Potassium

Fresh lettuce juice also contains potassium. As an electrolyte, potassium helps the fluids in your body conduct energy. This proves essential to nerve and muscle function, because nerve communication whether that communication occurs between two nerve cells or between nerve cells and muscles relies on small electrical impulses. A cup of romaine lettuce juice contains 618 milligrams of potassium, or 13 percent of the recommended daily intake set by the Institute of Medicine.