Onion

Onions not only provide flavor, they also provide important nutrients and health-promoting phytochemicals. Plenty of onion health research provides strong evidence of its nutritional value.

High in Vitamin C, onions are a good source of dietary fiber, and folic acid.
They also contain calcium, iron, and have a high protein quality (ratio of mg amino acid/gram protein).
Onions are low in sodium and contain no fat.
Onions contain quercetin, a flavonoid (one category of antioxidant compounds).
Onions contain organosulfur compounds that may offer unique health benefits.