Eating pistachio nuts could keep heart disease at bay, says a study.

One of the oldest edible nuts on the planet, the pistachio nut is believed to have originated in the Middle East where it grew wild for thousands of years. The nuts are now available across the globe in roasted, salted, shelled and unsalted forms.

Like all nuts, pistachios are an excellent source of protein. They are thought to be rich in nutrients that appear to lower cholesterol and keep arteries healthy, reported the online edition of Daily Mail.

Penny Kris-Etherton and other researchers at the Pennsylvania State University asked volunteers to supplement a low fat diet with pistachios. Some ate 1.5 ounces of the nut a day, while others had double that amount, either alone as a snack or incorporating them into cereal, muffins and pesto sauce. A third group did not eat any pistachios.

After just a month, cholesterol levels were significantly lower among the pistachio eaters. Those who ate the most nuts experienced the biggest decrease in cholesterol, the researchers said.

A handful or two of pistachio nuts a day could keep heart disease at bay, the study suggests.

'Our study has shown that pistachios, eaten with a healthy heart diet, may decrease a person's cardiovascular disease risk profile,' Etherton said.

Pistachios are rich in an antioxidant called lutein, usually found in green leafy vegetables and brightly coloured fruit. Present at higher levels in the pistachio than other nuts, lutein helps prevent cholesterol from clogging up arteries.

Experts say it is best to eat unsalted rather than salted pistachios as too much salt can raise blood pressure. However, both types should have the same effect on cholesterol.