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Lowering Salt Intake: Collective SBP Benefit Trumps Individual Variation

We still can't predict which individuals will derive benefit from reduced dietary salt intake.

Reducing salt intake lowers the average blood pressure in patient populations, but what about individual responses? These researchers studied the range and consistency of systolic BP responses to changes in salt intake among participants in the Dietary Approaches to Stop Hypertension (DASH)-Sodium Trial. The analysis was restricted to 188 participants who ate control diets at the 3 sodium levels tested (high, intermediate, and low); diets were eaten in random order for 30 days each, with 2-week high-sodium run-ins between them. Mean urinary sodium excretion (in mmol/day) was 140, 104, and 62 for the 3 diet-sodium levels, respectively.

On average, SBP was a highly significant 6.7 mm Hg lower with the low-sodium diet than with the high-sodium diet. However, individual SBP benefits with the low-sodium diet varied widely -- from 32 mm Hg lower to 17 mm Hg higher -- compared with the high-sodium diet. Just over one third of participants saw a reduction of at least 10 mm Hg with the low-sodium diet.

When the researchers assessed the consistency of individual SBP responses (in part by comparing data from the high-sodium run-in periods with data from the high-sodium treatment period), they found a great deal of inconsistency within individuals, whether they were hypertensive at baseline or not. In other words, it was difficult to identify specific individuals as sodium responders.

Comment: These data support the current recommendation of encouraging people in general (rather than only some individuals) to lower salt intake as one of several strategies for preventing and controlling high blood pressure. The overall benefit stands despite our present inability to predict which individuals will derive benefit and why.

— Joel M. Gore, MD

Published in Journal Watch Cardiology November 28, 2003

Citation(s):

Obarzanek E et al. Individual blood pressure responses to changes in salt intake: Results from the DASH-Sodium Trial. Hypertension 2003 Oct; 42:459-67.

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