A new study has found that quercetin-rich onion skin extract has a positive effect on the blood pressure (BP) of people with hypertension.
In a randomised double-blind trial conducted by researchers from the University of Bonn in Germany, 68 overweight to obese patients with pre-hypertension and stage I hypertension were given either a quercetin-rich onion skin extract supplement (162mg per day) or a placebo for six weeks.
The study, published in the British Journal of Nutrition, found that those participants with hypertension who took the supplement experienced a positive effect on their BP compared to those taking the placebo. However, those who weren’t classed as having high blood pressure didn’t experience marked changes.
“In conclusion, supplementation with 162mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin,” wrote the authors.
However, the researchers remained unclear as to exactly how quercetin worked to reduce blood pressure. They also added: “We characterized the polyphenol spectrum of the extract, but we cannot exclude that other unknown components in the onion skin extract may have influenced our findings. Thus, strictly, the conclusion of our study is only true for quercetin-rich onion skin extract but not for pure quercetin.”