The Effect of Reducing Salt Intake

Reference 5 is the definitive study on the effect of sodium intake on hypertension. In this study, 412 participants were randomly assigned to eat either 1) a control diet typical of a characteristic US or 2) the DASH Diet. Within each diet group, participants ate foods with high, intermediate, and low levels of sodium for 30 consecutive days each, in random order. The study involved adults whose blood pressure exceeded 120/80 mm Hg, including those with stage 1 hypertension (a systolic blood pressure of 140 to 159 mm Hg or a diastolic blood pressure of 90 to 95 mm Hg). The targeted enrollment was 50% blacks and 50% women. The large number of blacks is an interesting factor - on the one hand, blacks are thought to suffer more from hypertension; on the other hand, the results may not be directly applicable to the majority Caucasian population.

For people on the "regular" US diet, there was a reduction in systolic blood pressure by 2.1 mm Hg (Margin of Error between 0.8 and 3.4) when going from high to intermediate sodium intake. When going from intermediate to low, there was a further reduction by 4.6 (3.2 to 5.9). So for people on a regular diet, a 6-7 mm Hg reduction in systolic pressure may be achievable by a major reduction in sodium intake. (The corresponding overall diastolic pressure reduction would be about 3 mm Hg).

For people on the DASH diet, the reduction was smaller - a 2-3 mm reduction in systolic blood pressure when undergoing a major reduction in sodium, and a 1-2 mm Hg reduction in the diastolic pressure.

However, when broken down separately to Blacks and Caucasians, we see a significant difference: Blacks have a 2 mm higher reduction with a low-salt diet compared to Caucasians. In addition, people without hypertension, only have a very small reduction in blood pressure - roughly 2 mm Hg when on a low-sodium DASH diet, and 4 mm (6 mm for blacks) when reducing sodium while on the standard diet. It seems that if one is not hypertensive, the impact of sodium reduction is not very significant! It is probably more important to modify your diet to be close to the DASH diet if you want to reduce your blood pressure (although for the Black community, there seems to be a more significant additional benefit to sodium reduction).

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Last Modification - September 1, 2008