Onions are nutrient-dense, meaning they’re low in calories but high in vitamins and minerals. One medium onion has just 44 calories but delivers a considerable dose of vitamins, minerals and fiber. Vitamin C also acts as a powerful antioxidant in your body, protecting your cells against damage caused by unstable molecules called free radicals. Onions are also rich in B vitamins, including folate (B9) and pyridoxine (B6) — which play key roles in metabolism, red blood cell production and nerve function. This vegetable is particularly high in vitamin C, a nutrient involved in regulating immune health, collagen production, tissue repair and iron absorption.
