In patients with heart failure, a low-sodium diet does not improve outcomes

A common contributor to acute exacerbations of chronic heart failure is having one or more high-sodium meals prior to the onset of symptoms. It seems reasonable, then, to recommend that patients with heart failure adhere to a low-sodium diet to reduce readmissions and mortality and improve quality of life. But until recently, there was limited evidence to support or refute this line of thinking. In a 2014 editorial, American Family Physician associate editor Barry Weiss, MD discussed several studies showing that a low-sodium (less than 1,800 mg per day) diet produced no benefits and increased mortality compared to a normal diet in heart failure patients in the outpatient and inpatient settings. Consequently, he advised that "based on current evidence and until further studies are completed, patients with heart failure should probably be discouraged from reducing their sodium consumption to less than 2,300 mg per day."

Two subsequent systematic reviews of studies of dietary sodium restriction in heart failure also questioned low-sodium dogma. A 2018 review of 9 randomized trials with 479 participants with heart failure found insufficient data on cardiovascular-associated and all-cause mortality, stroke, and myocardial infarction and conflicting evidence on changes in New York Heart Association functional class. Similarly, a 2021 systematic review and meta-analysis of 10 trials (1011 participants) found that low-sodium diets did not improve quality of life and possibly increased readmission rates and mortality. However, most trials included fewer to 100 participants, leaving open the possibility that a larger trial powered to detect differences in clinical outcomes could still show benefits.

Last month, the Study of Dietary Intervention under 100 mmol in Heart Failure (SODIUM-HF) trial, with 806 participants from 26 sites in Australia, Canada, Chile, Colombia, Mexico, and New Zealand reported its primary findings. All participants in this pragmatic randomized trial were receiving optimally tolerated guideline-directed medical treatment for chronic heart failure. Participants were randomly assigned to usual care or a low sodium diet of <100 mmol/day (<1,500 mg/day). The primary outcome was a composite of cardiovascular-related hospitalization, emergency department visit, and all-cause mortality within 12 months. Median sodium intake decreased in the low-sodium group from 2,286 mg to 1,658 mg/day and in the usual care group from 2,119 mg to 2,073 mg/day by the end of the trial. However, in an intention-to-treat analysis, researchers found no statistical differences between the groups in the composite outcome or in each of the individual outcomes.

As Dr. Weiss cautioned in his AFP editorial, "the possibility that aggressive sodium restriction may lead to unfavorable outcomes in patients with heart failure should not ... be misconstrued as meaning that we should lose our focus on reducing sodium intake in the general population." Indeed, there is good evidence that population-level interventions are effective in preventing cardiovascular disease, including a large Chinese randomized trial of a salt substitute that Dr. Jennifer Middleton discussed in a previous AFP Community Blog post. That's why recent guidance for industry from the U.S. Food and Drug Administration that aims to reduce the average American's daily sodium intake from 3,400 mg to 3,000 mg/day over the next few years could also have a positive public health impact.