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

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.