If there was a poster child for potassium, chances are the banana would be on the poster. The banana is an excellent source in a number of vitamins and minerals and potassium is quite possible the best mineral that comes from this tasty fruit. A medium sized banana contains more than 600 mg of potassium per serving, and for as little as 100 calories. One of the best ways to enjoy bananas is to add one to your morning smoothie to add flavor. In addition, you could enjoy a banana in between meals to help overeating at mealtime to help keep the calories down.