Page 1 of 3The idea that placing dishes of raw onions around the home would stave off illness dates back to the massive flu outbreak of 1919. The thinking went that halved onions could absorb germs. Even though that particular onion "fact" is merely a fiction, there are still plenty of good to recommend them: namely, great low-calorie flavor, plus a few legitimate health benefits to boot.
All about Alliums
You may think of onions as those white slices that come on your hamburger, but there's more to onions than you think. Onions are part of the Allium family, which includes a whole range of flavorful root vegetables: garlic; red, white and yellow onions; scallions (also called green or spring onions); shallots, leeks and chives. All alliums grow as underground bulbs with above-ground leaves and a flower stalk.
Onions contain beneficial polyphenols, sulfur compounds and vitamin C. The sulfur compounds produce their distinctive sharp odor and strong flavor, while also providing some health benefits because of their anti-clotting, antioxidant and anti-inflammatory properties. (Note that much of the research on the health benefits of alliums has focused on garlic, while onions are less thoroughly tested.)
These sulfur compounds are also responsible for making you "cry" when you slice an onion; when these compounds waft upward and mix with your natural tears, they form a mild (and irritating) sulfuric acid.
Nutrition by Variety
Did you know that the greatest nutritional value is contained in the outer rings of an onion? When you peel an onion, be sure to remove only the papery skin and any outer layer that's damaged—don't over peel!
All varieties of onions contain zero fat and cholesterol, and most have less than one gram of sodium, while they provide plenty of vitamins.
Red, white and yellow "cooking" or "storage" onions are widely available year-round; their papery skins help extend their shelf life. Red onions are typically stronger and more pungent. These onions are high in vitamin C.
Sweet onion varieties include Vidalia, Walla Walla and candy; these are mild and sweet-tasting, and are excellent in most recipes. They are also a good source of vitamin C and contain a small amount of calcium.
Leeks grow in upright cylinders instead of round bulbs; they're typically buried deep in sandy soil to produce a longer white portion. Leeks are commonly sautéed as a flavor base in soups and sauces. They pack quite a vitamin punch with high levels of vitamin C and A, plus calcium and iron.