Potassium, an essential nutrient found in bananas, helps keep arteries healthy, say researchers from the University of Alabama at Birmingham.

In a mice study, researchers showed that mice fed reduced levels of dietary potassium had stiffer arteries and more vascular calcification than mice fed normal levels. In humans, arterial stiffness is a risk factor for heart disease and death from heart disease.

The UAB researchers also found that increased dietary potassium levels lessened vascular calcification and aortic stiffness.

The study was conducted using mice prone to atherosclerosis. These were apoliprotein E-deficient mice, and they are prone to cardiovascular disease when fed a high-fat diet.

The researchers found that mice fed a low-potassium diet had a significant increase in vascular calcification. In contrast, the mice fed a high-potassium diet had markedly less vascular calcification.

Also, the low-potassium mice had increased stiffness of their aortas, and high-potassium mice had decreased stiffness, which was measured by echocardiography in live animals.

"The findings demonstrate the benefit of adequate potassium supplementation on prevention of vascular calcification in atherosclerosis-prone mice, and the adverse effect of low potassium intake," said co-author Paul Sanders, M.D.

A recent study from the Keck School of Medicine of the University of Southern California found that higher potassium levels were associated with lower blood pressure. Although health experts urge patients with hypertension to lower their salt intake, the study found that potassium levels were associated with lower blood pressure regardless of salt intake.

"When dietary potassium is high, kidneys excrete more salt and water, which increases potassium excretion," said researcher Alicia McDonough. "Eating a high potassium diet is like taking a diuretic."

An earlier 10-year study at Boston University of the dietary habits of 2,185 girls ages 9 to 10, found that girls who had high levels of potassium had lower blood pressure throughout adolescence than girls who were deficient in the mineral.

Experts suggest an intake of 4,700 milligrams of potassium daily. Citrus fruits, bananas, potatoes, kale, avocados, and fish are rich sources of potassium.