Quercetin is a plant flavonol from the flavonoid group of polyphenols.
It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it.
It has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.
In a recent study from the University of Bonn, scientists found that extract from red onion skin could help reduce high blood pressure in overweight and obese people.
Previous studies found that quercetin may prevent heart disease due to its anti-hypertensive properties.
In the study, the team examined the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I high blood pressure.
A total of 70 participants were assigned to receive 162 mg/d quercetin from onion skin extract powder or placebo with 6-week treatment periods.
Before and after the intervention, ambulatory blood pressure (ABP) and office blood pressure were measured.
The team found that in the high blood pressure group, quercetin decreased 24 h systolic BP by -3·6 mmHg when compared with placebo.
In addition, quercetin strongly decreased daytime and night-time systolic BP in people with high blood pressure.
In the total group and also in the subgroup of hypertensives, blood pressure biomarkers, oxidation, inflammation, lipid, and glucose metabolism were not affected by quercetin.
The team concludes that supplementation with 162 mg/day of quercetin from onion skin extract lowers blood pressure.
These suggest a heart-protective effect of quercetin.
If you care about blood pressure, please read studies that black licorice could cause dangerous high blood pressure, and this common plant nutrient could help reduce high blood pressure.
For more information about nutrition, please see recent studies about how tea and coffee influence your risk of high blood pressure, and results showing this olive oil could reduce blood pressure in healthy people.
The research was published in the British Journal of Nutrition and conducted by Verena Brüll et al.
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