Background
Both sodium reduction and the DASH 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
We compared the effects of low versus high sodium, DASH versus control, and both (low sodium-DASH versus high sodium-control diets) on systolic BP (SBP) by baseline BP.
Methods
In the DASH-Sodium trial, adults with pre- or stage 1 hypertension, not using antihypertensive medications, were randomized to either DASH or a control diet. On either diet, participants were fed each of three sodium levels (50, 100, and 150 mmol/d at 2100 kcal) in random order over 4 weeks separated by 5-day breaks. Strata of baseline SBP were <130, 130-139, 140-149, and ≥150 mmHg.
Results
Of 412 participants, 57% were women, and 57% were black; mean age was 48 years, and mean SBP/DBP was 135/86 mmHg. 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 mmHg across respective baseline SBP strata (listed above) (P-trend=0.004). In the context of high sodium, consuming the DASH compared to the control diet was associated with mean SBP differences of -4.5, -4.3, -4.7, and -10.6 mmHg, respectively (P-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 mmHg, respectively (P-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 mmHg) 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 mmHg.