Potassium works to balance out the sodium in your diet. An adequate potassium intake can lower systolic pressure ~4.4 mm Hg and diastolic pressure ~2.5 mm Hg.
Good potassium sources:
Cantaloupe, bananas, dates, nuts, oranges, and green leafy vegetables
Maintaining an adequate intake of potassium is especially important if you are taking diuretics. Some diuretics increase potassium loss via the kidneys.