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PART D: SCIENCE BASE

Table D7-1. Trials That Assess the Main and Interactive Effects of Salt and Potassium on Blood Pressure and Sodium Intake in Two Diets: Main Results From the DASH Sodium Trial (Sacks FM et al., 2001)

Citation Design Population Sodium Levels Tested Potassium Levels Tested Duration Main Effects of Sodium Main Effects of Potassium Interactive Effects Inter-pretation
Sacks et al., 2001 Crossover trial of three sodium levels, parallel trial of 2 diets 412 adults, % women, % AA, 135/86 mmHg 50 (L), 100 (I), 150 (H) mmol/day 1700 mg/d in control diet,
4700 mg/day in DASH diet		 30 days SBP: -7.9 mmHg (H to L) in control diet, -3.0 mmHg in DASH diet; DBP: -3.5 mmHg (H to L) in control diet, -1.6 mmHg in DASH diet SBP (DASH diet net of control): -5.9 mmHg at H, -2.2 mmHg at L; DBP (DASH diet net of control): -2.9 mmHg at H, -1.0 mmHg at L; Subadditive effect of sodium reduction and DASH diet (p<0.001) The DASH diet (rich in potassium) blunts but does not eliminate the effects of increased sodium on blood pressure. A low sodium intake blunts the effects of the control diet (low in potassium) on blood pressure.
Morris et al., 1999 parallel, sequential phases; baseline (I) with low K+Na, then 'Na loading' low K and high Na, then 'K loading' 38 men, 63% AA, <140/<90 mm Hg 15 mmol/day (basal diet), then 250 mmol/d (high salt) 30 mmol/day (basal diet), then 70 mmol (A), 70 mmol (B), 120 mmol (C), placebo (D) 6 weeks total
(2 week basal, 1 week Na loading, 3 weeks with K loading		 Pre-Post Na loading: SBP: +8.8 mmHg in Blacks (basal to high salt), +2.9 mmHg in Whites (basal to high salt); +DBP: 5.6 mmHg in Blacks (basal to high salt), +1.4 mmHg in Whites (basal to high salt) Pre-Post K loading: SBP: -4.9 mmHg in blacks (basal to A or B tx), -2.5 mmHg in whites (basal to A or B tx); DBP: -3.3 mmHg in Blacks (basal to A or B tx), -1.9 mmHg in whites (basal to A or B tx) Supplementing dietary potassium at 70 mmol/d attenuated moderate salt sensitivity in both blacks and whites (p<0.01) and at 120 mmol/d abolished salt sensitivity and suppressed the frequency and severity of salt sensitivity in blacks (n=5) to levels similar to those observed in whites. Effects of sodium and potassium based on pre-post BP change, not net of placebo. K appears to blunt the rise in blood pressure from sodium and do so in a dose-dependent fashion in blacks.
Skrabel et al., 1981 2 x 2 factorial 20 men, 21-25, all non-hypertensive, 125/73.1 mmHg 50, 200 mmol 80, 200 mmol 2wk SBP: -2.7, DBP:-3.0, both NS SBP: -1.7, DBP:-4.5, both NS SBP: -2.3, DBP:-3.5, both NS Small trial, all BP change NS
Chalmers et al., 1986 2 x 2 factorial 212 adults with hypertension, DBP: 90-100 mmHg ~80, ~150 based on 24 hr urines ~70, ~90 based on 24 hr urines 12 weeks SBP: -3.9, DBP:-3.1, both sign SBP: -5.1, DBP:-4.2, both sign SBP: -4.2, DBP:-2.6, both sign; no formal test but BP effects of increased K and reduced Na appear subadditive Increased potassium or reduced sodium, alone or together, reduce blood pressure to the same extent.

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