One four-ounce tomato supplies about one-third of your daily need of vitamin C, plus a little beta carotene, potassium, folate and other B vitamins, iron, and fiber. Tomatoes are also rich in a carotenoid called lycopene, a potent antioxidant. The lycopene in cooked and processed tomatoes (sauce, paste, salsa, canned tomatoes) is more easily absorbed than that in raw tomatoes. Watermelon and pink grapefruit also contain lycopene.