Older women can reduce their risk of stroke by ensuring their diet is rich in potassium, long known to lower blood pressure and now seen as a stroke risk reducing factor, a study suggests.

Aging women consuming a potassium-rich diet are less prone to having strokes than women whose diet contains less of the mineral, researchers at the Albert Einstein College of Medicine in New York City found.

Women consuming the most potassium showed a 12 percent reduction of their stroke risk, the researchers report in the American Heart Association's journal Stroke.

In the study, 90,137 women aged 50 to 79 were tracked for more than 11 years while their consumption of potassium was monitored.

During the period, the numbers who suffered strokes or who died was recorded.

On average, the women in the study consumed around 2,600 milligrams of potassium daily, well below federal health guidelines, the researchers found. However, those who consumed the most had the lowest incidence of stroke.

The results of the study were suggestive enough for the researchers to make a recommendation about diets for older women.

"Postmenopausal women should eat more potassium-rich foods, such as fruits, vegetables, beans, milk and unprocessed meats in order to lower their risk of stroke and death," said researcher Sylvia Wassertheil-Smoller of the college's department of population health and epidemiology.

Less than 2 percent of American adults consume the minimum recommended amount of potassium daily, a study headed by the U.S. Centers for Disease Control and Prevention found in 2012.

The mechanism involved in potassium's ability to decrease stroke risk isn't clear, the researchers said, although they have some theories.

"Potassium may play a role in improving blood vessel function in our brains," study lead author Arjun Seth says. "This could allow better oxygenation of our brain tissue, and prevent tissue death that occurs from lack of oxygen to the brain."

"The effect of potassium consumption on reduced stroke risk could also be due to a better diet overall, though we did not investigate this in our study."

Potassium is present in all the food groups, most especially fruits, but also in milk and milk products, and vegetables.

A banana of average size, for example, can provide around 430 milligrams of potassium.

"Our findings suggest that women need to eat more potassium-rich foods," says Wassertheil-Smoller. "You won't find high potassium in junk food."

However, she cautioned that excessive consumption of potassium can lead to heart problems, suggesting women monitor how much of the mineral they consume.