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

J Am Coll Nutr. 2013;32(3):160-4. doi: 10.1080/07315724.2013.797858.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adult
  • Antioxidants / administration & dosage
  • Cardiovascular Diseases / prevention & control
  • Cardiovascular System / drug effects
  • Cardiovascular System / metabolism
  • Endothelium, Vascular / drug effects*
  • Endothelium, Vascular / physiopathology
  • Fasting
  • Forearm / physiopathology
  • Humans
  • Male
  • Maltose / administration & dosage
  • Middle Aged
  • Onions / chemistry*
  • Plant Extracts / administration & dosage*
  • Postprandial Period / drug effects*
  • Quercetin / administration & dosage*
  • Vasodilation / drug effects


  • Antioxidants
  • Plant Extracts
  • Maltose
  • Quercetin