It is known that potassium levels and blood pressure are inversely related. Whelton and colleagues conducted a meta-analysis to determine the effects of supplementation with oral potassium on blood pressure.

Studies were included in the analysis if they were based on human experimentation, had randomly assigned study participants to groups, had a control group that was not substantively different from the treatment group and reported mean changes in blood pressure. In the 33 trials analyzed, the median length of treatment was five weeks. The median amount of daily potassium supplementation was 75 mmol. Pretreatment blood pressures averaged 147/95 mm Hg.

The groups treated with potassium had an average change in systolic blood pressure from a decrease of 41.0 to an increase of 2.8 mm Hg and changes in diastolic blood pressure from a decrease of 17.0 to an increase of 4.8 mm Hg. In one third of the trials, the change in blood pressure was statistically significant. There were no significant adverse effects. The size of the effect of potassium on blood pressure was small (a decrease of 3.1 mm Hg for systolic blood pressure and a decrease of 1.97 mm Hg for diastolic blood pressure).

The authors conclude that this and previous studies support the idea that potassium supplementation has a role in the treatment of hypertension. However, further studies are clearly needed.