Foods that commonly contain quercetin include onions, apples, grapes, berries, broccoli, citrus fruits, cherries, green tea, coffee, red wine, and capers

Quercetin is a pigment that adds color to many fruits and vegetables. It’s found mainly in the skins and leaves of plants. Light stimulates the production of quercetin, so an apple at the top of a tree may have more quercetin than one that doesn't get direct sunlight.

Quercetin may be referred to as a phytochemical, polyphenol, or flavonoid. Phytochemicals are substances produced by plants that may have health benefits for humans. Polyphenols and flavonoids are types of phytochemicals.

Quercetin is a powerful antioxidant. Antioxidants help fight free radicals, which are molecules that contain unpaired electrons. Because electrons naturally want to pair up, free radicals roam around the body, pulling electrons away from other molecules. This process can damage cells and DNA. Quercetin "cleans up" free radicals by pairing with their single electrons so they can no longer cause damage.

Dietary intakes of quercetin in the U.S. have been reported to be around 6-18 milligrams (mg) per day. However, if you’re eating several servings of fruits and vegetables on a daily basis, you’re likely consuming much more quercetin.

Why You Need Quercetin

Research shows that quercetin has many health benefits, including:

Heart Health

Quercetin has been shown to support the cardiovascular system by lowering blood pressure and cholesterol and relaxing blood vessels. Because reduced blood flow can cause erectile dysfunction, flavonoids like quercetin can also improve men's sexual health.

Brain Health

Improved circulation improves brain health as well. But quercetin can protect the brain in other ways, too. It may reduce inflammation and protect brain cells from toxins. Its antioxidant powers could lower the risk of Alzheimer's disease and other degenerative diseases of the brain.

Anti-Cancer Effects

When free radicals damage cells in the body, those cells sometimes develop into cancer. Quercetin and other antioxidants reduce the risk of cancer by combating free radicals. A few studies have targeted quercetin particularly. In one, it slowed tumor growth. In another, it lowered the risk of lung cancer. The third was a lab study, which found that quercetin had the ability to attack leukemia cells.

Therapeutic potential of quercetin as a cardiovascular agent

Rahul V Patel 1, Bhupendra M Mistry 2, Surendra K Shinde 3, Riyaz Syed 4, Vijay Singh 5, Han-Seung Shin 6

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Flavonoids are integral components of various vegetation and in foods; consequently, they represent an inevitable part of the diet. Historical and epidemiological proof recommend that diet plans consisting of flavonoids such as quercetin have positive health benefits, especially on the heart. Flavonoids have been proven to be active against hypertension, inflammation, diabetes and vascular diseases. Quercetin exhibits significant heart related benefits as inhibition of LDL oxidation, endothelium-independent vasodilator effects, reduction of adhesion molecules and other inflammatory markers, the protective effect on nitric oxide and endothelial function under conditions of oxidative stress, prevention of neuronal oxidative and inflammatory damage and platelet antiaggregant effects. Searching for experimental evidence to validate the cardioprotective effects of quercetin, we review here the recent detailed in vivo studies. Quercetin and its derivatives lead to an enhancement in heart features, indicating the prospective for quercetin to be used therapeutically in the treatment of cardiac diseases. Several evidence-based studies suggest mechanisms to observe cardiovascular diseases such as aging effects, hypertension, angiotensin-converting enzyme activity and endothelial-dependent and independent functions. Different animal models including human are also used to elucidate the in vivo role of quercetin in cardiovascular diseases. The role of quercetin and its derivatives may go beyond their existence in food and has potential as a lead molecule in drug development programs.

Keywords: Bioassay; Cardiovascular action; Flavonoids; Plant-derived polyphenol; Quercetin.

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