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A Randomized, Double-blind, Placebo-Controlled Trial

Frederick L. Brancati, MD, MHS; Lawrence J. Appel, MD, MPH; Alexander J. Seidler, PhD; Paul K. Whelton, MD, MSc

Arch Intern Med. 1996;156(1):61-67.

Abstract
Objective
To determine the effect of potassium supplementation on blood pressure in African Americans consuming a low-potassium diet.

Design
Randomized, double-blind, placebocontrolled trial with two parallel arms.

Setting
Community-based research site.

Participants
Eighty-seven healthy African Americans aged 27 to 65 years with a systolic blood pressure between 100 and 159 mm Hg and a diastolic blood pressure between 70 and 94 mm Hg.

Intervention
During the 21-day intervention period, all participants were provided with a low-potassium diet (32 to 35 mmol/d). In addition to this diet, they were randomly assigned to receive either potassium supplements (80 mmol/d) or placebo.

Main Outcome Measure
Change in blood pressure in the potassium vs the placebo group, based on a total of nine blood pressure readings at three visits. Blood pressures were taken before and during the intervention by means of random-zero sphygmomanometry.

Results
At baseline, the placebo and potassium groups were similar for mean blood pressure (127/78 vs 125/77 mm Hg), 24-hour urinary potassium excretion (50 vs 44 mmol), and all other variables measured (allP>.05). During the intervention, the net difference in 24-hour urinary potassium excretion between groups was 70 mmol. Compared with the placebo group, the potassium supplementation group experienced a net decline in systolic blood pressure of 6.9 mm Hg (95% confidence interval, —9.3 to —4.4 mm Hg; P<.001) and a decline in diastolic blood pressure of 2.5 mm Hg (95% confidence interval, —4.3 to —0.8 mm Hg; P=.004). Simultaneous adjustment for differences in baseline characteristics only strengthened these estimates.

Conclusions
Potassium supplementation reduces blood pressure substantially in African Americans consuming a diet low in potassium. Increased potassium intake may play an important role in reducing blood pressure in this population at high risk for hypertension.

(Arch Intern Med. 1996;156:61-67)

Author Affiliations
From the Welch Center for Prevention, Epidemiology, & Clinical Research, The Johns Hopkins Medical Institutions, Baltimore, Md.

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