Pistachios help reduce stress of everyday life
Research has confirmed that eating pistachios may reduce the body’s response to stress. A Penn State study has shown that elevated reactions to stressors can be reduced by the inclusion of pistachios in the daily diet.
“A ten-year follow-up study of young men showed that those who had larger cardiovascular responses to stress in the lab, were more likely to contract hypertension later in life,” says Dr. Sheila G. West, associate professor of biobehavioral health. “Elevated reactions to stressors are partly genetic, but can be changed by diet and exercise. Lifestyle changes can make the biological reactions to stress smaller.”
A randomised controlled study examiniming the effects of pistachios on participants who had high cholesterol, but normal blood pressure. They used a randomized, crossover controlled feeding study plan. All three diets included an equal number of calories.
After a two-week run-in diet containing 35 percent fat and 11 percent saturated fats, each test diet lasted for four weeks during which time participants consumed only foods supplied by the study.
The 3 diets were: a standard heart healthy diet with 25 percent fat and 8 percent saturated fat, a diet containing 1.5 ounces of pistachios with 30 percent total fat and 8 percent saturated fat, and a diet containing 3 ounces of pistachios containing 34 percent fat and 8 percent saturated fat.
At the end of each four-week diet regime, the researchers measured blood pressure and total peripheral vascular resistance at rest and during two stress tests, one physiological and the other physical.
The physical test consisted of putting one foot in a bucket of ice water for 2.5 minutes. The psychological test asked participants to listen to two numbers, add them in their head and say the answer. Then they were asked to pay attention to another number and add it to the second number they heard, not the original sum.
“The ice water is a stimulus for the sympathetic nervous system, but it is very different form the stressors we encounter every day,” says West. “We also wanted to see if the reaction occurred when the stress was nonphysical, so we used the math test.”
The researchers found that both pistachio containing diets reduced the stress effects on blood pressure, but that the 1.5 ounce pistachio diet reduced systolic blood pressure by 4.8 millimeters of mercury while the 3-ounce pistachio diet only reduced systolic blood pressure by 2.4 millimeters of mercury. The diets had no effect on normal, resting blood pressure.
When the researchers examined total peripheral vascular resistance, it was clear that the 3-ounce diet led to greater relaxation of arteries. Because the body strongly controls blood pressure, rather than allowing blood pressure to drop further, the heart compensated by pumping more forcefully.
“The relaxation of blood vessels after the 3-ounce pistachio diet likely reduced the workload on the heart,” says West. “This pattern of change would be beneficial if it is maintained long term. It is possible that other foods that are high in unsaturated fat and antioxidants would have a similar effect.”