The effect of potassium supplementation in persons with a high-normal blood pressure: Results from phase I of the Trials of Hypertension Prevention (TOHP)

We conducted a randomized, double-blind, placebo-controlled trial oral potassium chloride supple mentation (60 mmol/d) in 353 men and women with an initial average diastolic blood pressure between 80 and 89 mm Hg. In the active (n = 178) campared to the placebo (n = 175) treatment group, the urinary potassium level was significandy (p < 0.001) increased by an average of 44.0 and 42.3 mmol/24 h following 3 and 6 months of therapy, respectively. Compared to placebo, active treatment was associated with a small (mean = 1.8 mm Hg) but significant (p = 0.04) reduction in diastolic blood pressure following 3 months of therapy. Following 6 months, however, this apparent treatment effect had virtually disappeared (mean reduction in diastolic blood pressure = 0.3 mm Hg). There was no significant effect of potassium supplementation on systolic blood pressure at either follow-up visit. There was a significant, independant, dose-response relationship between change in both 24-hour urinary potassium excretion and urinary sodium-potassium ratio and the corresponding change in diastolic blood pressure (−1.49 mm Hg for the highest versus the lowest quartile of change in urinary potassium excretion).