PISTACHIOS MAY LOWER VASCULAR RESPONSE TO STRESS IN TYPE 2 DIABETES
Among people with type 2 diabetes, eating
pistachios may reduce the body's response to the stresses of everyday life,
according to Penn State researchers.
In adults with
diabetes, two servings of pistachios per day lowered vascular constriction
during stress and improved neural control of the heart," said Sheila G.
West, professor of biobehavioral health and nutritional sciences.
"Although nuts are high in fat, they contain good fats, fiber, potassium
and antioxidants. Given the high risk of heart disease in people with diabetes,
nuts are an important component of a heart healthy diet in this
population."
West and her
colleagues 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. During the
four-week test diets, participants ate only food supplied by the study. The
researchers reported the results of this study in a recent issue of the Journal
of the American Heart Association.
Test diets included a
standard heart-healthy diet -- 27 percent fat and 7 percent saturated fat --
and a diet containing two servings per day of pistachios -- about 3 ounces or
20 percent of calories from pistachio nuts. The typical research participant
consumed about 150 pistachio nuts per day. The pistachio diet contained 33
percent fat and 7 percent saturated fat. Half of the nuts consumed each day
were salted and half were 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 -- 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.
Although laboratory
measurements of blood pressure were not affected by pistachios, real-world
measures of blood pressure (measured by an automated monitor) were
significantly lower after the pistachio diet. Katherine A. Sauder, former
graduate student in biobehavioral health, conducted these measurements.
"We found that
systolic blood pressure during sleep was particularly affected by
pistachios," she said. "Average sleep blood pressure was reduced by
about 4 points and this would be expected to lower workload on the heart."
The researchers 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,"
said West. "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.
"Our participants
still felt frustrated and angry during the math test," West noted.
"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."
Sauder 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 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
"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," West said.
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