotting who are taking anticoagulants must be very careful about consuming products that are source of quercetin.

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Natalia Goździak

Copywriter - nutritionist. Bachelor's degree in sports dietetics She graduated from the Academy of Physical Education in Poznan, while her master's degree in dietoprophylaxis and dietotherapy - from the University of Physical Education in Poznan. at UP in Poznań. However, she treats the principles of healthy eating primarily as valuable guidelines, rather than strict rules that must be strictly followed. Knowledge in the field of copywriting, on the other hand, she draws from courses and industry literature, but since the best way to learn is to practice. learning is practice, she spends many hours each day playing with words and creating new, unique content. content. Privately, she is passionate about photography and can't imagine life without books.

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