May 20, 2010 -- Long a staple of diets in the Mideast and around the Mediterranean, pistachio nuts may reduce the risk of cardiovascular disease, in part by decreasing cholesterol levels, a new study says.
Researchers say that pistachios are packed with antioxidants and are rich in several vitamins and minerals, such as selenium and iron, and also have healthy fats.
Penny Kris-Etherton, PhD, ND, of Pennsylvania State University’s Department of Nutritional Sciences, and colleagues, recruited 10 men and 18 women, all healthy nonsmokers, to eat the nuts.
They found that eating pistachios increased antioxidant levels in adults with high cholesterol.
“Our previous study showed the benefits of pistachios in lowering lipids and liproproteins, which are a risk factor for heart disease,” Kris-Etherton, a professor of nutrition, says in a news release. “This new study shows an additional effect of pistachios, so now there are multiple health benefits of eating pistachios.”
The little morsels also are high in antioxidants lutein, beta-carotene, and gamma-tocopherol, compared to other nuts. Beta-carotene is the precursor to vitamin A. Gamma-tocopherol is a form of vitamin E. Lutein is found in dark green leafy vegetables and is important in vision and skin health.
The Benefits of Pistachios
The researchers say antioxidants are of interest because oxidized low-density lipoproteins, known as LDL or “bad” cholesterol, have been implicated in inflammation and plaque buildup inside blood vessels.
Antioxidants should prevent LDL from oxidizing, migrating into the blood vessel walls, and causing inflammation, a Penn State news release says.
“Currently, studies on antioxidants do not show major benefits,” Kris-Etherton says. “Maybe we are not studying people long enough. Maybe there is something in the food that travels with the antioxidants. The antioxidant story is very disappointing to the scientific community.”
That’s the case because studies on specific antioxidants have not shown health benefits. However, she says epidemiological studies do seem to suggest benefits.
She and her research team conducted a randomized, controlled feeding experiment to test the effects of eating pistachios on antioxidant levels when added to a healthy diet.
The participants began by eating a diet of 35% total fat and 11% saturated fat for two weeks -- what the scientists described as typically American. Later, they tested three diets for four weeks each, with about a two-week break between each one. The diets included one with no pistachios and about 25% total fat and 8% saturated fat, a diet with 10% of calories from pistachios, and a diet with 20% of calories from pistachios.
The diets with pistachios produced higher blood levels of beta-carotene, lutein, and gamma-tocopherol than the diet without pistachios. The pistachio-enriched diets also produced lower oxidized concentrations of LDL cholesterol.
The results, Kris-Etherton says, 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.”
The study is published in the June 2010 issue of The Journal of Nutrition.