Onions are a staple in any well-stocked kitchen. Served raw, they add a crisp bite to salads and burgers, and when cooked they add a pungent, lightly spicy flavor that complements almost any savory dish--they can even be caramelized to sweetness! Onions are a member of the allium family of plants, which also includes garlic, leeks and chives. There are a wide variety of onions available, and each have slightly different flavors and uses in the kitchen. Yellow onions are your basic, everyday onion; they keep well and are very versatile. White onions have a very strong, robust flavor, and red onions are milder and slightly sweet. Shallots are a smaller variety of onion with a delicate, gourmet taste. Spring onions--also known as green onions or scallions--are very mild and are best served raw as a topping or garnish.
A well-balanced diet includes a wide variety of fruits and vegetables, and onions are one healthy vegetable! They are very low in calories (a 1/2 cup serving has only 30 calories), fat free, sodium free, and are high in vitamins C and B6. They also contain fiber, protein, iron and other essential nutrients.
Onions contain a compound called allyl propyl disulphide (also known as APDS) which is what gives them their pungent flavor and what makes you cry when you cut them. But this same compound also has blood sugar lowering effects. Allyl propyl disulphide competes with insulin in the liver, which triggers the body to produce more insulin, which helps transport glucose through the body and lowers blood sugar. Onions are also high in chromium, an essential mineral which helps cells respond to glucose.
Allyl propyl disulphide and onion's other sulfur compounds, as well as its chromium and vitamin B6 all contribute to improved cardiovascular health by lowering high blood pressure and high blood cholesterol levels, thereby cutting your risk of heart disease and stroke. Incorporate onions into your meals several times a week, raw, roasted, fried, caramelized or any other way you like them--so long as you stick to heart-healthy olive or canola oil when cooking them.
Onions contain high levels of quercetin and other flavanoids that have a host of health benefits. Flavanoids are antioxidants, which protect the body's cells from the damaging effects of free radicals. Quercetin has been shown to slow or even stop the growth of tumors and protect cells from cancer, particularly colon cancer. Quercetin, along with vitamin C, also provide onions with anti-inflammatory and antibacterial qualities, which can help reduce the pain and severity of arthritis, relieve upset stomachs and can help protect against respiratory infections, including the common cold.