Bananas are nutritious and an important source of instant energy, as well as providing vitamins and minerals. They are rich in fiber but low in fat. A single banana provides more than 100 calories. Bananas are a valuable source of dietary fiber, vitamins B6 and C, and the minerals magnesium and potassium, which help to fight disease. A banana contains about 420 mg of potassium, which is about 9% of the body’s daily requirement. Potassium is an essential mineral necessary to maintain blood sugar levels and for heart function. Foods that are made from bananas, such as banana chips, have higher micronutrient content but will contain saturated fats if they have been fried.