Controlled trial of long term oral potassium supplements in patients with mild hypertension. Placebo-controlled trial of potassium supplements in black patients with mild essential hypertension. Blood-pressure response to moderate sodium restriction and to potassium supplementation in mild essential hypertension. The influence of oral potassium citrate/bicarbonate on blood pressure in essential hypertension during unrestricted salt intake. Sodium restriction and potassium supplementation in young people with mildly elevated blood pressure.
A 15 week randomised double blind placebo controlled trial of oral potassium supplements (48 mmol daily) was conducted in 37 patients who had mildly increased blood pressure and a normal dietary intake of sodium. After a two month run in and a one week baseline period the patients were randomly assigned to receive either potassium supplements (n = 18) or placebo (n = 19). By the third week of treatment blood pressure in the actively treated group had decreased significantly compared with that in the placebo group, though the decrease reached its maximum after 15 weeks. Urinary potassium excretion increased significantly in the group who received potassium supplements, but no significant changes were found in plasma sodium and potassium concentrations or in urinary sodium excretion. In a subgroup of 13 patients who underwent a further nine weeks of treatment with oral potassium supplements at half of the previous dose (24 mmol daily) their blood pressure, at the end of this second study period, was still significantly lower compared with their baseline value but not with that of the placebo group. These results show that moderate oral potassium supplements are associated with a long term reduction in blood pressure in patients who have mild hypertension. Forty-eight black patients with mildly increased blood pressure (BP) that had not yet been subjected to treatment took part in a double-blind clinical trial of the efficacy and tolerability of oral potassium supplements (64 mmol daily) versus a matching placebo (made of starch with coating) in a 16-week study. Potassium supplements produced a significant decrease in mean supine and standing BP within 4 weeks after treatment inception. Urinary potassium excretion increased significantly in the 24 patients who received potassium supplements (p less than 0.001). No significant changes occurred in plasma sodium and potassium concentrations or in urinary excretion of sodium during the study. All patients completed the trial without experiencing any notable untoward effects. These results are consistent with the premise that oral potassium supplements may exert hypotensive effects of clinically significant degree in patients with mild hypertension. To determine whether moderate restriction of dietary sodium content or supplementation of potassium intake reduces blood-pressure in patients with mild essential hypertension, twelve patients were put on three different diets--a control diet (180 mmol sodium/day), a sodium restricted diet (80 mmol/day). Each diet was taken for at least 4 weeks and the sequence of the regimens was randomised. At the completion of each regimen intra-arterial pressure was recorded continuously, and vasoactive hormones were measured hourly, for 24 h, under standardised conditions, in hospital. Compared with the control diet, sodium restriction was associated with lower blood-pressure readings in seven patients, higher levels in five, and an overall reduction in mean pressures of only 4.0/3.0 mm Hg (not significant). Individual differences in blood-pressure between these two diets correlated closely with concomitant differences in plasma renin activity (r = 0.75). Potassium supplementation also resulted in variable changes in arterial pressure, and the mean difference in pressure recordings (0.1/0.8 mm Hg) was insignificant. The results show that moderate restriction of sodium intake or supplementation of dietary potassium has variable effects on arterial pressure in individuals with mild essential hypertension, and that overall the blood-pressure changes induced are very small. Responsiveness of the renin-angiotensin system may limit the fall in blood-pressure induced by sodium restriction. In several trials, a blood pressure lowering effect of potassium chloride could be demonstrated. However, it is not known if other potassium salts are also effective. In a randomized cross-over trial, 12 patients with essential hypertension were treated for 8 weeks with placebo and 120 mmol potassium per day. Potassium was given together with 50% citrate and 50% bicarbonate as anions. Urinary potassium excretion rose from 61.8 +/- 8.1 to 166.7 +/- 21.2 mmol/24 hours during potassium supplementation. However, blood pressure and heart rate remained unchanged when compared to placebo. Non-chloride potassium salts may not be effective in lowering blood pressure in essential hypertension. Since potassium rich foods like fruits and vegetables contain potassium mostly as non-chloride salts, it appears to be premature to recommend a high dietary potassium intake as a mean to treat elevated blood pressure. Forty young subjects, aged 18 to 28 years, with mildly elevated blood pressure participated in a double-blind randomized three-period crossover study of the effect of sodium restriction with and without potassium supplementation on blood pressure. Dietary sodium intake was restricted for 18 weeks in which the patients received in random sequence 'slow-sodium' (90 mmol/day), 'slow-potassium' (72 mmol/day), and placebo tablets, each for 6 weeks. Mean urinary sodium excretion was 129 mmol/24 h in the slow-sodium period, 57 mmol/24 h during placebo, and 69 mmol/24 h during slow-potassium. Mean supine systolic blood pressure in the sixth week of the slow-potassium period was 3.3 mmHg lower than that at the end of the slow-sodium period (P less than 0.05). There was no significant difference in systolic or diastolic blood pressure between the placebo and the slow-sodium periods. The fall in systolic blood pressure in the low sodium/high potassium period was accompanied by a fall in cardiac index of 0.4 l/min per m2 body surface area (BSA) (P = 0.03). Our observations suggest a small hypotensive effect of moderate sodium restriction combined with high potassium intake in young hypertensive subjects. Sodium restriction alone has little effect on blood pressure in this group. The combination of a low sodium/high potassium diet may lower blood pressure by affecting cardiac output. Reducing the dietary sodium:potassium ratio may therefore be useful in the management of early primary hypertension.
Potassium supplementation has no statistically significant effect on blood pressure. Due to small number of participants in the two high quality trials, the short duration of follow-up, and the unexplained heterogeneity between trials, the evidence about the effect of potassium supplementation on blood pressure is not conclusive. Further high quality RCTs of longer duration are required to clarify whether potassium supplementation can reduce blood pressure and improve health outcomes.