Yams (Dioscorea) are a type of tuber vegetable that originated in Asia, Africa, and the Carribean  ,raw yam has the highest potassium levels amongst the 10 major staple foods of the world (see nutritional chart). Yam supplies 118 calories per 100 grams. Yam generally has a lower glycemic index, about 54% of glucose per 150 gram serving, compared to potato products,