Potassium in untreated hypertension: clinic readings moved more

Researchers at Universidad Peruana Cayetano Heredia in Lima systematically reviewed randomised parallel and crossover trials in adults with untreated primary hypertension, that is, high blood pressure not yet treated with medicine. The trials compared oral potassium supplements with placebo, sodium chloride or no treatment. The review, published online in the Journal of the American Heart Association on 30 October 2026, was registered in advance (PROSPERO CRD42024621287) and covered searches up to 1 October 2025. It found 19 trials with 803 participants in total; 14 were crossover trials, a design in which the same participants receive both options in turn, and the median treatment lasted four weeks.

The clinic reading moved more than the 24-hour one

Measured in the clinic, potassium lowered systolic pressure by 5.3 mm Hg (95% CI 4.4 to 6.3) and diastolic pressure by 4.5 mm Hg (95% CI 3.9 to 5.1) compared with the control conditions. With 24-hour ambulatory monitoring, where a cuff takes readings through the day and night, the differences were smaller: 2.8 mm Hg systolic (95% CI 1.3 to 4.3) and 3.2 mm Hg diastolic (95% CI 2.2 to 4.2). The authors call the clinic effect modest and note that the ambulatory evidence came from fewer data.

The direction matches an earlier review. In The BMJ in 2013, a meta-analysis of 22 randomised trials with 1,606 participants found that higher potassium intake lowered systolic pressure by 3.49 mm Hg and diastolic by 1.96 mm Hg in adults, an effect seen in people with hypertension but not in those without it.

Side effects were four times as common

Adverse events were reported in 12.8% of people on potassium against 3.2% on the comparison, although few participants stopped because of them. The abstract does not list what those events were, and the authors describe the safety data as limited. Heterogeneity between trials was substantial.

The 2013 review drew its own boundary on who the finding applies to: the authors wrote that more potassium was potentially beneficial for most people "without impaired renal handling of potassium". The new review included only adults with untreated primary hypertension and did not evaluate potassium supplements alongside blood pressure medicines.

Pressure fell, but events were not measured

The abstract of the new review reports blood pressure readings, not strokes or heart attacks, and with a median treatment of four weeks it cannot show whether supplements change those long-term outcomes. Evidence on events comes from a different kind of potassium. In SSaSS, published in the New England Journal of Medicine in 2021, 600 villages in rural China were randomly assigned either to a salt substitute in which part of the sodium chloride was replaced with potassium chloride, or to regular salt. Among 20,995 people who had had a stroke or were 60 or older with high blood pressure, followed for an average of 4.74 years, the substitute group had fewer strokes (29.14 against 33.65 per 1,000 person-years; rate ratio 0.86, 95% CI 0.77 to 0.96) and fewer deaths (rate ratio 0.88, 95% CI 0.82 to 0.95). Serious adverse events attributed to clinical hyperkalaemia (high blood potassium) were not significantly more frequent (rate ratio 1.04, 95% CI 0.80 to 1.37). The trial was open-label, and it changed sodium and potassium at the same time, so it cannot say how much of the effect came from potassium.

So the new paper narrows rather than settles the question: in short trials, potassium supplements moved clinic blood pressure by a few millimetres in people who were not yet on treatment, and less so over 24 hours. The available abstract does not report who funded the review; SSaSS was funded by the National Health and Medical Research Council of Australia. These short trials do not establish who should take potassium supplements, and given the 2013 review's caveat about kidney function, that is worth discussing with your doctor.

This material is for information only and does not replace a consultation with a doctor.

Sources

• Ravichagua Ashiyama J, Medina FA, Loza C, Poterico J, Ramirez Sanchez S. Oral potassium supplementation lowers clinic blood pressure in untreated primary hypertension: systematic review and meta-analysis of randomized trials. J Am Heart Assoc. 2026. PMID 42960746 · DOI 10.1161/JAHA.125.048590

• Aburto NJ, Hanson S, Gutierrez H, Hooper L, Elliott P, Cappuccio FP. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013;346:f1378. PMID 23558164 · DOI 10.1136/bmj.f1378

• Neal B, Wu Y, Feng X, et al. Effect of salt substitution on cardiovascular events and death. N Engl J Med. 2021;385(12):1067-1077. PMID 34459569 · DOI 10.1056/NEJMoa2105675