The WHO recommends daily sodium intake of less than 2 g, based on relatively short trials in which the effect of sodium intake on blood pressure was assessed. In this study, researchers analyzed data for 28,880 patients in two international clinical trials of an angiotensin-receptor blocker; most patients (mean age, 67; 70% men) had histories of myocardial infarction, stroke, hypertension, or diabetes. People with congestive heart failure (CHF), decreased renal function, or uncontrolled hypertension were excluded. Mean daily sodium excretion (a surrogate for sodium intake) was 4.77 g, and daily potassium excretion was 2.19 g.

At 5 years, a composite outcome of cardiovascular mortality, myocardial infarction, stroke, and hospitalization for CHF occurred in 4729 patients. Patients with urinary sodium excretion of 4 to 6 g daily had the lowest risk for the composite outcome. Risk was higher by 21%, 16%, 15%, and 49% for patients with daily excretion of <2 g, 2–3 g, 7–8 g, and >8 g, respectively. Compared with patients who had daily potassium excretion of <1.5 g, risk for stroke was 32% lower in those with excretion of >3 g. These analyses were adjusted for numerous clinical and demographic factors.

Comment: This J-shaped relation between sodium intake and cardiovascular outcomes conflicts with current recommendations to limit daily sodium intake to 2 g. However, an editorialist is unconvinced and believes that randomized trials are needed to account for confounding caused by preexisting disease and risk factors. The small number of patients with low sodium intake — 3% of the total sample had urinary excretion <2 g daily — also tempers the results. Consuming a diet high in natural foods and low in processed foods would result in a lower sodium–potassium ratio –– which could be more important than the actual intake levels.

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine December 13, 2011