The deep orange-yellow color of sweet potatoes tells you that they're high in the antioxidant beta carotene. Food sources of beta carotene, which is converted to vitamin A in your body, may help slow the aging process and reduce the risk of some cancers. In addition to being an excellent source of vitamins A and C, sweet potatoes are a good source of fiber, vitamin B-6 and potassium. And like all vegetables, they're fat-free and relatively low in calories — one-half of a large sweet potato has just 81 calories.