Is salt substitution really good for the heart?

A recent study has shown the benefits of salt substitution in reducing all-cause or cardiovascular (CV) mortality. However, the evidence remains unclear as regards lowering CV events and not increasing serious adverse events, specifically in a Western population.

A team of investigators searched the databases of PubMed, Embase, Cochrane CENTRAL, and Cinahl from inception to 23 August 2023 for randomized controlled trials (RCTs) comparing the provision of or advice to use salt substitution with no intervention or use of regular salt among adults for 6 months or longer in study duration.

Two independent investigators screened articles, extracted data, and assessed the risk of bias. The investigating team also performed random-effects meta-analyses and examined the certainty of effect estimates using the Grading of Recommendations Assessment, Development and Evaluation (GRADE).

Sixteen RCTs met the eligibility criteria, of which eight reported on mortality, major adverse CV events (MACE), and adverse events at 6 months or greater. Of the eight studies, seven were conducted in China or Taiwan, three were performed in residential facilities, and seven included populations of older adults (mean age 62 years) and/or with high CV risk.

Salt substitution reduced the risk for all-cause mortality (six RCTs; n=27,710; rate ratio [RR], 0.88, 95 percent confidence interval [CI], 0.82‒0.93; low certainty) and CV mortality (four RCTs; n=25,050; RR, 0.83, 95 percent CI, 0.73‒0.95; low certainty).

This intervention also resulted in a slight decrease in MACE (three RCTs; n=23,215; RR, 0.85, 95 percent CI, 0.71‒1.00; very low certainty) and an increase in serious adverse events (six RCTs; n=27,995; risk ratio, 1.04, 95 percent CI, 0.87‒1.25).

“The certainty of evidence is higher among populations at higher cardiovascular risk and/or following a Chinese diet,” the investigators said.