The Folklore: Onions symbolized eternity to the ancient Egyptians, who buried the bulbs along with the Pharaohs. According to an old English rhyme, the thickness of an onion skin can predict the severity of winter’thin skins mean a mild winter; thick skins?watch out!
The Facts: Onions (Allium cepa) are loaded with phytonutrients. They are one of the richest sources of the flavonoid quercetin, a potent antioxidant thought to protect against heart disease, stroke and certain cancers. They also contain allium, the same phytonutrient plentiful in garlic. True to the color theory of nutrition?more color is better?more quercetin is found in red and yellow onions than in white.
Onions are a source of cancer-fighting lignans, as well as being rich in sulfur compounds, which are responsible for onions? pungent taste and smell. As for nutrients, onions provide small amounts of vitamin C, magnesium, potassium, folate and a decent amount of fiber.
Green or immature onions are often mistakenly called scallions, which technically are straight, with no bulb. They are similar nutritionally to other onions.
Green onions are the leading suspect in a recent large outbreak of hepatitis A?including three deaths?at a Pennsylvania restaurant. Green onions are notoriously difficult to clean, but it is imperative you wash them well and preferably also cook them.
The Findings: The tear-producing sulfur compounds in raw onions have a powerful blood-thinning effect, according to animal studies from the University of Wisconsin in Madison. Other research has linked sulfur compounds to lower blood pressure and cholesterol.
Even sweet varieties, like Vidalia and Walla Walla, provide phytonutrients, say scientists, who recently discovered they contain quercetin as well as myricetin and kaempferol, all antioxidants.
One of the newest areas of onion research deals with its potential as a probiotic. Onions contain fructooligosaccharides (FOS), nondigestible fiber that encourages the growth of friendly bacteria in the digestive tract. And, surprisingly, eating onions might actually help prevent stomach ulcers by scavenging free radicals and preventing growth of the ulcer-forming microbe H. pylori.
The Finer Points: Buy onions with closed ?necks? and dry, crackly skin that is firm all over, with no soft spots. Store onions in a cool, dry, dark, airy location?never in the refrigerator or under the sink, as they easily absorb moisture, which hastens spoilage.
To keep tears to a minimum when cutting onions, cut into the neck end first, leaving the root intact, as the root contains most of the odorous sulfur compounds. Alternatively, try chilling them before you slice or run the knife under water periodically. For the sweetest flavor, cook onions slowly over low to medium heat.