Study leader Dr. Penny Kris-Etherton conducted a randomized, crossover, controlled study of 28 healthy men and women ages 30 to 70 with slightly-elevated cholesterol levels -- similar to cholesterol levels of the general population. The researchers tested three cholesterol-lowering diets, one without pistachio consumption, one with 1.5 ounces of pistachios and a third with 3 ounces. All diets provided the same amount of saturated fat and cholesterol, but different amounts of unsaturated fat delivered by pistachios. Participants were fed the same diet for two weeks.

Both the 1.5- and 3-ounce pistachio diets resulted in reduction of total cholesterol and low density lipoprotein cholesterol, or the "bad" cholesterol, the study said.

In addition, the pistachios significantly reduced inflammation at the cellular level, Kris-Etherton said.

"Reducing inflammation at the cellular level is an important finding as it may be a more specific marker of inflammatory status than blood markers, which are general indicators of inflammation in the body," Dr. Sarah Gebauer of Pennsylvania State University said.

The findings are being presented at the Experimental Biology 2008 conference in San Diego.