Wham: Compound in Onions Found to Aid in Lowering High Blood Pressure

A ndew study shows that Quercitin, the compound most commonly associated with onions, may reduce blood pressure by an average of five millimitres of mercury.

This flavonol has not been studied for its anti-hypertension effects in the past; this group found a daily 730 milligram supplement of quercitin led to significant reductions in the blood pressure of 22 people with high blood pressure. While this is considered a smaller, "pilot" scale trial, the news is good because this is just another benefit for a flavonol that has already been discovered to be extremely valuable in human consumption.

Hypertension is defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, affects about 600 million people worldwide and is associated with over seven million deaths. In the USA, the hypertension numbers have recently been adjusted. A person can be considered to be in "pre-hypertension" today with numbers that were considered normal just a few years ago.

The randomized, double-blind, placebo-controlled, crossover study, (the best way to manage experimental trials) adds to an ever-growing body of reported health benefits for quercitin. 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 (730 mg) or placebo for 28 days.

Lead author Randi Edwards and co-workers report that the hypertensives receiving the quercitin supplement experienced reductions in systolic and diastolic BP of seven and five mmHg, respectively, compared to placebo.

It is important to note that no BP changes were observed in the pre-hypertensives as a result of these interventions.

"These data are the first to our knowledge to show that quercetin supplementation reduces blood pressure in hypertensive subjects," stated the researchers.

Although no mechanism of action study was performed by the researchers, they suggested that the flavonoid could limit the production of angiotensin II, a molecule that constricts blood vessels (vasoconstrictor) leading to an increase in blood pressure. Further investigation would be required to confirm this speculation.

Dave