Volume 2, Number 2, June 2001

Salt – The DASH-Sodium trial
Feng J He, Graham A MacGregor

Although meta-analyses of trials on the effect of salt reduction on blood pressure (BP) have consistently shown a significant BP reduction in hypertensive patients, it has been suggested that salt reduction has little or no such effect in normotensives. In contrast, a recent meta-analysis by our group, which included studies of modest salt reduction over a prolonged period, did show a significant decrease in BP, in both hypertensives and normotensives. In addition, a prospective study of 1173 Finnish men and 1263 Finnish women, in whom 24-hour urinary sodium excretion was measured at baseline, showed that lower salt intake was associated with lower cardiovascular mortality, and that this effect was independent of other cardiovascular risk factors.
More recently, the results of a large, controlled feeding study, the DASH sodium study, have been published. This study, in 169 hypertensive and 243 normotensive individuals, showed that lowering sodium intake reduced BP in both populations, while a combination of low sodium and the 'DASH diet' (rich in fruits, vegetables and low-fat dairy products) had the greatest effect, reducing BP by 11.5/5.7 and 7.1/3.7 mmHg in hypertensives and normotensives, respectively.
It has been shown that the fall in BP induced by salt restriction is dependent on the activation and responsiveness of the renin-angiotensin system (RAS). Salt restriction is, thus, particularly effective in subjects with less RAS responsiveness, such as blacks and the elderly.
The findings of the DASH sodium trial make a strong case for aiming to reduce salt intake in the general population and support the current government health recommendations of reduction from 10 g to 5 g salt per day. Since, in developed countries, most dietary salt comes from processed foods, a population-based effort to reduce salt intake will clearly need the cooperation of the food industry, which have historically, and for commercial reasons been reluctant to make the necessary changes.

JRAAS 2001;2:93-95.

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