It's necessary to keep a normal water balance between the cells and body fluids. It also plays an essential role in the response of nerves to stimulation and in the contraction of muscles.
Potassium also is necessary for cellular enzymes to work properly.
A potassium deficiency due to increased urinary loss often occurs when medication for certain heart diseases is used to prevent sodium and water retention. To overcome this loss, physicians often suggest eating more foods high in potassium. Additional potassium may be prescribed as a medicine. Foods high in potassium include bananas, cantaloupe, grapefruit, oranges, tomato or prune juice, honeydew melons, prunes, molasses and potatoes. Some foods high in potassium are also high in calories.