Quercetin is a flavonoid widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest). Foods containing quercetin include brewed, black or green tea, apples,sweet potato, watercress, red onion, broccoli, black plums and a number of berries, including cultivated blueberry, bilberry, lingonberry, cranberry, chokeberry, rowanberry and the fruit of the prickly pearcactus.
In a trial quercetin supplementation reduced systolic blood pressure and blood levels of oxLDL in 93 overweight subjects with a high-cardiovascular disease risk. Quercetin supplementation led to decreased systolic blood pressure by 2.6 mmHg in the entire study group, by 2.9 mmHg in the subgroup of hypertensive subjects and by 3.7 mmHg in the subgroup of younger adults aged 25-50 years. Quercetin significantly decreased plasma concentrations of atherogenic oxLDL, but did not affect inflammatory markers. Blood parameters of liver and kidney function, haematology and serum electrolytes did not reveal any adverse effects of quercetin. (1, 2). Remarkably Quercetin does not increase the body’s own antioxidant Uric Acid. A recent trial showed that a combination of quercetin, vitamin C, and niacin supplements did not show strong changes in cardiovascular risk factors in 1002 healthy volunteers, except form small reductions in blood pressure and cholesterol (3). This indicates that quercetine is more effective in subjects at high risk of cardiovascular disease. Unfortunately the blood pressure lowering effects were reduced upon aging, suggesting that quercetin does not help in reducing age related increases in blood pressure.
Thus far insufficient evidence for beneficial effects of quercetin on reduction of cardiovascular disease risk are available. It is likely that quercetin consumption contributes to overall health. However, this limited evidence does not yet warrant daily quercetin supplementation.
Accepted EFSA Claims
- No health claims have been authorized by the European Food Safety Authorisation
- Egert S et al., Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebo-controlled cross-over study. The British journal of nutrition 102, 1065-74 (Oct, 2009).
- Egert S et al., Daily quercetin supplementation dose-dependently increases plasma quercetin concentrations in healthy humans. The Journal of nutrition 138, 1615-21 (Sep, 2008).
- Knab AM et al., Influence of quercetin supplementation on disease risk factors in community-dwelling adults. Journal of the American Dietetic Association 111, 542-9 (Apr, 2011).