A new study, published in the Journal of Nutrition (November 2007, Volume 137, Pages 2405-2411) titled “Quercetin Reduces Blood Pressure in Hypertensive Subjects”, is said to be the first to report the blood pressure-lowering activity of this flavonol. The study found that a supplement of quercetin (naturally occurring component of onion) led to significant reductions in the blood pressure of 22 people with high blood pressure.
The randomised, double blind, placebo-controlled, crossover study, considered to be the gold-standard for experimental interventions, adds to an ever-growing body of reported health benefits for quercetin. The flavonol was previously linked to reduced risk of certain cancers. Building on science from animal studies reporting a potential hypotensive (blood pressure lowering) role for the flavonol, researchers from the University of Utah recruited 19 men and women with pre-hypertension (average BP 137/86 mmHg) and 22 hypertensives (average BP 148/96 mmHg). The subjects were randomly assigned to receive a daily supplement of quercetin or a placebo for 28 days. Lead author Randi Edwards and co-workers report that the hypertensives receiving the quercetin supplement experienced reductions in systolic and diastolic BP of 7 and 5 mmHg, respectively, compared to placebo. No BP changes were observed in the pre-hypertensives as a result of either intervention.
Specific whole foods of the allium family such as onions and garlic have a long history of being associated with cardiovascular benefits. This new evidence further clarifies one way onions support heart health by working to lower elevated blood pressure in people with high blood pressure.