Foods high in potassium help lower blood pressure, and more important, stabilize it. If you're on a diuretic such as hydrocholorothiazide (HCTZ) to reduce your bp, it becomes even more important to keep your potassium intake up, as HCTZ flushes out potassium along with the sodium that you want it to. In fact if you lose too much potassium, your bp will go up and/or become unstable.