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To Lower Cholesterol,
You Should Eat Pistachios
 Date:
1 May 07
One or two handfuls of the nuts can make a big enough
difference to lower the risk of heart disease, say
scientists.
Volunteers who ate three ounces of pistachios a day for one
month lowered their total blood cholesterol by 8.4%.
Crucially, levels of "bad" cholesterol, low-density
lipoprotein (LDL), went down by 11.6%.
The balance between LDL and "good" cholesterol, high-density
lipoprotein (HDL), was also changed. Participants on the
pistachio diet had less LDL relative to HDL after four
weeks.
HDL is protective rather than harmful and lower ratios
between the two kinds of cholesterol are considered
healthier.
The volunteers were given pistachios as a daily snack and
also had them incorporated into other foods such as muffins
and pesto sauce.
Researcher Sarah Gebauer, from Pennsylvania State University
in the US, said: "Pistachio amounts of 1.5 ounces and three
ounces - one to two handfuls - reduced risk for
cardiovascular disease by significantly reducing LDL
cholesterol levels and the higher dose significantly reduced
lipoprotein ratios.
"We were pleased to see a difference between the two doses
of pistachios for the lipoprotein ratios because it would
appear that pistachios are causing the effect and that they
act in a dose dependent way."
At the start of the study participants ate an average
American diet consisting of 35% total fat and 11% saturated
fat for two weeks. They were then put onto one of three
different diets, all variants of a normal
cholesterol-lowering low-fat diet. One included no
pistachios, the second 1.5 ounces of pistachios a day, and
the third three ounces of pistachios a day.
Lead researcher Dr Penny Kris-Etherton said: "Our study
has shown that pistachios, eaten with a healthy heart diet,
may decrease a person's cardiovascular disease risk
profile."
Pistachios are rich in an antioxidant called lutein,
usually found in green leafy vegetables and brightly colored
fruit.
Present at higher levels in the pistachio than other
nuts, lutein helps prevent cholesterol from clogging up
arteries.
Experts say it is best to eat unsalted rather than
salted pistachios as too much salt can raise blood pressure.
However, both types should have the same effect on
cholesterol according to the research.
A further report from
ZeeNews
provided these additional details:
"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."
West and her colleagues inspected the effects of pistachios
on uniform stressors on participants who had high
cholesterol, but normal blood pressure. They used a
randomized, crossover controlled feeding study plan and all
three diets included 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 researchers reported the results of this study at
Experimental Biology 2007 on April 30 in Washington, D.C.
The diets given to the participants included a Step I Diet,
a standard heart healthy diet with 25 percent fat and 8
percent saturated fat.
The Step I Diet incorporated 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.
The two tests consisted of a physical test and a
psychological test. 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 sum they spoke.
"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
abridged 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 we only look at blood pressure, these results are
confusing," says West. "If it is the pistachios, why is it
not dose related?"
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."
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