Potassium deficiency can be caused by lots of things. There are a lot of foods that can increase it, too! White potatoes w/ skin on, sweet potatoes, tomatoes, bananas, and oranges are all high in potassium. A baked potato w/ skin contains about 845 mg of potassium and a banana contains about 890mg. The requirement is 4700 mg/day, but very few of us meet that requirement due to our diets being low in fruits and veggies. Careful not to overdo it, though. You can get pretty sick if you get too much.