Quercetin Background and Benefits
Quercetin is the common name for the chemical formally known as 3,3',4',5,7-pentahydroxy-2-phenylchromen-4-one. It is a flavonol, which is a type of polyphenol that plants often use as pigments. Quercetin is found widely in nature and in many fruits, vegetables, leaves, seeds, and grains that are commonly consumed. Capers, red onions, and kale in particular contain substantial amounts of quercetin. Honey may also contain quercetin, depending on its plant source.
Oak trees also synthesise high levels of quercetin, and indeed the name quercetin comes from the word quercetum, meaning oak forest, after the oak genusQuercus. Quercetin is a common ingredient in beverages, foods and health supplements.
Quercetin has been the subject of much research over the years. Due to its antioxidant and anti-inflammatory properties, it appears to have a wide range of health benefits. For example, research shows that quercetin may support improved comfort and reduced inflammation in those suffering rheumatoid arthritis.
Quercetin has been widely studied for its benefits for prostate health. In studies on cells - called in vitro studies, quercetin indirectly blocks the activity of two genes that are known to cause prostate problems, namely androgen receptor and prostate-specific antigen. Quercetin also shows great promise in inducing apoptosis - also known as programmed cell death - in prostate cancer cell lines - without affecting healthy prostate cells.
Quercetin also provides immune support and has been researched for its role as an "ionophore" for zinc. As an ionophore, quercetin acts like a carrier to get certain molecules, such as zinc, across cell membranes. By helping to increase the concentration of zinc inside cells, quercetin may assist in reducing the severity and duration of upper respiratory infections.
One of quercetin's most well-known benefits is that it supports healthy blood pressure. Researchers undertook a systematic review of all the clinical trials looking at the effect of quercetin on blood pressure. By doing this, they were able to determine which studies were high quality. Once they had selected those high-quality studies, they were then able to pool the data - this is known as a meta-analysis. This approach provides a much stronger basis for working out whether an ingredient does or doesn't work, compared to looking at one or two clinical studies in isolation.
The systematic review and meta-analysis pooled the results from seven clinical trials with a total of 587 participants. It showed that taking at least 500mg quercetin daily resulted in a statistically significant reduction in blood pressure. The mechanism of action of quercetin for healthy blood flow is not fully understood but is thought to include a combination of vasorelaxation (relaxation of vascular tension) and antioxidant effects.
Uses of Quercetin
One of the most common reasons for taking quercetin is to support a healthy immune system. It is also used to support heart functions, including supporting healthy blood flow and exercise recovery. Quercetin is also used to support a healthy prostate, especially in men over the age of 50.
Heart health support
Some research indicates that quercetin can help support heart health in elderly men. This research studied dietary sources of quercetin such as apples, onions and tea.
Early research indicates that quercetin may help you to recover from intense aerobic exercise more quickly.
Support healthy circulation
Quercetin may be able to help support healthy circulation, especially in mild cases of occasional elevated blood pressure.
Prostate health support
Oral supplements of quercetin may be able to manage discomfort and swelling of the prostate gland. These conditions often occur in men as they age, especially after 50 years.
Signs You May Need Quercetin
Swelling and discomfort of the prostate gland is one of the most significant signs that you may need quercetin supplements. Cardiovascular conditions such as an unhealthy cholesterol profile and poor circulation may indicate that quercetin may benefit you. Endurance athletes who want to improve their recovery after a workout may also need to use quercetin. Additional signs that may mean you could benefit from quercetin include chronic fatigue and seasonal conditions.
Ghafouri-Fard S, Shabestari FA, Vaezi S, Abak A, Shoorei H, Karimi A, Taheri M, Basiri A. Emerging impact of quercetin in the treatment of prostate cancer. Biomed Pharmacother. 2021 Jun;138:111548. doi: 10.1016/j.biopha.2021.111548. Epub 2021 Apr 1. PMID: 34311541.
Javadi F, Ahmadzadeh A, Eghtesadi S, Aryaeian N, Zabihiyeganeh M, Rahimi Foroushani A, Jazayeri S. The Effect of Quercetin on Inflammatory Factors and Clinical Symptoms in Women with Rheumatoid Arthritis: A Double-Blind, Randomized Controlled Trial. J Am Coll Nutr. 2017 Jan;36(1):9-15. doi: 10.1080/07315724.2016.1140093. Epub 2016 Oct 6. PMID: 27710596.
Serban MC, Sahebkar A, Zanchetti A, Mikhailidis DP, Howard G, Antal D, Andrica F, Ahmed A, Aronow WS, Muntner P, Lip GY, Graham I, Wong N, Rysz J, Banach M. Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Am Heart Assoc. 2016 Jul 12;5(7):e002713. doi: 10.1161/JAHA.115.002713. PMID: 27405810; PMCID: PMC5015358.