There are few meals that don’t start with the chopping of an onion. But this humble vegetable is more than just a tasty addition to food. Onions contain natural sugar, vitamins A, B6, C and E, folic acid, minerals such as iron, potassium and sodium and dietary fibre. They are an ancient folk remedy to relieve asthma, coughs, colds and congestion. Today, we know that some of the onion’s curative properties lie in a compound called allyl propyl disulphide, which helps to balance blood sugar levels.