While still not well-known as a superfood, onions are among the oldest and most widely cultivated plants in the world. Onions are just one species within the genus Allium, which includes garlic, leeks, chives and shallots. Up to 4,000 years ago, ancient medical texts from Egypt, Greece, Rome, China and India cited the thera- peutic applications of Allium vegetables. To this day, the humble onion remains a staple in almost every major cuisine.

The Benefits

• QUALITY QUERCETIN: Onions contain some of the highest concentrations of quercetin, a type of flavonoid with antioxidant properties. Studies suggest that this bio­ active substance may be beneficial against a variety of diseases, includ­ ing cardiovascular disease, diabetes, cancer and asthma. A study by the University of Guelph found that red onions grown in Ontario boast some of the highest levels of quer­ cetin compared with onions grown in other parts of the world. Onion skins contain the highest amount of this potent antioxidant, so peel­ ing may significantly reduce its quantity. Try throwing quartered onions with the skin on into your stock, or bake them in their skins to savour all that goodness.
• SUPER SULPHUR: Organosul­phur compounds are largely respon­sible for the strong taste and smell of Allium vegetables. When cut, onions produce a sulphur­based gas that reacts with the water in your eyes to form sulphuric acid, causing tears. Sulphur is essential for all life—it’s one of the most common minerals in the human body, as well as the fifth most common element on Earth. Organosulphur compounds are associated with strong anti­ carcinogenic properties because of their role in activating several enzymes that detoxify potentially cancer­causing substances. Unlike quercetin, the sulphur compounds of onions are richest in the fleshy layers, and many of their health benefits are available only once the onion tissues are chopped.
• SKIN DEEP: Onions can also be applied topically. Studies show that onion extract applied to the skin may improve the appearance of scars and stretch marks. Onion juice is reported to be an effective topical therapy for alopecia areata (hair loss). Keratin, a protein that helps make up strong hair, is sulphur­rich, too, so applying onions to the hair and scalp may add to the support of strong tresses, pre­ vent hair loss and promote growth. Onions have long been used in tradi­tional medicine for their antimicrobial properties—sulphur, for instance, is known to inhibit the growth of many microorganisms. Medicated shampoos often contain sulphur, which helps to slow down dandruff buildup and remove flakes. Trendsetting K­beauty companies are in the know about the benefits of onions, so keep your eyes peeled for skin­care products formulated with this superfood.

Try this superfood in our Baked Cousous-Stuffed Onions.