Postmenopausal women who get more potassium in their diets are less likely to have a stroke or die than those who don't get as much, according to a new study. Potassium-rich diets have been linked to lower blood pressure before, but this is the first time potassium has been tied to stroke risk, said senior author Sylvia Wassertheil-Smoller of the Department of Epidemiology and Population Health at Albert Einstein College of Medicine in New York.
Her team analysed data from the Women's Health Initiative study on 90,137 postmenopausal women, ages 50 to 79. At one and three years after enrolment, the women filled out dietary questionnaires.
Overall, they stayed in the study for an average of 11 years. The researchers used the dietary questionnaires and potassium values for common foods to determine that the women consumed an average of 2,611 milligrams of potassium per day.
According to Food and Drug Administration labels, adolescents and adults should be consuming at least 4,700 mg of potassium daily. Bananas, avocados and other fruits and vegetables are good sources of potassium. A medium-sized banana has about 420 mg of potassium, while a cup of avocado has 708 mg.
The researchers then divided the women into four groups based on potassium consumption, from those who got less than 1,926 mg per day, the least potassium, to those who got more than 3,194 mg per day, the most.
Each year, out of every 1,000 women in the study, about three suffered a stroke and nearly 12 died of any cause. Women who ate the most potassium were 12 percent less likely to suffer a stroke and 10 percent less likely to die during the study period than those who ate the least, according to results in Stroke.
"Potassium is a vital component of cellular function," Wassertheil-Smoller said. "It affects endothelial cells which line blood vessels, so perhaps it may provide more blood flow to critical areas - that is one thought, but we don't really know."
The effect was strongest for women without high blood pressure, which was surprising, Wassertheil-Smoller told Reuters Health by email.
"This and previous observational studies cannot prove that it is potassium that lowers stroke risk," said Susanna C. Larsson of the Institute of Environmental Medicine at Karolinska Institutet in Stockholm, Sweden.
Larsson was not involved in the new research.
"It may be other nutrients or combinations of nutrients in potassium-rich foods that are protective," she told Reuters Health by email.