January 5, 1996
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Potassium tablets may greatly reduce high blood pressure and its consequences in African-Americans who do not eat enough fresh fruit and vegetables and other potassium-rich foods, a Johns Hopkins study concludes.
"Potassium supplements produced a striking reduction in blood pressure," says Frederick Brancati, M.D., the study's lead author and an assistant professor of internal medicine. "The magnitude of the average reduction is all the more impressive given the participants' relatively low blood pressure before the study."
Supplements of potassium, a mineral that helps regulate heart rhythm and other functions, or even eating potassium-rich foods may be a safe, cheap and effective way to fight high blood pressure's complications, such as stroke and heart failure, which affect African Americans at an unusually high rate, says Brancati.
The study, published in the Jan. 8 issue of Archives of Internal Medicine, included 87 African American adults without high blood pressure. They were restricted to a low-potassium diet and given either potassium tablets or a placebo for 21 days. Blood pressure measurements were taken before and during the study. Urine tests were taken to monitor how much potassium the participants were taking.
The results showed that the potassium-tablet group had an average decrease in systolic blood pressure of 6.9 mm Hg and an average decrease in diastolic blood pressure of 2.5 mm Hg. The blood pressure lowering effects increased over the 21 days of the study, according to the results. The participants' average blood pressure before the study was 125/78 mm Hg. Systolic pressure is the blood pressure measured when the heart beats, while diastolic pressure measures blood pressure between successive heart beats. The findings were not influenced by age, gender, body weight and alcohol use.
Further research is needed to determine if potassium's blood-pressure lowering effect in healthy African Americans is long term, whether it can be achieved with smaller supplements or by eating potassium-rich foods without supplements, and whether it can benefit other ethnic groups and those with high blood pressure, says Brancati.
Although scientists have investigated a possible link between potassium and blood pressure since 1921, this is believed to be the first randomized, double-blind, placebo-controlled study to demonstrate the blood-pressure lowering effects of potassium supplements in healthy African Americans adults who have a diet low in potassium, the Hopkins scientists say.
A low-potassium diet is common among African Americans, according to epidemiologic studies. Foods rich in potassium include lean meat, whole grains, beans and fresh produce. It is unclear why potassium supplements cause a greater decline in blood pressure in African Americans than whites, but African Americans may benefit either because they are inherently sensitive to potassium or because they generally eat low-potassium foods, the scientists say.
Other authors of the study were Lawrence Appel, M.D., Alexander Seidler, Ph.D., and Paul Whelton, M.D. The study was supported by the American Heart Association, the National Institutes of Health and the National Kidney Foundation.