Effect of potassium supplementation on blood pressure in African Americans on a low-potassium diet: A randomized, double-blind, placebo-controlled trial

Objective: To determine the effect of potassium supplementation on blood pressure in African Americans consuming a low-potassium diet. Design: Randomized, double-blind, placebo-controlled 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 (all P>.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.