Quercetin is a pigment in many plants, fruits, and vegetables. Quercetin has powerful antioxidant properties and may help protect against certain health conditions, including heart disease.

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

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

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

Flavonoids are phytochemical compounds in plants, fruits, herbs, vegetables and nuts. Humans cannot make quercetin in their bodies, but many fruits, vegetables, and drinks contain it.

Foods and drinks that contain quercetin include:

  • broccoli
  • onions
  • peppers
  • buckwheat
  • capers
  • Brassica vegetables
  • apples
  • grapes
  • berries
  • tea
  • wine
  • many nuts and seeds

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

Possible health benefits of quercetin include:

1. Fighting free radicals

Quercetin has antioxidant properties.

Antioxidants help protect cells against oxidative damage. Oxidative damage occurs when an excess of free radicals in the body overwhelms the body’s antioxidant defenses. The medical term for this is oxidative stress.

Free radicals are unstable molecules in the body that can increase the risk of disease and quicken aging. The body produces free radicals through regular metabolic processes such as energy production.

However, different external factors can contribute to free radical production, including:

Quercetin is a more powerful antioxidant than vitamin C, 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 harm the body and contribute to specific health conditions. Quercetin can help inhibit inflammation in the body.

While consuming a diet high in quercetin-rich foods may help regulate inflammation, it is unclear whether taking high dose quercetin supplements is beneficial for reducing inflammatory markers

3. Reducing the risk of cancer

Research shows that a diet high in flavonoid-rich fruit and vegetables can lower the risk of certain cancers and slow cancer cell growth. However, more research is necessary to assess the direct links between quercetin intake and cancer risk.

4. Benefitting neurological health

Quercetin may reduce the risk of 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.

A 2021 study found that consuming quercetin-rich onion for 24 weeks reduces age-related cognitive decline. Animal studies have also shown quercetin to have a protective effect against cognitive impairment in Alzheimer’s disease.

However, research is ongoing, and doctors do not currently use quercetin to manage neurological disorders like Alzheimer’s.

5. Relieving allergy symptoms

Additional findings from Pharmacognosy Review suggest that quercetin might be an effective antihistamine, as it restricts histamine from being released from cells.

These anti-allergy properties indicate that quercetin may be a helpful supplement for those with allergic diseases, especially rhinitis. However, more research is needed to confirm this potential benefit. People with allergies should not supplement with quercetin unless directed to do so by their healthcare professional.

6. Antibacterial and antiviral effects

Quercetin has antibacterial and antiviral properties. Lab tests show that quercetin can inhibit the growth of many bacteria, including

Quercetin, along with other flavonoids, may help inhibit the growth of many viruses.

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 may help reduce the risk of these diseases.

Research suggests that quercetin may help protect heart health by mitigating blood vessel dysfunction mitigating endothelial dysfunction, and reducing heart disease risk factors like high blood pressure and atherosclerosis.

8. Lowering high blood pressure

According to a 2019 analysis, taking quercetin supplements could be an effective way to reduce blood pressure.

Further research shows 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 and reduced systolic blood pressure. Systolic blood pressure measures the pressure in the blood vessels during a heartbeat.

People can get quercetin through their diet by eating a range of fruit and vegetables daily.

Onions are amongst the richest sources of dietary flavonoids you can eat, providing 28.4–48.6 milligrams (mg) of quercetin per 100 g

Quercetin is available as a nutritional supplement, typically in doses of 500 to 1000 mg daily.

Supplements may also include other substances, such as bromelain or vitamin C, which may help the body absorb quercetin more effectively.

The natural antioxidants found in fruits and vegetables can be beneficial when consumed as part of a balanced and nutritious diet.

However, quercetin may interact with some medications, so people should ask their doctor before taking a supplement.

Quercetin is a flavonoid found in fruit and vegetables. It has a wide range of benefits, which people can get by including a variety of fruit and vegetables in their diet.

Although many studies have found several potential benefits of quercetin, many have been animal or in vitro studies.

Further research on humans is necessary to understand the benefits and side effects fully.

If people want to supplement their diet with quercetin, they should seek advice from a healthcare professional first.