A Pennsylvania State University study published online this month in Hypertension, an American Heart Association Journal, reveals that including pistachios in a healthy diet may positively reduce the body’s response to the stresses of everyday life.

Adults with elevated cholesterol were enrolled in a randomized, controlled clinical trial comparing diets containing pistachios to a low fat diet. The results show that a healthy diet supplemented with pistachios helps decrease systolic blood pressure, peripheral vascular resistance and heart rate during acute stress. Cardiovascular responses were measured while participants engaged in a challenging mental arithmetic test and again as they immersed their foot in cold water.

The study conducted at Pennsylvania State University by Drs. Sheila G. West and Penny M. Kris-Etherton and colleagues examined how diets containing pistachios (one-and-a-half and three ounces per day) versus a low-fat diet without pistachios, affect responses to stress on subjects with elevated LDL cholesterol, but normal blood pressure. This study is the first to show that including both salted and unsalted pistachios in a healthy diet helps reduce blood pressure and lessen the vascular load on the heart.

The people in the study were healthy, non-smoking men and women with elevated LDL cholesterol (commonly regarded as bad cholesterol) but normal blood pressure. All of the meals were provided and calorie levels were customized to maintain body weight. Pistachios were substituted for other foods in the diet to prevent weight gain. Participants followed three different diets – one low fat diet (25 percent fat ) without pistachios, and two with different levels of pistachios (approximately 1.5 oz or 10 percent of calories from pistachios and 3.0 oz or (20 percent of calories from pistachios). The pistachio diets contained higher amounts of potassium, healthy fats and protein. All diets were rich in fruit, vegetables, lean meats, and whole grains, consistent with current food-based dietary recommendations. Participant demographics and the diet design have been published previously.(2)

“Daily events, such as work stress, a tight deadline, or public speaking can increase blood pressure, and we know that we can’t avoid all of the stressors in our lives. These results are significant because they show that physiological responses to stress are affected by the foods we eat,” stated Sheila West, Ph.D., Associate Professor of Biobehavioral Health and the study’s lead author. Dr. West continues, “These changes in blood pressure occurred even though self-reported mood, anxiety, and tension were not changed.”