Toss a half-cup of these peppers into your next stir-fry or salad and you’ll score nearly half of the vitamin C you need in a day. Like other antioxidants, the nutrient protects against skin-damaging free radicals. The body also uses vitamin C to produce collagen, the protein that gives skin its firmness. Don’t like peppers? Opt for other C-rich foods, like papayas, strawberries, kiwi, and kale.