Most onion cultivars are about 89% water, 4% sugar, 1% protein, 2% fibre, and 0.1% fat. Onions contain low amounts of essential nutrients (right table), are low in fats, and have an energy value of 166 kJ (40 kcal) per 100 g (3.5 oz). They contribute their flavor to savory dishes without raising caloric content appreciably.
Onions are cultivated and used around the world. As a food item, they are usually served cooked, as a vegetable or part of a prepared savory dish, but can also be eaten raw or used to make pickles or chutneys.