Should we now abandon the low-salt diet?

Abstract

The publication in the May 2011 issue of JAMA of the paper by Stolarz-Skrzypek et al .1 once again raises previous opinions that low-salt diet in normal people can be harmful. The conclusions of that paper,1 that low-salt diet is associated with increased mortality has been heavily criticized in the US press, and the Lancet ,2 and has been impressively rebutted by the leader of the research team.3 Interestingly, in the same study,1 there was no increased mortality in those with high salt intake. The JAMA study1 was large; 3681 subjects, normal European Caucasians, daily urinary sodium excretion rates were measured as an indication of sodium intake, as recommended by He and MacGregor4 (excess sodium is excreted in the urine5). We can expect protracted debate on the rights and wrongs, for and against the ‘salt causes hypertension’ hypothesis. The issue that should be considered now is: Is there evidence to suggest that salt deprivation causes harm? The recommendation to the general public to restrict its sodium intake [mainly as ‘salt’—sodium chloride (the terms salt and sodium are often used synonymously. However, on a weight basis, salt comprises 40% sodium and 60% chloride. 1 g salt = 0.4 g sodium; 100 MEq = 2.9 g sodium = 5.8 g salt/sodium chloride = 100 mmol)] is based on a large body of opinion. Official bodies such as NICE6 and the Institute of Medicine7 repeat this recommendation in press releases, which do not include the evidence on which the advice is based and do not mention the contrary evidence. In an extreme form this is expressed as ‘a reduction in population salt intake worldwide will result in a major improvement in public health’,4 based on the fact that arterial blood pressure (BP) can be reduced in normals and hypertensives by salt restriction. The coronary …