Apples contain powerful antioxidants and nutrients that fight off disease and boosts your immune system. Quercetin, a phytochemical that contains cancer-fighting antioxidants and anti-inflammatory properties, is found in apples. Apples contain more free phenolics than any other common fruit, and there are few fruits with as many antioxidants. Vitamin C plays a variety of roles when it comes to maintaining a healthy immune system. When you eat one large apple, you get approximately 10.3mg of vitamin C, which is around 12% of your daily recommended intake. The amount of antioxidants that you get in one apple is equal to an impressive 1,500 milligrams of Vitamin C.