Researchers Link Pistachios to Lower Blood Pressure

29 May 2015 --- Pistachio nuts, singled out among other nuts, seem to have the strongest effect on reducing blood pressure in adults. This is according to a recent review and scientific analysis of 21 clinical trials, all carried out between 1958 and 2013.

The review appears online in The American Journal of Clinical Nutrition, a publication of the American Society for Nutrition.

Hypertension contributes to more than 7 million deaths annually worldwide attributed to cardiovascular disease. While numerous studies have shown eating nuts provides cardiovascular benefits to healthy as well as to high risk individuals and those with type 2 diabetes, the authors state that, to their knowledge, no systematic review and meta-analysis of published randomized controlled trials has been conducted to assess the effect of nut consumption on blood pressure.

The researchers concluded that nut consumption can reduce blood pressure and particularly systolic blood pressure. Of the nuts studied, pistachios seemed to have the strongest effect in reducing both systolic and diastolic blood pressure.

This review and analysis included subjects with and without type 2 diabetes, recognizing the consumption of nuts could affect blood pressure in people with or without type 2 diabetes in different ways. Subgroup analyses based on the type of nut consumed suggest that pistachios significantly reduce both systolic and diastolic blood pressure, where mixed nuts reduce only diastolic blood pressure. When those with type 2 diabetes were removed from the analysis, only pistachios decreased systolic blood pressure as well.

Databases were searched for randomized clinical trials (RCTs) that reported the effect of consuming single or mixed nuts including walnuts, almonds, pistachios, cashews, hazelnuts, macadamias, pecans, peanuts and soy nuts on systolic blood pressure or diastolic blood pressure. Twenty-one trials were selected which studied 1,652 adults, ages 18-86 years.

The study points out that pistachios contain monounsaturated fatty acids and high amounts of phytosterols which may have beneficial effects on blood pressure and other nutrient qualities that lead to a reduction in oxidized LDL cholesterol and an improved antioxidant status. The study conclusion says although some medications and exercise appear to be effective in reducing blood pressure, healthy diets that include tree nuts may help to enhance their effectiveness and even result in reducing the dosage of hypertension medications.

The review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and was registered in an international prospective register of systematic reviews. Meta-analysis consists of applying statistical methods for combining the findings from different independent but similar studies. Reviewers followed strict criteria for including or excluding studies and then pooled and tested the data for sources of agreement or disagreement.

Dr. Arianna Carughi, nutrition consultant to American Pistachio Growers comments, “This study shows the benefits that pistachios can have on an important risk factor for cardiovascular disease: high blood pressure.” Dr. Carughi continues, “It supports the recommendations to include nuts, particularly pistachios, as part of a healthy diet for the prevention of cardiovascular disease.”

This project was conducted by researchers with the Isfahan Cardiovascular Research Center, the Hypertension Research Center, Isfahan Cardiovascular Research Institute, the Food Security Research Center, Isfahan University of Medical Sciences and the Department of Nutrition, Faculty of Health, Shahid Sadoughi University of Medical Sciences, Iran; the Human Nutrition Unit, Department of Biochemistry and Biotechnology, IISPV, School of Medicine, Rovira i Virgili University, and CIBER Obesity and Nutrition, Reus, Spain; and Cardiology Division, Department of Medicine, University of British Columbia, Vancouver, Canada.