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Consciousness of Blood Pressure Is Rising as Details About Possible Remedies Continue to Evolve: Pistachios May Reduce Risk for Hypertension


Pistachios May Reduce Risk for Hypertension

The beneficial effects of almonds and walnuts on cardiovascular disease have been studied extensively, but relatively little research has been carried out into the effects of pistachios on cardiovascular disease risk factors. Pistachios have been reported as having a beneficial effect on serum lipids, and in July 2003, the US Food and Drug Administration (FDA) approved a qualified health claim that can appear on packages:

Scientific evidence suggests but does not prove that eating 1.5 oz. per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.

Now researchers have reported that eating pistachios may help to prevent hypertension. The results of this study were presented on April 30 in Washington, DC, at Experimental Biology 2007, the combined annual meeting of the American Association of Anatomists; the American Physiological Society; and the American Societies for Biochemistry and Molecular Biology, Investigative Pathology, Nutrition, and Pharmacology and Experimental Therapeutics.[20]

Lead investigator Sheila G. West, PhD (Pennsylvania State University, University Park, Pennsylvania) explained that people who have larger cardiovascular responses to stress are believed to be at higher risk for development of cardiovascular syndromes, such as hypertension, later in life than those who have smaller responses. "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," she said.

According to the results of the randomized, controlled, crossover feeding study carried out by Dr. West and her colleagues (and supported by the California Pistachio Commission), adding pistachios to the diet appeared to reduce elevated reactions to stressors. A total of 28 hypercholesterolemic adults (10 men and 18 women) with normal blood pressure underwent a 2-week run-in period on a diet including 35% total fat and 11% saturated fatty acids (SFAs). The subjects were then fed 3 iso-energetic diets for 4 weeks. All 3 diets were followed the National Cholesterol Education Program (NCEP) Step I diet (< 30% of total energy from fat, < 10% of energy from saturated fat, and < 300 mg cholesterol per day) with or without pistachios:

Diet 1: Step I diet without pistachios (25% total fat, 8% SFAs);

Diet 2: Step I diet with 1.5 oz/day of pistachios (30% total fat, 8% SFAs);

Diet 3: Step I diet with 3.0 oz/day of pistachios (34% total fat, 8% SFAs).

At the end of each diet period, blood pressure and peripheral vascular resistance were measured at rest and during a math test and cold pressor test. Both pistachio diets significantly blunted the stress-induced blood pressure responses, but the effect was greater with the 1.5-oz pistachio diet than with the 3.0-oz diet (mean reduction in SBP: 4.7 mm Hg vs 2.4 mm Hg, respectively). Neither diet had any effect on normal resting blood pressure.

These results were confusing, Dr. West admitted, because if the pistachios caused the blood pressure-lowering effect, it would be expected to be dose-related. When the investigators looked at the effects on systemic hemodynamics, they found that the decreases in total peripheral vascular resistance and heart rate induced by the 3.0-oz pistachio diet were offset by increases in cardiac output. This shift in systemic hemodynamics would be expected to be beneficial if maintained long-term, by reducing cardiac workload, Dr. West said. "Our results suggest a novel, dose-dependent mechanism for the cardioprotective effects of pistachios," she suggested, adding that other foods that are high in unsaturated fat and antioxidants may have a similar effect. In a separate presentation at the conference, Dr. West's group reported that the 1.5-oz and 3.0-oz pistachio diets also appeared to improved lipid, lipoprotein, and apolipoprotein profiles, in a dose-dependent manner.[21]

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