This article details the possible benefits of quercetin. It also looks at the potential side effects.

People can get quercetin through a balanced diet or by taking a supplement.

Quercetin is a pigment found in many plants, fruits, and vegetables. It may have some health benefits and help prevent a range of conditions.

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Quercetin is one of the most common and well-researched flavonoids.

Quercetin is also present in herbal remedies, such as ginkgo biloba and St John’s wort. People can also take quercetin as a supplement.

Humans cannot make quercetin in their body, but many fruits, vegetables, and drinks contain it.

Flavonoids are a particular chemical in plants, called phytonutrients, and have a wide range of health benefits.

Quercetin is a flavonol, which is a sub-category of flavonoids.

Possible health benefits of quercetin include:

1. Fighting free radicals

Quercetin has antioxidant properties.

Antioxidants work to protect the body from free radicals. Free radicals are unstable molecules in the body that can increase the risk of disease and quicken aging.

Many different factors can contribute to more free radicals, including:

pollution

cigarette smoke

radiation

chemical toxins

greenhouse gases

Quercetin is a more powerful antioxidant than vitamin C, vitamin E, or beta carotene.

2. Reducing inflammation

Inflammation is the body’s natural response to stress and injuries and usually helps the body heal. However, chronic inflammation can be harmful to the body and may contribute to certain health conditions.

However, quercetin might help reduce inflammation. One study on animals found that quercetin prevented both acute and chronic inflammation, in addition to showing anti-arthritis properties.

Results from human studies have provided mixed results, however. While research on healthy male athletes found that quercetin could reduce inflammation, it did not have the same effect in women with rheumatoid arthritis.

3. Reducing the risk of cancer

Share on Pinterest Quercetin occurs naturally in onions.

Quercetin may contain anticancer properties that might help prevent the spread of cancerous cells and tumor growth.

Research has shown that a diet high in flavonoids, such as quercetin, can help prevent cancers. Fruits and vegetables are full of flavonoids, so increasing intake of these foods might reduce the risk of many types of cancer.

A 2015 report found that quercetin restricted the growth of prostate cancer cells in mice and rats.

A 2018 in vitro study indicated that quercetin showed promise in both the treatment and prevention of prostate cancer. In vitro means the researchers performed the experiment outside of a living thing, for example, in a test tube.

Researchers still need to find out more about the anticancer properties of quercetin in humans and to ensure the body can absorb high doses of quercetin effectively.

4. Preventing neurological diseases

Quercetin may help to prevent neurodegenerative diseases, such as Alzheimer’s or Parkinson’s disease.

Oxidative stress contributes to the development of neurodegenerative diseases. Oxidative stress occurs when there is an imbalance of free radicals in the body. The antioxidant properties of quercetin may help fight free radicals.

Research on rats showed that quercetin could protect against oxidative stress. It also showed quercetin could protect against the toxic effect of certain metals on the nervous system.

5. Relieving allergy symptoms

Research suggests that quercetin might be an effective antihistamine, as it restricts histamine from being released from cells.

These anti-allergy properties indicate that quercetin might help treat bronchitis and asthma.

6. Preventing infections

Quercetin has antibacterial properties, which are effective against almost all types of bacteria, particularly those linked to:

stomach and intestines

skin

respiratory

urinary

Quercetin, along with other flavonoids, might help fight off viruses, such as:

7. Reducing the risk of heart disease

Diet plays an essential role in reducing the risk of cardiovascular diseases, such as heart disease and strokes. Because fruit and vegetables contain flavonoids, eating more of them can reduce the risk of these diseases.

Quercetin may improve blood vessel cell health and blood flow through arteries in people with heart disease.

8. Lowering high blood pressure

According to a 2016 study by the American Heart and Stroke Association, taking quercetin supplements could be an effective way to reduce blood pressure.

Other research showed that people who were overweight and took a quercetin supplement of 150 milligrams (mg) per day had lower levels of harmful cholesterol in their blood, as well as reduced systolic blood pressure, which measures the pressure in the blood vessels during a heartbeat.