Peeling Away Stroke Risk
Bananas can help fill potassium quota, study finds
MONDAY, Aug. 12, 2002 (HealthDayNews) -- If an apple a day keeps the doctor away, what will a banana a day keep away?
A stroke, possibly. Bananas are a rich source of potassium, and a new study adds to the evidence linking low blood potassium levels to an increased risk of stroke.
A high level of potassium intake seems especially important for people who are taking diuretics, the "water pills" given for high blood pressure, says Dr. Steven R. Levine, a stroke expert at Mount Sinai School of Medicine and co-author of an editorial accompanying the report in tomorrow's issue of Neurology. Most diuretics wash a lot of potassium out of the body, he explains.
"In this study, the risk of stroke was increased only for people with low blood potassium levels who were taking diuretics," Levine says. "It is very important for people who are on diuretics to make sure they take in more potassium."
Levine suggests what he calls a "potassium cocktail," consisting of a banana, two tomatoes and a glass of orange juice.
One reason for the study, says a statement by study author Dr. Deborah M. Green, a neurologist at the Queen's Medical Center Neurosciences Institute in Honolulu, was to test the interplay of diuretics and dietary potassium.
"Diuretics clearly help prevent stroke by controlling high blood pressure, but we wanted to see whether their effect on potassium levels would affect the risk of stroke," she explains.
Green and her colleagues looked at data from the Cardiovascular Health Study, which includes nearly 6,000 residents of four states -- North Carolina, California, Maryland and Pennsylvania. They were followed for up to eight years, and the incidence of strokes was measured against their reports of dietary intake of potassium.
People with the lowest intake of potassium were 50 percent more likely to have a stroke than those with the highest dietary intake, the researchers report, with the risk concentrated among diuretic takers with low blood levels of potassium. Their stroke risk was 2.5 times greater than for diuretic takers with the highest blood levels of potassium.
Green stresses the results don't imply that diuretics create an excessive risk of stroke. "The question is whether diuretics would be even more effective with adequate potassium intake," she says.
This is not the first report linking low potassium with stroke, Levine notes. Just last year, analysis of data from the National Health Examination Survey Epidemiological Follow-Up Study of 9,800 people found those with a dietary intake of less than 1,500 milligrams a day (a banana has about 400 milligrams, as does a glass of orange juice and a cup of cantaloupe) were 28 percent more likely to have a stroke than those getting the recommended daily intake of 2,300 milligrams.
Levine isn't recommending potassium supplements rather than potassium-rich foods, because all the data about stroke risk comes from observational studies, which lack the scientific rigor needed to prove a case conclusively.
"Unless someone undertakes a clinical trial to give a high potassium diet or supplement and tease out the potentially confounding factors, it is difficult to make terribly strong recommendations," he says. "Potassium is so readily available in foods that we are highly unlikely to see a clinical trial done."
What can be said is that a daily banana, or glass of orange juice or slice of cantaloupe or a baked potato -- another good potassium source -- does no harm and might very well do good, Levine says.
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