Dietary Sodium and Blood Pressure

To the Editor. —The meta-analysis by Midgley et al1shows a slightly smaller decrease in blood pressure than that in previous analyses, which probably is due to different selection criteria. The authors also try to suggest that salt restriction is harmful and, in particular, cite a study by Alderman and colleagues.2Clearly, they have not read the article in detail or the correspondence that followed.3In this study, salt intake was assessed only after all subjects had been carefully instructed on how to restrict their salt intake to stimulate the renin-angiotensin system so that a renin/sodium profile could be derived. It has been consistently pointed out that it is only possible to distinguish low, normal, and high renin subgroups if patients are on a low sodium intake. Moreover, it is inappropriate to use this 24-hour urinary sodium after 5 days of sodium restriction as a guide to the patient's subsequent