Managing cardiovascular risk factors is important in reducing vascular complications in type 2 diabetes, even in individuals who have obtained glycemic control. The cardiovascular complications of diabetes are life-threatening and disabling. Nut consumption is linked with reduced cardiovascular risk however, there is mixed evidence about the effect of nuts on blood pressure (BP), and limited research on the underlying hemodynamics.
Dr. Shelia G. West, PhD, professor of biobehavioral health, Director, Vascular Health Interventions Laboratory / Stress and Nutrition Research Program at the Pennsylvania State University and colleagues examined the effect of pistachio consumption on responses to standardized stress tasks in patients with well-controlled Type 2 diabetes who were otherwise healthy.
The study included 30 adult participants aged 40 to 74 years with type 2 diabetes. Participants consumed a typical American diet containing 36% fat and 12% saturated fat.
After the two weeks, participants were randomized to one of two diet tests for a period of four weeks in which during that time participants only consumed food which had been supplied by the study.
The two diets in the tests were a standardized heart healthy diet that included 27% fat and 7% saturated fat and included two servings of pistachios a day ( about 3 ounces or 20% of calories from pistachio nuts) The other diet; pistachio diet included 33% and 7% saturated fat.
The average participant consumed around 150 pistachios daily, with half being salt and half being unsalted.
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 (cold water challenge and confusing mental arithmetic test). Peripheral vascular resistance is a resistance to the flow of blood determined by the tone of the vascular musculature and the diameter of the blood vessels. It is responsible for blood pressure when coupled with stroke volume.
According to Dr. West “This cold stressor produces a large vascular constriction response in most people.” "In comparison with a low fat diet, the pistachio diet blunted that vascular response to stress."
The same pattern was seen when participants did the confusing mental arithmetic test.
"Our participants still felt frustrated and angry during the math test," said Dr. West. "The pistachio diet reduced their bodies' responses to stress, but nuts are not a cure for the emotional distress that we feel in our daily lives."
Dr. Katherine A. Sauder, PhD, Department of Biobehavioral Health, The Pennsylvania State University, added "As in our last study of pistachios, we did not see lower blood pressure in the laboratory setting with this dose of nuts. However, we were surprised and pleased to see that 24-hour ambulatory blood pressure was lower after the pistachio diet."
The results revealed that the pistachio diet significantly reduced total peripheral resistance (2.9%), increased cardiac output (2.3%), and improved some measures of heart rate variability. a measure of how well the nervous system controls heart function. Systolic ambulatory blood pressure was significantly reduced by 3.5±2.2 mm Hg following the pistachio diet. The greatest reduction in blood pressure was during sleep with the average blood pressure being reduced by 4%.
In closing Dr. West commented "If sustained with longer term treatment, these improvements in sleep blood pressure, vascular response to stress and vagal control of the heart could reduce risk of heart disease in this high risk group.
This study is published in the "Journal of the American Heart Association, Hypertension