Sweet potatoes of all varieties are high in vitamin A, vitamin C and manganese. They are also a good source of copper, dietary fiber, vitamin B6, potassium and iron. Sweet potatoes are known to improve blood sugar regulation and some studies have discovered significant antibacterial and antifungal properties. The primary nutritional benefit, and the one for which Okinawan sweet potatoes are especially prized, is their high antioxidant levels.4 The antioxidant known as anthocyanin is the pigment which is responsible for the brilliant purple color of the flesh. It is the same pigment that gives blueberries, red grapes and red cabbage their color.