2 Bananas a Day May Keep Stroke Away, Study Says

An extra banana or helping of fresh broccoli a day could provide important protection against death from stroke, a new study by the UC San Diego School of Medicine indicates.

The findings show that a diet high in potassium--commonly found in fresh fruits and vegetables--can lower the risk of stroke as much as 40%, regardless of other risk factors, Dr. Elizabeth Barrett-Connor, the study’s co-author, said here Wednesday.

Barrett-Connor and co-author Kay-Tee Khaw, an epidemiologist at both UCSD and Cambridge University School of Medicine in England, published their results in today’s New England Journal of Medicine.

While Barrett-Connor called the results important, she cautioned Wednesday that the conclusions do not justify individuals taking potassium supplements in a pill, or non-food, form.

A high-potassium diet per se cannot categorically be recommended as an effective way to prevent stroke based on the single study, Barrett-Connor said.

“But in the context of fresh fruits and vegetables being helpful in possibly preventing cardiovascular disease and some forms of cancer as well, an extra helping (of potassium-rich foods) is in no way harmful to the general public and could be quite beneficial,” she said.

“A supplement could possibly interfere with something else (biochemically in the body) and I don’t think people should be fooling around with potassium that way.” She added that people with kidney or hypertension problems should talk first with their doctors before changing their diets.

Barrett-Connor and Khaw based their findings on data provided from an ongoing UCSD population study of heart and chronic disease, and the associated risk factors, of more than 5,000 residents living in the San Diego community of Rancho Bernardo. The study began in 1972.

The potassium data came from 859 white men and women between the ages 50 and 79.

In 1975, the participants were asked detailed questions by dietitians about what they had eaten during the previous 24 hours, the size of portions, and whether or not the diet was representative of their daily intake. The information was then coded for trace minerals, vitamins and other nutrients using a computer program from the Nutrition Coordinating Center at the University of Minnesota. Since then, on a yearly basis, the participants have been followed to correlate the nutrition information with any diseases that have subsequently developed.

After 12 years, the 24 individuals who died of stroke had had significantly lower dietary potassium intake than those still living or those who died from causes other than stroke, Barrett-Connor said.

The results, she said, are striking because the researchers came up with strong correlations despite working with a relatively small sample group.

In an epidemiological study, limitations due to small numbers usually result in correlations being made weaker, not stronger, she said. She said the reason “I feel so strong about our results is that we found such a powerful association despite the small numbers.”

The reason for potassium having an apparent effect in preventing stroke is not clear from the study. Clinical work previously published by Khaw indicates that potassium lowers blood pressure. But Barrett-Connor said that any stroke-prevention action by potassium works independently of the effect that potassium has on lowering blood pressure. She said individuals with a high dietary potassium level had a lower risk of stroke--independent of their blood pressure.

She said that relationship held true even for people who smoked, who were older, who had higher blood-cholesterol levels and other factors generally associated with higher risk of stroke.

Barrett-Connor said the stroke death rate in the United States--the country’s third-leading cause of death behind heart attacks and cancer--has been on the decline since the late 1940s, when consumption of fresh fruits and vegetables began to increase among the population as a whole. She said today’s results may help explain the phenomenon.

Because a clinical study relating potassium intake to stroke prevention is not feasible, Barrett-Connor hopes that directors of large population-based studies will examine their dietary data for associations between potassium intake and stroke prevention. Among those studies is one of 2,000 Western Electric workers in Chicago who have been followed medically since the late 1950s.