Potassium and Blood Pressure: What the Trials Show

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Potassium is sold both as a blood-pressure supplement and as a reason to change the salt in the kitchen. Those are not the same intervention. A tablet, a salt substitute, and a potato can all contain potassium, and the trials below do not treat them as interchangeable.

How much potassium people actually get

The National Academies set the potassium adequate intake at 3,400 mg a day for men 19 and older and 2,600 mg a day for women 19 and older. The NIH Office of Dietary Supplements reports 2013–2014 survey averages from food of 3,016 mg a day for men 20 and older and 2,320 mg a day for women. Those averages are below the targets. They are not a count of how many people miss the target, and this page does not use a “fewer than 5 percent” figure.

What the blood pressure trials show

A WHO-commissioned review pooled 22 randomized trials (1,606 adults) and 11 cohort studies (127,038 adults). More potassium lowered systolic pressure by 3.49 mm Hg (95% CI 1.82 to 5.15) and diastolic pressure by 1.96 mm Hg (95% CI 0.86 to 3.06) in adults. The blood-pressure effect was seen in people with hypertension and not in people without it. When the higher intake was 90 to 120 mmol a day, systolic pressure fell by 7.16 mm Hg. The same review found no clear harm to kidney function, blood lipids, or catecholamines in adults, and a 24% lower stroke risk in the cohorts (risk ratio 0.76, 95% CI 0.66 to 0.89). It did not find a significant link with cardiovascular disease or coronary heart disease overall (Aburto 2013; PMID 23558164).

Salt substitutes and the DASH diet

The Salt Substitute and Stroke Study assigned 20,995 people in rural China, with a prior stroke or age 60-plus and high blood pressure, to a salt that was 75% sodium chloride and 25% potassium chloride, or to regular salt. Over a mean 4.74 years, the salt substitute lowered stroke (rate ratio 0.86, 95% CI 0.77 to 0.96), major cardiovascular events (0.87, 95% CI 0.80 to 0.94), and death (0.88, 95% CI 0.82 to 0.95). Serious events attributed to high potassium were not significantly higher (). That trial changed the salt in the food. It is not a reason to swallow potassium tablets.

A separate dose-response meta-analysis of 85 sodium-reduction trials found an approximately linear drop in blood pressure across the sodium intakes studied, with no flattening at the low end, and a steeper drop in people with hypertension (PMID 33586450). The original DASH trial, which kept sodium constant, lowered systolic pressure by 5.5 mm Hg and diastolic by 3.0 mm Hg versus a typical US control diet. In the 133 participants who already had hypertension, the drops were 11.4 and 5.5 mm Hg (PMID 9099655). DASH is a whole eating pattern, not a potassium pill.

Why a potassium pill is a weak fix

Most potassium-only supplements contain up to 99 mg. The NIH fact sheet says manufacturers often stop there because the FDA has warned about small-bowel injury from some potassium chloride drugs above 99 mg. The FDA has not set a supplement cap in that fact sheet, but 99 mg is about 2% of the daily value and does not close a gap of hundreds of milligrams. Prescription potassium is a different product and needs a blood test.

Who should not add potassium

NIH ODS says potassium-sparing diuretics can raise potassium, while some water pills waste it. ACE inhibitors and ARBs also hold potassium in. Adding a supplement, or a potassium salt substitute, on top of those drugs can be dangerous. People with advanced kidney disease are in the same group. This is not advice to stop a prescribed potassium pill.

Food amounts from the NIH table

The NIH food table lists about 610 mg in one medium baked potato, flesh only; about 607 mg in one cup of canned kidney beans; and about 422 mg in one medium banana. Those three foods move intake more than a 99 mg tablet. Spinach and avocado are often named too, but this page only quotes the amounts printed on that table.