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It 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. What is quercetin Share on PinterestCameron Whitman/StocksyQuercetin 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:broccolionionspeppersbuckwheatcapersBrassica vegetablesapplesgrapesberriesteawinemany nuts and seeds Quercetin is one of the most common and well-researched flavonoids. 8 benefits of quercetin Possible health benefits of quercetin include:fighting free radicalsreducing inflammationreducing cancer riskreducing the risk of neurological diseasesrelieving allergiesreducing the risk of infectionsreducing the risk of heart diseaselowering blood pressure 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:pollutioncigarette smokeradiationsun exposurestressalcohol consumptionchemical toxinsgreenhouse gases 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 Salmonella enteritidisStaphylococcus aureusEscherichia coliProteusAspergillus flavus 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. Dosage 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. Side effects and risks 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. Summary 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. Last medically reviewed on July 5, 2022Cancer / OncologyNeurology / NeuroscienceNutrition / DietComplementary Medicine / Alternative Medicine 20 sourcescollapsedMedical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.Agrawal, P. K., et al. (2020). Quercetin: Antiviral significance and possible COVID-19 integrative considerations.https://journals.sagepub.com/doi/full/10.1177/1934578X20976293Dagher, O., et al. (2021). Therapeutic potential of quercetin to alleviate endothelial dysfunction in age-related cardiovascular diseases.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8042157/David, A. V. A., et al. (2016). Overviews of biological importance of quercetin: A bioactive flavonoid.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5214562/Dehghani, F., et al. (2020). Effects of quercetin supplementation on inflammatory factors and quality of life in post-myocardial infarction patients: A double blind, placebo-controlled, randomized clinical trial [abstract].https://pubmed.ncbi.nlm.nih.gov/33216421/De Patrillo, A. et al. (2021). Quercetin and its derivates as antiviral potentials: A comprehensive review.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8662201/Li, Y., et al. (2016). Quercetin, inflammation and immunity.https://www.mdpi.com/2072-6643/8/3/167/htmMohos, V., et al. (2021). Inhibitory effects of quercetin and its main methyl, sulfate, and glucuronic acid conjugates on cytochrome P450 enzymes, and on OATP, BCRP and MRP2 transporters.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468908/Nishihira, J., et al. (2021). The effect of 24-week continuous intake of quercetin-rich onion on age-related cognitive decline in healthy elderly people: a randomized, double-blind, placebo-controlled, parallel-group comparative clinical trial.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8482389/Nishimura, M., et al. (2020). Effect of daily ingestion of quercetin-rich onion powder for 12 weeks on visceral fat: A randomised, double-blind, placebo-controlled, parallel-groupstudy.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7019606/Ozgen, S., et al. (2016). Antioxidant activity of quercetin: A mechanistic review.https://www.researchgate.net/publication/311773564_Antioxidant_Activity_of_Quercetin_A_Mechanistic_ReviewPanche, A. N., et al. (2016). Flavonoids: An overview.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5465813/Rather, R. A., et al (2019). Quercetin as an innovative therapeutic tool for cancer chemoprevention: Molecular mechanisms and implications in human health.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7774748/Quercetin. (2020).https://www.ncbi.nlm.nih.gov/books/NBK556474/Saeedi-boroujeni, A., et al. (2021). Anti-inflammatory potential of Quercetin in COVID-19 treatment.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840793/Selamoglu, Z. (2016). Antioxidant activity of quercetin: A mechanistic review.https://www.researchgate.net/publication/311773564_Antioxidant_Activity_of_Quercetin_A_Mechanistic_ReviewSerban, M. C., et al. (2016). Effects of quercetin on blood pressure: A systematic review and meta‐analysis of randomized controlled trials.https://www.ahajournals.org/doi/pdf/10.1161/JAHA.115.002713Tamtaji, O. R., et al. (2019). The effects of quercetin supplementation on blood pressures and endothelial function among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials [abstract].https://pubmed.ncbi.nlm.nih.gov/31092175/Ullah, A., et al. (2020). Important flavonoids and their role as a therapeutic agent.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697716/Yang, D., et al. (2020). Quercetin: It's main pharmacological activity and potential application in clinical medicine.https://www.hindawi.com/journals/omcl/2020/8825387/Zhang, X.-W., et al. (2020). Quercetin in animal models of alzheimer's disease: A systematic review of preclinical studies.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7014205/FEEDBACK:Medically reviewed by Jillian Kubala, MS, RD, Nutrition — By Beth Sissons and Tom Rush — Updated on July 5, 2022 Latest newsWhat sets 'SuperAgers' apart? 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