Epidemiologic surveys, experimental studies in animals, and clinical trials in young and middle-aged patients with
hypertension indicate that
dietary potassium lowers blood pressure. The mechanism of the
antihypertensive effect is not well defined. Variations in serum
potassium within the physiologic range may directly affect vascular smooth muscle tone.
Potassium may also influence the regulation of blood pressure through effects on
sodium handling,
aldosterone secretion, the renin/angiotensin system, renal
kallikrein,
eicosanoids, and
atrial natriuretic peptide. This study was undertaken to confirm the blood pressure-lowering effect of
potassium in older patients and to determine the mechanism of the
antihypertensive effect. Twenty-two patients greater than or equal to 60 yr of age were admitted to a Clinical Research Unit for 8 days after a 2-wk period free of
antihypertensive medication. Patients were placed on an isocaloric diet containing 200 mmol/day of Na+, 70 mmol/day of K+, and 500 mg/day of Ca2+ and were treated in a randomized, double-blinded manner with either
potassium chloride (120 mmol/day) or placebo. After 4 days, patients were crossed over to the alternate treatment. Systolic blood pressure decreased 8.6 mm Hg (95% confidence interval -14.6, -2.6), and diastolic blood pressure decreased 4.0 mm Hg (-6.9, -1.0) during
potassium chloride supplementation. There was no significant change in blood pressure during treatment with placebo. Serum K+ was 3.9 +/- 0.1 mmol/L after 3 days of placebo and 4.3 +/- 0.1 after 4 days of
potassium chloride (P less than 0.002). Urinary
sodium excretion averaged 192 +/- 11 mmol/day after placebo and 221 +/- 8 after
potassium treatment (P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)