Mar 11 2010
What is quercetin and how important in the diet is it? – by Dr. Stohs
Quercetin is one of the most abundant flavonoids, occurring ubiquitously in fruits and vegetables. Flavonoids (both flavonols and flavanols) are naturally occurring plant pigments most commonly known for their antioxidant activity. Excellent sources include grapes, apples, cherries, berries, red onions, broccoli, capers (highest source), tea, citrus fruits and cocoa.
It forms the structural backbone for other naturally occurring chemicals as rutin, hesperidin, and naringenin. It is free of adverse effects at doses as high as 1700 mg/day in humans and at doses over 10X this high in experimental animals.
Quercetin is important in the diet and as a dietary supplement because of its excellent health benefits.
It is a potent antioxidant and may be the most potent flavonoid antioxidant. It exhibits a wide range of potentially beneficial effects and applications including: anti-inflammatory, antihypertensive, anti-proliferative, and immune system enhancing activities. For example, following quercetin administration plasma S-nitrophenols and nitrate as well as urinary nitrate concentrations increase, reliable measures of cardioprotective vasodilatory nitric oxide production. Another study demonstrated that after four weeks of quercetin administraton to human subjects, both systolic and diastolic bloods pressures significantly decreased, affirming its antihypertensive effects.
Research studies suggest that quercetin protects many organ systems including the heart, liver, nervous system, and gastrointestinal tract against oxidative stress, various disease states and diverse toxic chemicals. It prevents bone resorption, inhibits platelet aggregation, helps regulate blood sugar, and may support weight management. Some studies suggest that it may also support enhanced athletic performance. However, studies in human subjects indicate that it has no effect on total cholesterol, LDL cholesterol, or serum triglyceride (fat) levels.
The ability of quercetin to exhibit such a wide range of beneficial effects is related to its ability to exert multiple mechanisms of action. It is a potent scavenger of free radicals as superoxide anion and nitric oxide. It blocks the formation of the potent proxidant peroxynitrite, and blocks formation of DNA single strand breaks (DNA damage). Quercetin acts as a vasodilator by inhibiting a specific vasoconstrictor, thereby decreasing blood pressure. It promotes programmed cell death in various cancer cell lines, and thus may prevent the development of some forms of cancer. It also inhibits histamine release, thereby suppressing some allergic reactions.
Because of its numerous health benefits and diverse effects, quercetin is used in a number of AdvoCare products including Seasonal Support Capsules, Anti-Aging Formula Capsules, and BioCharge Powder in our BioTools.



statistics from the National Institutes of Health.