Chronic intake of onion extract containing quercetin improved postprandial endothelial dysfunction in healthy men.

BACKGROUND

Epidemiologic studies have shown that dietary flavonoids reduce the risk of cardiovascular events. Onion is rich in quercetin, a strong antioxidant flavonoid. In some in vitro studies, quercetin improved endothelial function associated with atherosclerosis, a leading cause of cardiovascular events.

OBJECTIVE

The aim of this study was to determine whether chronic onion extract intake would improve postprandial endothelial dysfunction induced by an oral maltose load in healthy men.

METHODS

Healthy men (44±10 years, n=23) received 4.3 g of onion extract (containing 51 mg of quercetin) once a day for 30 days. Before and after the chronic onion extract intake, fasting and postprandial flow-mediated vasodilation (FMD) responses were measured.

RESULTS

Maltose loading significantly decreased FMD both before and after chronic onion extract intake (p=0.000037 and p=0.0035, respectively). The chronic onion extract intake did not significantly affect fasting FMD (p=0.069) but improved the postprandial FMD significantly from 5.1%±2.2% to 6.7%±2.6% (p=0.00015). The chronic onion extract intake did not alter systemic and forearm hemodynamics.

CONCLUSION

These findings suggest that chronic onion extract intake ameliorates postprandial endothelial dysfunction in healthy men and may be beneficial for improving cardiovascular health.