Joanna Blythman and Rosie Sykes, guardian.co.uk, Updated: October 28, 2013 11:22 IST
Healthy eating needn't make you weep - this most basic veg is a secret nutritional superstar
As winter sets in, and this year's UK crop, now dried off, comes on to the market, the comforting warmth of the humble onion really comes into its own. Though they can be unsubtle, mouth-mugging bulbs when served raw, when gently sweated to fondant softness, onions bring a silky savoury sweetness to a piping bowl of soup or a gutsy cold-weather stew. A classic French tarte à l'oignon will easily absorb a melting, translucent kilo. Patience is required, however; undercooked onions that haven't quite surrendered their crunch are horrible. But fried crisply to a rich amber colour, onions transform potentially dull bowls of lentils into an enticing Indian tarka dhal or Middle Eastern mejadra.
Why are onions good for me?
Onions are particularly rich sources of sulphur compounds (these are
also what give them their pungency and stingingly eye-watering capacity)
and antioxidant flavonoids, such as quercetin, which protects us against cell damage. Fiddly though it is, try to peel off the paper skin only when preparing, as these flavonoids are most concentrated in the outer layers of the onion. Some research suggests that quercetin's anti-histamine effect can help ease symptoms of asthma and allergies. Onions are also one of the richest sources of chromium, a metal which increases the action of insulin, and may therefore help control blood sugar levels. High blood sugar levels can ultimately lead to complications including heart disease.
Where to buy and what to pay
Onion prices vary widely. Usually loose ones (guide price 75p-£1 a kilo) are cheaper than packs, but not always, so check what you're actually paying. Large onions, sold singly, or in packs, always carry a significant premium, as do insipid varieties marketed as mild.
Joanna Blythman is the author of What To Eat (Fourth Estate, £9.99). To order a copy for £7.99 with free UK p&p, go to guardianbookshop.co.uk