For a few days, extra potassium lowers mice's blood pressure, but after three weeks, it starts to raise it again.

When mice eat a lot of potassium for three weeks, their blood pressure goes up mostly at night, no matter how much salt they eat or what form of potassium they consume.

Even though high potassium lowers a kidney transporter in mice, this doesn't explain the blood pressure changes, suggesting other mechanisms are at play.

Long-term high potassium makes a kidney channel more active, and blocking that channel with a drug lowers blood pressure in mice.

If people eat less salt and more potassium-rich salt, the extra potassium might lower their blood pressure more than cutting back on salt alone — and most of that drop seems to come from the potassium.

If you eat more potassium every day—like from bananas or potatoes—your blood pressure might drop just a tiny bit, but not enough to matter for your health if you don’t already have high blood pressure.