The study, published in The Journal of the American College of Nutrition, and conducted by James N. Cooper of George Mason University and Michael J. Sheridan of Inova Fairfax Hospital, looked at individuals with relatively high cholesterol who replaced high-fat snacks with pistachio nuts on a daily basis. When on a diet that involved getting 15 per cent of daily calorie intake from pistachios for four weeks -- which means snacking on one to two handfuls a day -- subjects were found to improve blood lipid levels.

"These results are exciting because the research indicates that adding pistachios to the daily diet can help protect the heart without a dramatic dietary lifestyle change," Cooper said in a statement. "This research challenges the previously held belief that a low-fat diet is best for heart health."

The majority of the fat in pistachios is considered a "good" fat, monounsaturated fat, the kind that lowers blood pressure.