Onions contain chromium, which assists in regulating blood sugar. For centuries, onions have been used to reduce inflammation and heal infections.
Raw onions are very low in calories, with only 40 calories per 100 grams (3.5 oz). By fresh weight, they are 89% water, 9% carbs and 1.7% fiber, with tiny amounts of protein and fat. The table below contains information on all the main nutrients in onions (1).
Protein: 1.1 g
Sugar: 4.2 g
Carbs: 9.3 g