Potassium and Blood Pressure: What the Trials Found, and the Doses They Used

What the pooled trials found

A 2015 meta-analysis pooled 15 randomized trials in 917 people who were not taking blood-pressure medicines ^[2]. Potassium supplements lowered systolic pressure by 4.7 mmHg and diastolic by 3.5 mmHg; in people with high blood pressure the drops were 6.8 and 4.6 mmHg ^[2]. The effect tracked how much urinary potassium rose and how far the sodium-to-potassium ratio fell ^[2].

A 2017 meta-analysis limited to people with high blood pressure found reductions of 4.48 mmHg systolic and 2.96 mmHg diastolic ^[3]. The effect was larger in people with low potassium intake at baseline (under 90 mmol/day), higher sodium intake and no blood-pressure drug treatment ^[3].

Why one review disagreed

The 2006 Cochrane review included 6 small randomized trials (n=483) with 8 to 16 weeks of follow-up ^[4]. Pooling 5 of them, it found large reductions (11.2 mmHg systolic, 5.0 mmHg diastolic) that were not statistically significant, with big unexplained differences between trials ^[4].

Excluding one trial in an African population with very high baseline blood pressure shrank the reductions to 3.9/1.5 mmHg, and the 2 high-quality trials (n=138) alone were also non-significant ^[4]. The trials were few, short and inconsistent, which is why we grade this review C.

The doses behind those numbers

The trials gave prescribed amounts. The 2015 meta-analysis mostly used potassium chloride at 60 to 65 mEq/day, which ODS converts to 2,346 to 2,541 mg, for 4 to 24 weeks ^[1]. The 2017 analysis covered 1,173 to 4,692 mg/day for 4 to 15 weeks ^[1].

Over-the-counter supplements are a different product. Most potassium-only supplements contain 99 mg or less, about 2% of the Daily Value; we explain why in why potassium supplements stop at 99 mg ^[1].

Food is the realistic route for most people. The DASH eating pattern, which stresses fruits, vegetables and low-fat dairy, lowers blood pressure by an average of 5.5/3.0 mmHg and provides three times more potassium than the average American diet, though it also adds magnesium and calcium, so potassium's own share cannot be pinned down ^[1].

Salt substitutes: the biggest trial so far

The SSaSS trial randomized 600 villages in rural China; its 20,995 participants had a history of stroke or were 60 or older with high blood pressure ^[5]. Villages switched to a salt of 75% sodium chloride and 25% potassium chloride, or kept regular salt ^[5].

Over a mean of 4.74 years, stroke was lower with the substitute (rate ratio 0.86), as were major cardiovascular events (0.87) and death (0.88) ^[5]. Serious events from high blood potassium were not significantly more common ^[5]. The substitute both cuts sodium and adds potassium, so the trial cannot say how much each did.

Who should check first

Potassium can build up when the kidneys cannot clear it. ODS flags these groups and medicines:

• Impaired kidney function: very high potassium intakes can exceed the kidneys' capacity to excrete it ^[1].
• ACE inhibitors and ARBs (such as benazepril and losartan) reduce potassium excretion and can lead to high blood potassium ^[1].
• Potassium-sparing diuretics (such as amiloride and spironolactone) can cause high blood potassium ^[1].
• Loop and thiazide diuretics work the other way, raising potassium loss in urine ^[1].
• Salt substitutes hold about 440 mg to 2,800 mg of potassium per teaspoon, so they count too ^[1].