Onion, Herbaceous biennial plant (Allium cepa) of the family Alliaceae, probably native to southwestern Asia but now grown worldwide, and its edible bulb. Among the hardiest and oldest garden vegetable plants, onions bear a cluster of small, greenish white flowers on one or more leafless stalks.

Onions contain antioxidants and compounds that may reduce your risk of heart disease by fighting inflammation and lowering triglyceride and cholesterol levels. They contain a large amount of quercetin, a flavonoid antioxidant and anti-inflammatory that may help lower high blood pressure .