Time Course of Change in Blood Pressure From Sodium Reduction and the DASH Diet

Abstract

Both sodium reduction and the Dietary Approaches to Stop Hypertension (DASH) diet lower blood pressure (BP); however, the patterns of their effects on BP over time are unknown. In the DASH-Sodium trial, adults with pre-/stage 1 hypertension, not using antihypertensive medications, were randomly assigned to either a typical American diet (control) or DASH. Within their assigned diet, participants randomly ate each of 3 sodium levels (50, 100, and 150 mmol/d, at 2100 kcal) over 4-week periods. BP was measured weekly for 12 weeks; 412 participants enrolled (57% women; 57% black; mean age, 48 years; mean systolic BP [SBP]/diastolic BP [DBP], 135/86 mm Hg). For those assigned control, there was no change in SBP/DBP between weeks 1 and 4 on the high-sodium diet (weekly change, -0.04/0.06 mm Hg/week) versus a progressive decline in BP on the low-sodium diet (-0.94/-0.70 mm Hg/week; P interactions between time and sodium <0.001 for SBP and DBP). For those assigned DASH, SBP/DBP changed -0.60/-0.16 mm Hg/week on the high- versus -0.42/-0.54 mm Hg/week on the low-sodium diet (P interactions between time and sodium=0.56 for SBP and 0.10 for DBP). When comparing DASH to control, DASH changed SBP/DBP by -4.36/-1.07 mm Hg after 1 week, which accounted for most of the effect observed, with no significant difference in weekly rates of change for either SBP (P interaction=0.97) or DBP (P interaction=0.70). In the context of a typical American diet, a low-sodium diet reduced BP without plateau, suggesting that the full effects of sodium reduction are not completely achieved by 4 weeks. In contrast, compared with control, DASH lowers BP within a week without further effect thereafter.

Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000608.

Keywords: antihypertensive agents; blood pressure; diet; hypertension; sodium.

Figure 1

Mean weekly systolic blood pressure (mm Hg) (A&B) and diastolic blood pressure (mm Hg) (C&D) while consuming high (squares), medium (circles), and low (diamonds) sodium levels. Means are presented according to assignment to the control (A&C) or DASH (B&D) diets. Beta’s represent weekly change in blood pressure. Vertical lines represent the 95% confidence intervals. The gray diamond represents the systolic or diastolic blood pressure measured after the run-in period at baseline.

Figure 2

Mean weekly systolic blood pressure (mm Hg) (A) and diastolic blood pressure (mm Hg) (B) while consuming the control diet (diamonds) or DASH diet (circles). Means are overlaid with quadratic linear fits to help visualize trends. Vertical lines represent the 95% confidence intervals for each mean. Gray shading represents the 95% confidence bands surrounding the quadratic models.