Effects of Sodium Reduction and the DASH Diet in Relation to Baseline Blood Pressure

Abstract

Background: Both sodium reduction and the DASH (Dietary Approaches to Stop Hypertension) diet, a diet rich in fruits, vegetables, and low-fat dairy products, and reduced in saturated fat and cholesterol, lower blood pressure. The separate and combined effects of these dietary interventions by baseline blood pressure (BP) has not been reported.

Objectives: The authors compared the effects of low versus high sodium, DASH versus control, and both (low sodium-DASH vs. high sodium-control diets) on systolic blood pressure (SBP) by baseline BP.

Methods: In the DASH-Sodium (Dietary Patterns, Sodium Intake and Blood Pressure) trial, adults with pre- or stage 1 hypertension and not using antihypertensive medications, were randomized to either DASH or a control diet. On either diet, participants were fed each of 3 sodium levels (50, 100, and 150 mmol/day at 2,100 kcal) in random order over 4 weeks separated by 5-day breaks. Strata of baseline SBP were <130, 130 to 139, 140 to 149, and ≥150 mm Hg.

Results: Of 412 participants, 57% were women, and 57% were black; mean age was 48 years, and mean SBP/diastolic BP was 135/86 mm Hg. In the context of the control diet, reducing sodium (from high to low) was associated with mean SBP differences of -3.20, -8.56, -8.99, and -7.04 mm Hg across the respective baseline SBP strata listed (p for trend = 0.004). In the context of high sodium, consuming the DASH compared with the control diet was associated with mean SBP differences of -4.5, -4.3, -4.7, and -10.6 mm Hg, respectively (p for trend = 0.66). The combined effects of the low sodium-DASH diet versus the high sodium-control diet on SBP were -5.3, -7.5, -9.7, and -20.8 mm Hg, respectively (p for trend <0.001).

Conclusions: The combination of reduced sodium intake and the DASH diet lowered SBP throughout the range of pre- and stage 1 hypertension, with progressively greater reductions at higher levels of baseline SBP. SBP reductions in adults with the highest levels of SBP (≥150 mm Hg) were striking and reinforce the importance of both sodium reduction and the DASH diet in this high-risk group. Further research is needed to determine the effects of these interventions among adults with SBP ≥160 mm Hg. (Dietary Patterns, Sodium Intake and Blood Pressure [DASH-Sodium]; NCT00000608).

Keywords: DASH; blood pressure; diet; sodium; trial.

Figure 1. The Combined Effects of Low Sodium and the DASH Diet according to Blood Pressure

Mean end of period systolic blood pressure measurements (mmHg) by strata of (A) baseline systolic blood pressure (<130, 130-139, 140-149, ≥150 mmHg) or (B) baseline diastolic blood pressure (<80, 80-84, 85-89, ≥90 mmHg). Mean blood pressure values are presented by (1) the high sodium-control diet (circle) or (2) the low sodium-DASH diet (diamond). Differences between diets were determined using linear regression comparing baseline changes in systolic or diastolic blood pressure adjusted for age, female sex, black race, and baseline body mass index. Bars represent 95% confidence intervals. SBP represents systolic blood pressure. DBP represents diastolic blood pressure.

Central Illustration. The Blood Pressure (BP) Effects of the DASH Diet

Sodium reduction, alone or combined, compared to average BP effects of anti-hypertensive drug therapies and the FDA requirement for new antihypertensive drugs. Estimates for anti-hypertensive drug classes are taken from Manisty et al 2013. The FDA requirement for new antihypertensive drugs is take from a committee meeting of the Center for Drug Evaluation and Research (2014)