Potassium is important to every cell and tissue in your body. Its quality as an electrolyte means that it enables electrical signals to transmit across cells. This is critical for all muscle contraction, and especially so for the heart muscle. Without an electrical signal prompting the heart to contract, there would be no blood pumping through your body.
You can find potassium in meat, fish, dairy, vegetables and fruits -- bananas, for example, are an excellent source. Too little potassium in the body is a bad thing, but so is too much. Having too much (a condition known as hyperkalemia) is more of a concern as you age because kidney function decreases, meaning less potassium is removed from the body. Some good news? Studies indicate that consuming twice as much potassium as sodium -- regardless of the amounts of either -- improves heart health.