Scientists tried to figure out how much of the blood pressure drop in a big study was due to eating less salt versus eating more potassium — and they found it’s hard to say exactly how much each one helped, because the numbers varied a lot depending on how they did the math.

When people used a special salt substitute with less sodium and more potassium, their blood pressure dropped more than scientists expected just from lowering salt — suggesting the extra potassium might be helping out in a way that’s more than just adding two effects together.

Cutting back on salt can lower blood pressure, but sometimes it doesn’t do much at all—why? It depends on the person, how you measure it, and how much potassium they eat.

When people ate more potassium, their blood pressure went down a little—but the amount it dropped varied a lot depending on which study you looked at, so we’re not sure exactly how much potassium helps lower blood pressure.

Different studies say reducing salt lowers blood pressure by wildly different amounts—some say almost nothing, others say a bit more—so we’re really not sure how much of an effect salt really has.

Cutting down on salt lowers blood pressure more for people who already have high blood pressure than for those with normal blood pressure—about 2.5 times more.