Potatoes have emerged as an unlikely superfood after a study showed they can reduce blood pressure.
US scientists fed 18 volunteers six to eight potatoes twice a day and found that after a month their average blood pressure readings had improved.
Systolic blood pressure, the "upper" reading when blood is pumped with each beat of the heart, was down by 3.5 per cent.
At the same time, the diastolic "lower" reading, showing the pressure between beats when blood vessels are relaxed, decreased by 4.3 per cent.
Most of the patients were overweight or obese and already taking drugs for high blood pressure, yet the potatoes still appeared to have an effect.
"The potato, more than perhaps any other vegetable, has an undeserved bad reputation that has led many health-conscious people to ban them from their diet," said lead researcher Dr Joe Vinson, from the University of Scranton in
Pennsylvania, US.
"Mention 'potato' and people think 'fattening, high-carbs, empty calories'. In reality, when prepared without frying and served without butter, margarine or sour cream, one potato has only 110 calories and dozens of healthful phytochemicals and vitamins.
"We hope our research helps to remake the potato's popular nutritional image."
For the study, the researchers used purple potatoes that were cooked in a microwave in their jackets without oil.
Purple potatoes were chosen because colour pigments in fruits and vegetables are especially rich in beneficial chemicals. But the scientists believe red-skinned or white potatoes may have similar effects.
Dr Vinson presented the findings at the annual meeting of the American Chemical Society in Denver.
He said previous studies had identified substances in potatoes which acted in the same way as ACE inhibitors, widely-used drugs for controlling high blood pressure.
Unfortunately for chip fans, high cooking temperatures destroy most of the healthy chemicals in potatoes, leaving mainly starch, fat and minerals.
Microwaving appears to be the best way to preserve potato nutrients, according to Dr Vinson.
PA