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Title: Clinical trial of the effects of dietary patterns on blood pressure

Authors: Appel L ,  Moore T, Obarzanek, et al.

Reference: N Engl J Med 1997;336:1117-24

Reviewer: James Orford

Purpose of study: To investigate the effects of dietary patterns on blood pressure.

Location of study: USA

Methods:  After three weeks on a control typical American diet, patients were randomly assigned to receive the control diet, a diet rich in fruits and vegetables that provided potassium and magnesium at levels close to the 75th percentile of U.S. consumption, along with high amounts of fiber; or to a "combination" diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat.

Results: The combination diet reduced systolic blood pressure by 5.5 mm Hg and diastolic blood pressure by 3.0 mm Hg as compared to the control diet (P<0.001). The reductions with the fruits and vegetables diet were 2.8 mm Hg (P<0.001) and 1.1 mm Hg greater than with the control diet (P<0.07). Subjects with hypertension had greater reductions in blood pressure than subjects without hypertension.

Discussion: The trial demonstrated that certain dietary patterns can favorably affect blood pressure in adults with average systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80 to 95 mm Hg. Specifically, a diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat lowered systolic blood pressure by 5.5 mm Hg and diastolic blood pressure by 3.0 mm Hg more than a control diet. A diet rich in fruits and vegetables also reduced blood pressure, but to a lesser extent.

In patients with hypertension, the decrement in blood pressure with the combination diet is similar to that observed in trials of drug monotherapy for mild hypertension.

It is estimated that a population-wide reduction in systolic or diastolic blood pressure of the magnitude observed with the combination diet would reduce incident coronary heart disease by approximately 15% and stroke by approximately 27%.

Comments: Hypertension is a prevalent problem in both developed and developing countries. The adoption of a Western diet is a well-documented trend in developing countries. This study provides both statistically and clinically significant proof that a healthy diet high in fruits and vegetables and low in saturated fat reduces hypertension.  Of great relevance is the cost-effective nature of this simple intervention. The obvious difficulty is patient education in the face of overwhelming socio-cultural and financial.