The origin of the onion is unknown but think it was from Asia. Sweet onions are available only in the summer months and cold climate varieties are all year long. The name onion comes from the Latin word unio which means one. The onion is named because it produces a single bulb unlike garlic. Onion bulbs may be red, white, or brown and the flavor is determined by the type. There are more than 1200 varieties of onions but they fall into two categories: spring-summer onions and cold climate storage onions. The onion has a long history dating back to ancient times. The Egyptians believed that its spherical shape and rings were a symbol of eternal life. In ancient Rome, gladiators massaged themselves with onions believing it firmed their muscles!
The shallot is a variety of onion that looks like garlic with small bulbs and tastes like an onion but is sweeter and milder in flavor. Shallots also tend to be more expensive than onions. They can be stored for at least 6 months. Also, the scallion, also known as the spring onion, salad onion, or green onion is another variety of onion. It has a hollow upper green portion and lacks a fully developed root bulb and it tastes milder than most onions.
Onions are a good source of vitamin C, B6, potassium, and manganese. Onions contain phytochemicals that have been the focus of many studies. These include a group of flavonoid compounds that function as antioxidants. Quercetin has been shown to be a powerful antioxidant and it is found in high levels in many onions. Shallots tend to contain the most flavonoids. A 2006 study in the American Journal of Clinical Nutrition showed that consumption of onions was associated with lower risks for head and neck cancers. as well as protection against cardiovascular disease and a lower risk for women developing osteoporosis.
In 1/2 cup of onions, there are 46 calories, 1.4 grams of protein, 10.7 grams of carbohydrates, and 1.5 grams of fiber.
Source: Reinhard, Tonia. Superfoods: the Healthiest Foods on the Planet. Buffalo, NY: Firefly, 2010. Print.