10 Health Benefits of Onion The onion may not be everyone’s favorite vegetable, but it sure is beneficial. The next time you peel onions and start crying, just think of all the great health benefits you are getting. They contain lots of fiber and antioxidants. They are also rich in vitamins B and C, and are full of sulphur, iron, potassium, phosphorous, calcium, and manganese. Each 100 grams of onion contains about 45 calories. The humble onion is found in every kitchen, but its curative powers ma