Eating pistachio nuts as part of a healthy diet may offer more health benefits than originally believed. A new study published in the Journal of Nutrition has found that the nuts can increase the levels of antioxidants in the blood.

Researchers conducted a controlled feeding experiment in which they provided participants with all of their food to test the effects of pistachios on antioxidant levels when added to a heart healthy moderate-fat diet.

The participants began the study by eating a typical American diet for two weeks. They then tested three cholesterol-lowering diets for four weeks each with about a two-week break between each diet. Two of the cholesterol-lowering diets included 10 and 20 percent of energy provided by pistachio nuts.

They found that both pistachio diets produced higher blood serum levels of antioxidants including beta-carotene, lutein and gamma-tocopherol than the typical American diet.

In addition, the pistachio diets were associated with lower oxidized low-density lipoproteins (LDL) concentrations in the blood. LDLs are implicated in inflammation and plaque buildup inside blood vessels.

"Our results suggest that a heart-healthy diet including pistachios contributes to a decrease in serum oxidized-LDL levels, in part through cholesterol lowering, and also due to an added benefit of the antioxidants in the pistachios," said researcher and Penn State nutrition professor Penny Kris-Etherton.