Recently, potatoes have gotten a bad rap for being high in carbohydrates, but sweet potatoes' virtues outweigh their vices. Their flesh ranges from creamy white to the purple of some Japanese varieties to deep orange. Better yet, a medium-size sweet potato contains only about 140 calories yet still packs almost twice the recommended daily allowance of the antioxidant beta-carotene, a vitamin A precursor that gives the potatoes their rich color. Choose firm potatoes and store them in a cool, dark place to keep them from sprouting. For a wintertime snack, bake a few sweet potatoes and keep them in the refrigerator. When your sweet tooth hits, cut off a slice or two and enjoy a low-calorie, high-vitamin treat.