Bananas Lower Heart RateBananas are an excellent source of potassium and potassium is needed to maintain a low heart rate, states the University of Maryland Medical Center. Symptoms of low potassium include muscle cramps and lack of energy, which can lead to an irregular heartbeat. Bananas contain 400 mg of potassium in 96 calories. This is 11 percent of the daily requirement. Bananas have less than 1 mg of sodium, which makes them a valuable food for people on reduced sodium diets as well.