Pistachio nuts, eaten as part of a healthy diet, can increase the levels of antioxidants in the blood of adults with high cholesterol, according to a new study by an international team of researchers.
"Our previous study showed the benefits of pistachios in lowering lipids and lipoproteins, which are a risk factor for heart disease," said Penny Kris-Etherton, Penn State professor of nutrition. "This new study shows an additional effect of pistachios so now there are multiple health benefits of eating pistachios."
The researchers note in the May 20 issue of the Journal of Nutrition that "pistachios are high in lutein, beta-carotene and gamma-tocopherol relative to other nuts; however, studies of the effects of pistachios on oxidative status are lacking."
Beta-carotene is the precursor to vitamin A and gamma-tocopherol is a common form of vitamin E. Lutein is found in dark green leafy vegetables and is important in vision and healthy skin. All three compounds are oil soluble vitamins.
Antioxidants are of interest because oxidized low-density lipoproteins (LDL) are implicated in inflammation and plaque buildup inside blood vessels. Antioxidants should prevent LDLs from oxidizing, migrating into the blood vessel walls and causing inflammation.
"Currently, studies on antioxidants do not show major benefits," said Kris-Etherton. "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."
The reason for the disappointment is that studies on specific antioxidants currently do not show health benefits, but epidemiological studies seem to indicate benefits. Many people feel that we have not figured out antioxidants yet, said Kris-Etherton.
If antioxidants are important, then pistachios fit the bill as antioxidant-laden food.