Potassium is key for maintaining proper nerve and muscle function and helps your cells maintain proper fluid levels. Adults need about 3500mg of potassium daily. However, since potassium overdose can be a problem, it is not recommended that you take potassium supplements. Where can you get potassium? Bananas are a potassium powerhouse, containing about 700 mg of potassium each, but plenty of other foods provide it as well. The following foods each contain more than 350mg of potassium each.