1.Vitamin C
All kinds are considered a good source of this nutrient. Vitamin C helps your body heal and form blood vessels and other parts of the body. It’s also an antioxidant that fights free radicals. Those are molecules your body makes that can sometimes trigger damage. Experts recommend 90 milligrams of vitamin C a day. That’s the Daily Value, or the amount of a nutrient you should try to get every day. One average-sized onion has 9% to 18% of your Daily Value.
2.Fiber
Onions have two kinds of fiber: dietary and prebiotic. One cup has 12% of the 21-38 grams you need every day. Fiber helps you feel full longer and have regular bowel movements. And when you feel full, you’re less likely to eat as much. That helps lower your risk of obesity. The prebiotic fiber in onions feeds your gut bacteria (probiotics) so they can grow.