DASH Diet, Sodium, and Baseline Blood Pressure
What is the comparative effect 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?
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 (a diet rich in fruits, vegetables, and low-fat dairy products, and reduced in saturated fat, cholesterol, and sugar-containing beverages) or a control diet (typical of American diet). All meals were provided including lunch and dinner at study site and breakfast and snacks off site. On either diet, participants were fed each of three 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, 130-139, 140-149, and ≥150 mm Hg.
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).
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.
To place in clinical perspective: 1 tsp salt = 6 g salt = 2400 mg sodium = 104 mmol. Salt-sensitive hypertension has been well characterized and attributable to genetic and environmental factors, renal function, and components of the metabolic syndrome. There is evidence that salt sensitivity influences the development of organ damage, even independently in part of BP levels and the occurrence of hypertension. In addition, several observational studies indicate that salt sensitivity is associated with a higher rate of cardiovascular events and mortality. The low salt DASH diet handouts for patient education are readily available and easily followed.
Keywords: Antihypertensive Agents, AHA17, AHA Annual Scientific Sessions, Beverages, Blood Pressure, Breakfast, Cholesterol, Dairy Products, Diet, Sodium-Restricted, Fruit, Hypertension, Lunch, Meals, Metabolic Syndrome X, Primary Prevention, Snacks, Sodium, Vascular Diseases, Vegetables
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