Onions are available in fresh, frozen, canned, pickled, and dehydrated forms. Onions can be used, usually chopped or sliced, in almost every type of food, including cooked foods and fresh salads, and as a spicy garnish; they are rarely eaten on their own but usually act as accompaniment to the main course. Depending on the variety, an onion can be sharp, spicy, tangy and pungent or mild and sweet.
Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom. Onions are a staple food in India, and are therefore fundamental to Indian cooking. They are commonly used as a base for curries, or made into a paste and eaten as a main course or as a side dish.
Evidence suggests that onions may be effective against the common cold, heart disease, diabetes, osteoporosis, and other diseases. They contain anti-inflammatory, anticholesterol, anticancer, and antioxidant components such as quercetin.
In many parts of the world, onions are used to heal blisters and boils. A traditional Maltese remedy for sea urchin wounds is to tie half a baked onion to the afflicted area overnight. In the morning, the spikes will be in the onion. In the United States, products that contain onion extract (such as Mederma) are used in the treatment of topical scars, though studies have found no evidence that they are effective.
Onions, like garlic, are members of the Allium family, and both are rich in powerful sulfur-containing compounds that are responsible for their pungent odors and for many of their health-promoting effects. Onions contain allyl propyl disulphide, while garlic is rich in allicin, diallyl disulphide, diallyl trisulfide and others. In addition, onions are very rich in chromium, a trace mineral that helps cells respond to insulin, plus vitamin C, and numerous flavonoids, most notably, quercetin.
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