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Quercetin - What Is It, Benefits, Side Effects & Dosage [Complete Guide]

Updated: Jul 18, 2021

Quercetin seems to be a beneficial supplement since it has the potential to decrease inflammation while also acting as a powerful antioxidant.

Quercetin is a flavonol derived from plants that belongs to the flavonoid family of polyphenols.

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Table of Contents:


What Is Quercetin

Quercetin is a plant flavonol (also known as a flavonoid, bioflavonoid or pigment), which is a kind of polyphenol that belongs to the flavonoid group of polyphenols.

Quercetin is a type of plant flavonoid.

Flavonoids appear naturally in:

  • Fruit (commonly apples, berries & grapes)

  • Vegetables (commonly broccoli, onions and kale)

  • Grains

  • Tea

  • Wine

Capers also contain a significant amount of quercetin.

In many ways, quercetin is comparable to curcumin in that it offers a wide range of advantages, including lowering the risk of heart disease, cancer, brain illness, and other inflammatory disorders. (Source)

Quercetin offers many health advantages, the majority of which are derived from its capacity to act as a strong antioxidant and anti-inflammatory in the body. (Source)

Antioxidants are substances that have the ability to neutralise free radicals.

Free radicals are highly unstable molecules that wander throughout the body in search of additional electrons to form a pair with.

If left uncontrolled, these free radicals have the potential to cause damage to cells, proteins, and DNA.

The damage produced by these free radicals may result in a variety of chronic inflammatory disorders, including cancer, heart disease, brain disease, diabetes, and other diseases and ailments. (Source)

Food Sources Of Quercetin:

  • Apples

  • Grapes

  • Berries

  • Citrus Fruits

  • Cherries

  • Capers

  • Broccoli

  • Onions

  • Green & Black Tea

  • Coffee

  • Red Wine

See more sources of quercetin here.

Quercetin is a flavonoid that is present in high concentration in the human diet.

The typical individual eats about 10-100mg of quercetin per day, which comes from a variety of foods and beverages. (Source)

It is also available as a dietary supplement in the form of powder and capsules.

Reasons people take quercetin:

  • To Support General Health

  • To Reduce Allergies

  • To Boost Immunity

  • To Reduce Inflammation

  • To Improve Exercise Performance


Quercetin is a kind of flavonoid that has been shown to have significant anti-inflammatory and antioxidant effects.

It may be found in a variety of common foods and beverages, and it can also be taken as a dietary supplement.

quercetin supplements
Quercetin can be found in many foods and also taken as a supplement.

How Does Quercetin Work

Quercetin's main mode of action is to act as an antioxidant.

An antioxidant is a substance that neutralises free radicals, which are unstable chemical byproducts that damage cells and DNA, resulting in the development of chronic health problems.

Quercetin also contains a variety of additional characteristics, the most notable of which are its antihistamine and anti-inflammatory capabilities.

It also seems to have other functions:


Quercetins Benefits

Quercetin offers a plethora of advantages that are linked with its consumption.

Listed below are the top eight benefits of taking quercetin.

Click to skip to the benefits below or continue to scroll down.

Top 8 Quercetin Benefits:

  1. Reduces Risk Of Cancer

  2. Reduces Risk Of Brain Disease

  3. Reduces Risk Of Heart Disease

  4. Reduces Risk Of Diabetes

  5. Reduces Inflammation

  6. Reduces Symptoms Of Allergies

  7. Improves Exercise Performance

  8. Helps Slow Ageing


1) May Reduce Risk of Cancer

Because of quercetin's main function as a potent antioxidant, it may also possess anticancer effects in certain cases. (Source)

The antioxidant quercetin has been shown to inhibit cellular growth and induce cell death in prostate cancer cells in both laboratory and animal studies. (Source)

There is other research that has found quercetin to have comparable effects on the cancer cells listed below: (Source, Source)

  • Liver & Lung Cancer Cells

  • Breast, Bladder & Blood Cancer Cells

  • Colon, Lymphoid, Ovarian & Adrenal Cancer Cells

Interestingly, quercetin may increase tumour growth in women with estrogen-dependent breast cancer. (Source)

Because of an insufficiency of human research, quercetin is not utilised as an alternative cancer therapy and cannot be suggested as an alternative treatment either.


Preliminary study into quercetin's potential as an anticancer drug has shown encouraging findings, particularly in terms of lowering cancer risk.

However, owing to a lack of human trials and contradictory results, it cannot yet be suggested as an alternative cancer therapy.

quercetin cancer risk
Quercetin has shown promise in reducing the risk of certain cancers.

2) May Reduce Risk of Brain Disease

Quercetin's antioxidant and anti-inflammatory qualities may also be beneficial in the prevention of degenerative neurological brain disorders such as Alzheimer's disease and dementia, according to research. (Source)

The use of a high-quercetin diet was shown to reduce Alzheimer's disease indicators and enhance brain function in rats during the early-middle stages of the illness.

Curiously, this high-quercetin diet had no impact on rats suffering from Alzheimer's disease in the middle-to-late stages of the illness. (Source)

Mice with Alzheimer's disease were used in another study, and they were given a quercetin injection every two days for three months.

After three months, the mice demonstrated improved cognition on learning tests, and several of the indications of Alzheimer's disease were reversed. (Source)

Coffee is a beverage that has been associated to a lower risk of Alzheimer's disease.

According to research, quercetin is the main component in coffee that is responsible for the beverage's preventive properties against brain illness. (Source)


These trials show encouraging findings, particularly in terms of avoiding brain and cognitive disorders such as Alzheimer's disease.

Nevertheless, further research in humans is required before any conclusions can be drawn about its effectiveness.

Quercetin brain disease risk
Quercetin may prevent brain diseases such as Alzheimer's and dementia.

3) May Reduce Risk of Heart Disease

Worldwide, about 1 in 3 three people have elevated blood pressure.

Blood pressure that is too high can raise the chance of developing cardiovascular disease. (Source)

Heart disease is the leading cause of death in adults worldwide.

Quercetin may have the ability to lower blood pressure, thus lowering the risk of heart disease.

The antioxidant quercetin seems to have a calming impact on the blood vessels, according to research. (Source)

In one study, mice with high blood pressure were given quercetin twice a day for five weeks.

Each of their blood pressure readings dropped by about 18 percent, and their diastolic blood pressure reading declined by approximately 23 percent throughout the study period. (Source)

According to an analysis of nine human studies, consuming more than 500mg of quercetin per day may lower blood pressure.

When taken in doses more than 500mg, quercetin was shown to lower systolic blood pressure by about 2.6mm Hg and diastolic blood pressure by around 5.8mm Hg. (Source)


The results of this research are encouraging, but additional human trials are required before we can determine if quercetin is a feasible therapy or preventive strategy for high blood pressure and heart disease.

quercetin heart disease
Quercetin may reduce the risk of heart disease.

4) May Reduce Risk of Diabetes

Quercetin has been shown to lower blood sugar levels.

The presence of high blood sugar levels is associated with an increased risk of developing diabetes.

Several studies have been carried out on the effects of quercetin in animals suffering from type 2 diabetes. (Source)

Subjects who took quercetin had lower blood sugar levels than those who received a placebo, according to the study.

There was no noticeable variation in insulin sensitivity between the groups.

The antioxidant quercetin has been shown in human and animal studies to lower fasting blood sugar levels, thus protecting against diabetes. (Source, Source)


It has been demonstrated that quercetin may be effective in protecting against diabetes.

However, more human trials are required before quercetin may be considered an effective antidiabetic.

Quercetin diabetes
Quercetin may protect against diabetes.

5) Reduces Inflammation

Inflammation that persists for an extended period of time (chronic inflammation) may result in a variety of illnesses such as cancer, heart disease, diabetes, and others. (Source)

Free radicals not only cause cell damage, but they also activate genes that are involved in the process of inflammation.

As a result, elevated levels of free radicals in the body may result in an inflammatory response that is more severe than usual. (Source)

Quercetin seems to have anti-inflammatory properties, which may be related to its capacity to lower free radical levels, according to research.

Quercetin has been shown in test-tube experiments to decrease inflammatory markers in human cells, including tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). (Source)

According to a short, eight-week investigation on rheumatoid arthritis, individuals who took 500mg of quercetin every day had substantially less morning pain, morning stiffness, and after-activity discomfort than those who did not. (Source)

Those who took quercetin had lower levels of inflammatory indicators, such as tumour necrosis factor (TNF). (Source)


According to research, the antioxidant quercetin seems to have anti-inflammatory effects as well as antioxidant capabilities.

In contrast, further research is needed before any conclusions can be drawn.

quercetin inflammation
Quercetin seems to reduce inflammation.

6) Reduces Symptoms of Allergies

Quercetin has been shown to provide anti-allergy benefits and to alleviate allergy symptoms, most likely as a result of its anti-inflammatory properties.

According to research, quercetin may inhibit the activity of enzymes involved in inflammation as well as the production of substances that cause allergy symptoms, such as histamine. (Source, Source)

According to one study conducted on mice, supplementation with quercetin was shown to be effective in reducing anaphylactic responses. (Source)


Quercetin may have anti-allergy benefits, but additional human research are needed to determine whether or not it is a useful anti-allergy supplement.

quercetin allergies
Quercetin may reduce the symptoms of allergies.

7) Improves Exercise Performance

Quercetin has been shown to enhance physical performance and endurance.

When comparing the quercetin group to the control group, studies have shown that the VO2 max and endurance performance parameters increased substantially in the quercetin group. (Source)

According to an analysis of 11 human trials, quercetin supplementation may modestly enhance endurance exercise performance. (Source)

This supplement also has the ability to enhance muscle recovery after exercise.


Based on various research, quercetin may help you to run longer distances and improve endurance.

However, additional research in people is required before any conclusions can be drawn about its effectiveness.

quercetin exercise performance
Quercetin seems to be able to improve endurance exercise performance.

8) Helps Slow Ageing

Quercetin may have the ability to slow down the ageing process in some people.

It seems to have the ability to delay or reverse the ageing process in cells.

According to research, quercetin may aid in the restoration or elimination of ageing cells, as well as the reduction of ageing indicators. (Source, Source)

However, more human research is needed.


In cells, quercetin seems to slow the process of ageing, suggesting that it may be used as an anti-aging supplement. Though, additional study should be conducted before any conclusions are made.

quercetin anti ageing
Quercetin may be able to slow the ageing process.

Quercetins Side Effects & Interactions

Quercetin may be found in a variety of dietary sources.

Quercetin seems to be a safe supplement to use, with very minor adverse effects.

Taken in excess of 1,000mg of quercetin per day, some individuals may suffer minor adverse effects, such as those mentioned below, in which case they should stop taking quercetin and seek medical attention. (Source)

Quercetins Side Effects:

  • Headaches

  • Stomach Aches

  • Tingling Feeling

In addition, quercetin may worsen kidney problems; thus, if you have pre-existing kidney problems, avoid using quercetin. (Source)

It is important to note that quercetin may potentially stimulate tumour growth, particularly in cases of estrogen-dependent malignancy. (Source)

Additionally, owing to a lack of research in this area, you should avoid using quercetin supplements when pregnant or breastfeeding. (Source)

When ingested in foods, quercetin is completely safe for pregnant and nursing mothers.

Quercetin Interactions:

  • Antibiotics

  • Blood Pressure Medications

  • Drugs Affected By The Liver (P450 enzymes)

  • Drugs Affected By Pumps In Cells (P-Glycoprotein Substrates)

(Source, Source)


Quercetin appears to be relatively safe, with very few adverse effects. It may have an interaction with a variety of medicines.

However, since there have been just a few human trials, it is not recommended for pregnant or nursing women.

It should also be avoided by individuals who have estrogen-dependent breast cancer or pre-existing kidney issues.


Sources Of Quercetin

It is possible to find quercetin in a wide variety of commonly consumed fruits, vegetables, and other plant-based meals.

The quercetin concentration in these foods are often greater in the outer layers or in the peel. (Source)

Quercetin was discovered to be present in very high concentration in onions, which had about 300 mg per kilogram of weight, when compared to the other fruits and vegetables.

Food Sources Of Quercetin:

  • Capers

  • Yellow & Green Peppers

  • Red & White Onions

  • Cooked Asparagus

  • Red Leaf Lettuce

  • Broccoli

  • Shallots

  • Kale

  • Tomatoes

  • Cherries

  • Red Apples

  • Red Grapes

  • All Berries (blueberries, raspberries, cranberries etc.)

  • Green & Black Tea

  • Coffee

  • Red Wine


quercetin food sources
Quercetin is found in many common foods.

The antioxidant quercetin seems to be present in higher concentrations in organic tomatoes (up to 79% more) than in conventionally produced tomatoes, according to one research. (Source)

In other studies, however, researchers have discovered variations in the quercetin concentration of different tomato varieties, independent of the agricultural technique used.

There was also no change in quercetin content between organically produced bell peppers and conventionally grown bell peppers when comparing the two types of peppers studied. (Source)

The concentration of quercetin present in foods may vary depending on how the item was cultivated and processed.

However, there seems to be a contradiction of evidence in this area, indicating that more research is needed to determine if the technique of cultivating and producing quercetin has an effect on its concentration.

Quercetin may also be obtained as a dietary supplement.

It is available in both capsule and powder form, depending on your preference.


Quercetin Dosage

The optimal dose of quercetin is determined by a variety of variables, including the individual's age and health.

However, there hasn't been enough investigation done to determine a suitable dose of quercetin, and there isn't an established guideline for how much to take.

Despite this, quercetin was shown to be safe when taken at a dose of 500mg per day for up to 12 weeks. (Source)

When taken as a supplement, the most often dosage is 500 mg per day, although some individuals may tolerate up to 1,000 mg per day.

If you are thinking about taking quercetin, proceed with caution since there has been little study on the long-term or high-dose safety of quercetin.

Please keep in mind that supplements may also include other chemicals, such as vitamin C, bromelain and others flavonoids, which may aid the body's ability to absorb quercetin more readily but an increased dosage of these can result in certain side effects.

It is not always safe to use natural supplements, and various doses may have substantially varied effects on different people.

Consult with your pharmacist, physician, or other healthcare practitioner before taking this product.

Strictly avoid quercetin if you:

  • Have kidney issues.

  • Have estrogen-dependant breast cancer.

  • Are breastfeeding or pregnant.

  • Are taking antibiotics or blood pressure medication.

  • Are taking medicines that are affected by the liver.

Click here to read more about its side effects and interactions.


Summary of Quercetin

Quercetin seems to have a variety of beneficial effects.

It is a powerful antioxidant and anti-inflammatory molecule.

When taken in its natural form found in foods, quercetin appears to be relatively safe, with very minor adverse effects. 

It may, however, have certain interactions with specific medicines and illnesses in some cases.

Furthermore, there has been little long-term and high-dose safety studies.

All in all, quercetin seems to be a generally safe dietary supplement that has strong antioxidant and anti-inflammatory effects.

Quercetin seems to be a generally safe and useful supplement.

Synergistic Supplements

Quercetin has a number of synergistic effects with other substances.

Quercetin contains anti-inflammatory and antioxidant properties that are very effective.

Consequently, it is a good complement to the supplements listed below.

Top 4 Synergistic Supplements:

  1. Curcumin (Turmeric)

  2. Catechins (Green Tea)

  3. Resveratrol (Red Wine, Grapes etc.)

  4. Genistein (Soybeans)

Quercetin also has a low bioavailability, meaning the body does not well absorb it. (Source)

Some quercetin supplements may also include other ingredients, such as vitamin C or bromelain; their purpose is to improve absorption. (Source)


Frequently Asked Questions

Q: What are the health benefits of quercetin?

A: Quercetin is a powerful antioxidant and anti-inflammatory, it has various benefits such as reducing blood pressure and blood sugar levels. It may have anti-allergy and anticancer properties, and may reduce the risk of brain diseases.

Q: Who should not take quercetin?

A: You should avoid taking quercetin if you have kidney issues, or are a breastfeeding or pregnant woman. Also, those with estrogen-dependant cancer should strictly avoid quercetin.

Q: What are the side effects of quercetin?

A: Side effects from quercetin are mild and not very common, the reported side effects include; headache, stomach ache and tingling feelings. However, quercetin has interactions with some medications and diseases.

Q: Is quercetin the same as CoQ10?

A: No, CoQ10 and quercetin are not the same. CoQ10 is a type of enzyme and quercetin is a type of flavonoid. They have similar effects but are not the same.

You can find more articles about supplements here.

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