Fasting-Caloric Restriction

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.