The quality of evidence is downgraded by inconsistency (variability in results).
A Cochrane review 1[Abstract] included 6 studies with a total of 483 subjects. Meta-analysis of 5 studies (n=425) indicated that potassium supplementation compared to control resulted in a large but statistically non-significant reductions in systolic blood pressure (MD -11.2 mmHg, 95% CI -25.2 to 2.7) and diastolic blood pressure (MD -5.0 mmHg, 95% CI -12.5 to 2.4).
A systematic review 2 included 33 RCTs with a total of 2 565 subjects (1 560 hypertensive, 1 005 normotensive). There were 3 crossover studies with open design, 2 crossove studies with blinded design, 16 crossover studies with double blind design, 4 parallel open, 1 parallel single, and 7 parallel double blind studies. The net changes from pre-treatment to end of follow-up urinary excretion of sodium and potassium, body weight, and blood pressure were assessed. Overall pooled estimate of effect of potassium supplementation on systolic and diastolic blood pressure (BP) were -4.44 mmHg (95% CI -2.53 to - 6.36, p<0.001) and -2.45 mmHg (95% CI -0.74 to -4.16, p<0.01). Exclusion of an outlier reduced overall pooled effect size estimates to -3.11 (-1.91 to -4.31) and -1.97 (-0.52 to -3.42). Effects of treatment appeared to be enchanced in studies in which participants were concurrently exposed to a high intake of sodium.
A systematic review and meta-analyses 3 included 22 RCTs with a total of 1 606 subjects and 11 cohort studies with a total of 127 038 subjects. Increased potassium intake reduced systolic BP by 3.49 mmHg (95% CI 1.82 to 5.15) and diastolic BP by 1.96 mmHg (95% CI 0.86 to 3.06) in adults. Reduction of BP was seen in people with hypertension but not in those without hypertension. Systolic blood pressure was reduced by 7.16 mmHg (1.91 to 12.41) when the higher potassium intake was 90-120 mmol/day, without any dose response. Increased potassium intake had no significant adverse effect on renal function, blood lipids, or catecholamine concentrations. Higher potassium intake reduced the risk of stroke (RR 0.76, 0.66 to 0.89). Associations between potassium intake and incident cardiovascular disease or coronary heart disease were not statistically significant.
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