Eating pistachios may reduce the body's response to the stresses of everyday life among people with type 2 diabetes, according to a recent study.

Researchers from Penn State University found that two servings of pistachios per day lowered vascular constriction during stress and improved neural control of the heart.

"Although nuts are high in fat, they contain good fats, fiber, potassium and antioxidants," said researcher Sheila G. West, professor of biobehavioral health and nutritional sciences. "Given the high risk of heart disease in people with diabetes, nuts are an important component of a heart healthy diet in this population."

For the study, researchers investigated the effects of pistachios on responses to standardized stress tasks in patients with well-controlled Type 2 diabetes who were otherwise healthy. They used a randomized, crossover study design in which all meals were provided. Each of the diets contained the same number of calories.

After two weeks on the typical American diet -- containing 36 percent fat and 12 percent saturated fats -- participants were randomized to one of two test diets - a standard heart-healthy diet and a diet containing two servings per day of pistachios. During the four-week test diets, participants ate only food supplied by the study.

At the end of each four-week diet period, the researchers measured blood pressure and total peripheral vascular resistance at rest and during two stress tests -- a cold water challenge and a confusing mental arithmetic test.

"After the pistachio diet, blood vessels remained more relaxed and open during the stress tests," West said.

During the first stress test, they found that the pistachio diet lowered vascular constriction during stress. When arteries are dilated, the load on the heart is reduced. The physical challenge involved immersing one hand into icy water for two minutes.

"This cold stressor produces a large vascular constriction response in most people," West said. "In comparison with a low fat diet, the pistachio diet blunted that vascular response to stress."

The same pattern was seen when participants engaged in a challenging and confusing mental arithmetic task.

The researchers also recorded improvements in heart rate variability, a measure of how well the nervous system controls heart function. These data indicate that pistachios increased the activity of the vagus nerve, an important part of the parasympathetic nervous system that can be damaged with diabetes.

The findings were recently published in the Journal of the American Heart Association.