|ORAL POTASSIUM LOWERS BLOOD PRESSURE
Even small amount of potassium may delay onset of high blood pressure
July 2, 1997
CHICAGO-Oral intake of potassium can significantly reduce blood pressure, according to an article in this week's issue of The Journal of the American Medical Association (JAMA).
Paul K. Whelton, M.D., M.Sc., formerly with The Johns Hopkins University School of Hygiene and Public Health and School of Medicine, Baltimore, Md., and colleagues analyzed a wide body of research on oral potassium intake and its effect on blood pressure. Their intent was seek resolution to the question of whether potassium is effective in controlling high blood pressure and the degree to which it might be effective.
The authors write: "It has been suggested that potassium supplementation results in reduction of systolic and diastolic blood pressure, yet the role of potassium supplementation in treating and preventing high blood pressure remains controversial. In part, this may be because some large and rigorously designed trials in hypertensive and non-hypertensive subjects are among those yielding the least impressive results."
When the researchers combined the results of 33 randomized controlled trials with 2,609 participants in which potassium supplementation was the only difference between the intervention and control conditions, they found potassium was effective in lowering blood pressure.
The analysis found a significant reduction in mean systolic (the first number of the blood pressure reading) and diastolic (the second number) blood pressure. Potassium intake resulted in a mean drop of 3.11 millimeters of mercury (mm Hg) for the systolic reading and 1.97 mm Hg for the diastolic reading. The potassium appeared to be particularly effective in studies in which participants were concurrently exposed to a high intake of sodium.
The authors conclude that even a small amount of potassium intake may play an important role in forestalling the onset of high blood pressure and that increased potassium intake should be considered as a recommendation for the prevention and treatment of high blood pressure, especially in those who are unable to reduce their sodium intake.
The authors write: "Oral potassium supplementation appeared to be well tolerated in all studies included in our meta-analysis, although only two reports provided specific accounting of type and frequency of treatment related adverse effects. Adverse effects in these two trials were fairly inconsequential and primarily consisted of abdominal pain, belching and flatulence (although only one individual stopped taking potassium because of gastrointestinal tract symptoms)." Adverse effects reported in another study included stomach pains, bright-red blood in stools, nausea or vomiting, and diarrhea.
They add: "Although most of the clinical trial experience to date emanates from studies in which potassium was administered in pill form as a chloride salt, there is little reason to suspect a different outcome after dietary supplementation and/or administration of other potassium salts provided potassium itself is sufficiently increased."
Information cited in the article shows that in 1928, a clinical trial of potassium supplementation in hypertension was reported. Since then, almost 60 reports of the blood pressure-lowering effects of potassium in humans have been published, about half randomized controlled trials, and most too small for definitive results. The researchers say pooling of results allows more precise estimates of intervention effect and exploration of the basis for outcome heterogeneity.
The technical details of the JAMA article follow and are taken from the official abstract.
Effects of Oral Potassium on Blood Pressure: Meta-analysis of Randomized Controlled Clinical Trials [JAMA. 1997;277:1624-1632]
Paul K. Whelton, MD, MSc; Jiang He, MD, PhD; Jeffrey A. Cutler, MD, MPH; Frederick L. Brancati, MD, MHS; Lawrence J. Appel, MD, MPH; Dean Follmann, PhD; Michael J. Klag, MD, MPH
The objective of the study was to assess the effects of supplementation with oral potassium on blood pressure in humans. This was accomplished by performing a Meta-analysis of randomized controlled trials described in English-language articles published before July 1995. Thirty-three randomized controlled trials (2609 participants) in which potassium supplementation was the only difference between the intervention and control conditions were selected.
Using a random-effects model, findings from individual trials were pooled, after results for each trial were weighted by the inverse of its variance. An extreme effect of potassium in lowering blood pressure was noted in 1 trial. After exclusion of this trial, potassium supplementation was associated with a significant reduction in mean (95% confidence interval) systolic and diastolic blood pressure of -3.11 mm Hg (-1.91 to -4.31 mm Hg) and -1.97 mm Hg (-0.52 to -3.42 mm Hg), respectively. Effects of treatment appeared to be enhanced in studies in which participants were concurrently exposed to a high intake of sodium.
The scientists concluded, "our results support the premise that low potassium intake may play an important role in the genesis of high blood pressure. Increased potassium intake should be considered as a recommendation for prevention and treatment of hypertension, especially in those who are unable to reduce their intake of sodium."