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Deep Dive: Dietary Approaches to Stop Hypertension (DASH) Diet and Blood Pressure

The DASH diet lowers blood pressure to roughly the same extent regardless of your baseline pressure. And every little bit helps.

Study under review: Reduction in Adults with and without Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Introduction

Hypertension, defined by the American College of Cardiology and the American Heart Association as blood pressure greater than or equal to 130/80 milligrams of mercury (mmHg), puts people at risk of heart disease and stroke, which are leading causes of death in the U.S. Even small reductions in blood pressure can decrease the risk[1] of coronary events, stroke, and death. The American Heart Association’s recommendations for management of hypertension include both non-pharmacological strategies and the use of blood pressure-lowering medication. One of the non-pharmacological strategies is adoption of a heart-healthy diet, such as the Dietary Approaches to Stop Hypertension (DASH) diet.

The DASH diet originated in 1997 from the results of a clinical trial[2] that examined the effects of the eponymous dietary pattern. This controlled feeding trial examined three diets, one of which (the DASH diet) was rich in fruits, vegetables, and low-fat dairy. The DASH diet reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) in comparison to the control diet and fruit and vegetable diet. Perhaps unexpectedly, the original DASH diet did not include sodium restriction[3]. The current recommendation included in the DASH diet includes a goal of no more than 2,300 milligrams of salt per day, preferably less than 1,500 milligrams per day. Subsequently, many trials[4] have shown that the DASH diet improves SBP and DBP.

The existing body of clinical trials that examined the blood pressure-lowering effects of the DASH diet differ in regard to methodology (e.g., amount of calories and sodium) and clinical characteristics of the participants (e.g., normotensive compared to hypertensive or normal weight compared to overweight). The differences in these studies mean that taking their average may suggest misleading conclusions. The goal of this meta-analysis was to assess the effect of the DASH diet on blood pressure in people with and without hypertension while accounting for these potential effect modifiers.

Hypertension is a significant cause of morbidity and mortality due to its contribution to heart disease, stroke, and other adverse health outcomes. The DASH diet, a dietary pattern that emphasizes fruits and vegetables, plant-based proteins such as beans and nuts, lower-fat dairy products, and unsaturated fats like olive oil, while encouraging adherents to avoid fatty red meats, processed meats, and refined carbohydrates alongside limiting sodium to less than 2,300 milligrams per day has been shown to decrease blood pressure. The study under review was a meta-analysis examining the effect of the DASH diet on changes in blood pressure in participants with normal blood pressure and high blood pressure.

What was studied?

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Other Articles in Issue #69 (July 2020)