A handful of pistachios may lower cholesterol and provide the
antioxidants usually found in leafy green vegetables and brightly
colored fruit, according to a team of researchers.
"Pistachio amounts of 1.5 ounces and 3 ounces - one to two handfuls
- reduced risk for cardiovascular disease by significantly reducing
LDL cholesterol levels and the higher dose significantly reduced
lipoprotein ratios," says Sarah K. Gebauer, graduate student in
integrative biosciences, Penn State, to attendees at the Experimental
Biology meeting today (April 30) in Washington, D.C.
The researchers conducted a randomized, crossover design, controlled
feeding experiment to test the effects of pistachios added to
a heart healthy moderate-fat diet on cardiovascular disease risk
factors. Controlled feeding experiments provide all the food eaten
by study subjects for the duration of the study segment.
Participants began the study by eating an Average American Diet
consisting of 35 percent total fat and 11 percent saturated fat
for two weeks. They then tested three diets for four weeks each
with a two-week break between each diet.
All three diets were variations on the Step I Diet, a cholesterol-lowering
diet in general use. The diets included a Step I Diet without
pistachios which had 25 percent total fat and 8 percent saturated
fat; a Step I Diet including 1.5 ounces of pistachios per day
which had 30 percent total fat and 8 percent saturated fat, and
a Step I Diet including three ounces of pistachios per day which
had 34 percent total fat and 8 percent saturated fat. The researchers
added pistachios into the diets by including about half the amount
of pistachios as a snack and by incorporating the rest into such
foods as pistachio muffins, granola and pistachio pesto.
"We had really good compliance and participants were generally
pleased with the diets," says Gebauer.
Standard blood tests determined the various cholesterol levels
in the participant's blood after each diet. Researchers found
that 3 ounces of pistachios reduced the amounts of total cholesterol
in the blood by 8.4 percent and low-density lipoprotein (LDL),
the so-called bad cholesterol, by 11.6 percent. The study also
found that non-high density lipoproteins (non-HDL) decreased by
11.2 percent. Non-HDL levels are considered reliable predictors
of cardiovascular disease risk.
The three-ounce pistachio diet also decreased the ratios of total
cholesterol to HDL, LDL to HDL and non-HDL to HDL and apolipoprotein
B, which are all measures of cardiovascular disease risk. "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,"
In addition, during this study researchers, researchers looked
at the effects of these diets on oxidized LDL and on antioxidants
in the blood.
"We were trying to see if the increased levels of antioxidants
provided by pistachios could reduce inflammation and oxidation,"
says Gebauer. Pistachios contain more lutein, - normally found
in dark leafy vegetables -- beta carotene - a precursor to vitamin
A - and gamma tocopherol - the major form of vitamin E - than
other nuts. It is oxidized LDL and other lipproteins that contribute
to plaque formation in arteries.
The researchers reported that both the 1.5 and 3 ounce pistachio
diets reduced oxidized LDL compared with the baseline diet. Pistachio-enriched
diets also resulted in significantly higher levels of lutein in
the blood. The increased lutein from the 3-ounce pistachio diet
correlated with a reduction in oxidized LDL which may indicate
that the lutein in pistachio nuts improves the risk of cardiovascular
disease by reducing serum oxidized LDL.
"Our study has shown that pistachios, eaten with a heart healthy
diet, may decrease a person's CVD risk profile," says Dr. Penny
Kris-Etherton, distinguished professor of nutrition and primary
investigator of the study.