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Banana's Appeal Ripens for Blood Pressure

New research shows potassium-rich foods may lower your risk of stroke

MONDAY, July 23, 2001 (HealthDayNews) -- While you're munching on that apple a day to keep to the doctor away, think about wolfing down a banana as well: High-potassium foods, like bananas, may lower your risk of stroke.

Researchers from Tulane University found that folks with a low dietary intake of potassium are up to 28 percent more likely to have a stroke than those who include potassium-rich fruits and vegetables in their daily diet.

"Our study examined the association between potassium in the diet and subsequent risk of stroke…and those who had the lowest [potassium] intake were shown to be at increased risk, while those who consumed more did not have this same elevated risk," says Lydia Bazzano, the lead study author and an epidemiologist at Tulane University School of Public Health and Tropical Medicine.

According to the study, low intake was defined as less than 1,500 mg of potassium daily. The recommended daily intake is about 2,300 mg, and the average American eats around 2,500 mg every day. A banana, one of the highest sources, has about 400 mg of potassium, as does a glass of orange juice, a cup of cantaloupe or a baked potato.

Although no one is sure exactly how potassium protects against stroke, many believe a link to blood pressure is key. Indeed, studies show that potassium can relax blood vessels, which cuts the risk of high blood pressure, and it also helps remove sodium from the blood, according to stroke expert Dr. Mitchell Elkind.

"People who are taking in more potassium are getting rid of more sodium, which in turn is lowering their blood pressure. And it is probably the lowered blood pressure that in the end is reducing the risk of stroke," says Elkind, a neurologist at Columbia Presbyterian Medical Center.

What made this study particularly interesting, however, was that potassium appeared to also offer protective effects to those whose blood pressure was normal.

"The statistical methods we used [in analyzing study results] suggested an independent effect," says Bazzano.

Although Elkind believes potassium may have played a role, he doesn't believe it tells the whole story.

"It seems that the people in the study who ate more potassium also were more active; they had less hypertension, less diabetes, less of the other factors that increase the risk of stroke. So their higher intake of potassium could simply be a reflection of a healthier lifestyle overall that, in turn, may be the real underlying factor in the reduced risk of stroke," he says.

The observational study included 9,800 American men and women who were originally part of the National Health Examination Survey (NHANES I) Epidemiologic Follow-up Study. The study relied on a 24-hour dietary recall, in which participants were asked to remember both their total caloric intake and the foods they ate. Using medical records and death certificates, the researchers obtained information on both stroke and cardiovascular disease among the participants. The original NHANES I began in 1971, and various follow-ups are continuing.

Over the course of this 19-year follow-up, 927 of the participants had a stroke, while 1,847 developed some form of heart disease. When this data was compared to the dietary information provided during the study, the relationship between stroke and potassium was noted.

"Participants who consumed the least amount of potassium per day [less than 1,500 mg] were at increased risk of stroke, while those who consumed more than that level did not show an elevated risk," says Bazzano.

Perhaps not coincidentally, Bazzano adds, low potassium diets have been found most commonly in the south, particularly among African-Americans living in the south -- a group that has among the highest risk of stroke.

The Tulane study is in the July issue of the American Heart Association journal, Stroke.

Because the research focused solely on dietary intake of potassium, it couldn't tell anything about how protective potassium supplements were -- and doctors warn not to try supplements without medical supervision.

"Excess potassium is excreted in the urine if one has healthy kidneys, but even healthy kidneys can be overwhelmed. And potassium [in very high doses] can be toxic to the heart…so it is important to have supervision, if potassium is to be supplemented in pill form," cautions Bazzano.

Elkind concurs: "This study does provide some interesting information that may one day lead to use of potassium supplements. But from what we know now, it would be premature to tell people to use potassium supplements to prevent stroke -- I would not recommend it routinely."

What To Do

"At this point, what we would recommend people do is eat a diet rich in fruits and vegetables high in potassium, along with a low-fat, low-sodium diet," says Elkind, who believes these are the dietary factors that can decrease your risk of stroke.

Bazzano agrees: "While dietary change is a simple solution, it can be difficult to implement and stick to. But we believe that increasing foods high in potassium will be very effective in reducing the risk of stroke."

To find a listing of potassium content in foods, plus a list of the highest dietary sources, click here.

For a sample diet containing foods that studies have shown can reduce high blood pressure, click here.

SOURCES: Interviews with Lydia Bazzano, Ph.D., epidemiologist, Tulane University School of Public Health and Tropical Medicine, New Orleans, and lead study author; Mitchell Elkind, M.D., neurologist, Columbia Presbyterian Medical Center, and associate professor of neurology, Columbia University College of Physicians and Surgeons, New York City; July 2001 Stroke
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