Adding to a growing body of evidence, several new research studies continue to demonstrate that a diet incorporating a moderate amount of healthful monounsaturated fat, like the kind found in pistachios, is more effective in preventing heart disease than simply reducing overall fat intake.
At the April 30, 2007 Experimental Biology Conference in Washington, DC, Pennsylvania State University graduate student researcher Sarah K. Gebauer presented data showing that a handful of pistachios may lower cholesterol and provide the antioxidants usually found in leafy green vegetables and brightly colored fruit.
In the study, volunteers with high cholesterol levels were asked to supplement a low-fat diet with pistachios. Subjects ate three different diets for a four-week period. The diets consisted of 1.5 ounces of pistachios a day, three ounces of pistachios a day or a Step-1 diet without pistachios. After just a month, cholesterol levels were significantly lower among the pistachio eaters: three 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.
"Our study has shown that pistachios, eaten with a heart healthy diet, may decrease a person's CVD risk profile," added Penny Kris-Etherton, distinguished professor of nutrition and primary investigator of the study. "We were pleased to see a difference between the doses of pistachios for lipoprotein ratios because it would appear that pistachios are causing the effect and that they act in a dose dependent way," added Gebauer.
A four-week diet consisting of a daily dose of about two to three ounces of pistachios may offer protective benefits against cardiovascular disease, according to another study published in the Volume 26, Number 2 issue of the Journal of the American College of Nutrition.
The Inova Fairfax Hospital study found that in people with moderately high cholesterol levels, a daily diet consisting of 15% of calories from pistachios (about two to three ounces or one to two handfuls of kernels) over a four-week period favorably improved some blood lipid levels. Most likely, this is due to pistachios' content of healthful monounsaturated fat, according to lead researcher James N. Cooper, M.D. of George Mason University.
"This research challenges the previously-held belief that a low-fat diet is best for heart health. Studies now show that a diet with a moderate amount of healthful monounsaturated fat, like the kind found in pistachios, is a more effective way to prevent heart disease than reducing overall fat intake."
Thought to be rich in nutrients that reduce hardening of the arteries, pistachios may also protect against coronary heart disease through other mechanisms, one of which is arginine, according to Dr. Hu of Harvard's Department of Nutrition.
Eating pistachios may reduce the body's response to the everyday stresses of life, according to another study conducted at Pennsylvania State University, lowering the risk of developing hypertension. Dr. Sheila G. West, associate professor of biobehavioral health, investigated the effects of pistachio consumption on standardized stressors on persons who had high cholesterol, but normal blood pressure. West and her colleagues found that those who consumed 1.5 ounces of pistachios each day reduced the stress effects of systolic blood pressure by 4.8 millimeters of mercury, with no effect on normal, resting blood pressure.
Most of the fat in pistachios - almost 90% - is "good" or unsaturated fat, which can lower blood cholesterol along with risk of heart disease, when they replace saturated fats in the diet. Of all snack nuts, pistachios offer the highest level of phytosterols, and are a powerful source of fiber, both of which reduce the absorption of cholesterol from the diet.
Participants in the Penn State pistachio study showed no changes in blood pressure, body mass index or weight gain, further supporting previous studies that have also demonstrated no weight gain from the addition of pistachios to the daily diet. Nut consumption, in general, is associated with a lower body mass index.
A 1-oz serving of pistachios, with 160 calories, offers an excellent source of vitamin B6, copper and magnesium; and are a good source of fiber, thiamin and phosphorus making them a wise snack choice. For more information on these studies, visit www.pistachiohealth.com
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