Salt substitution reduces mortality, cardiovascular events, studies suggest

Key takeaways:

• Salt substitutes reduced all-cause and cardiovascular mortality, as well as cardiovascular events, in eight trials.
• However, the results might be more generalizable to older populations that follow Asian diets.

Salt substitution may reduce the risk for all-cause and cardiovascular mortality, and it may also reduce the risk for major cardiovascular events, according to a systematic review and meta-analysis of randomized controlled trials.

However, the associations were based on low- or even very low-certainty evidence, and the effect may be stronger in certain populations, researchers said.

“We had heard of salt substitutes as a promising method of reducing cardiovascular events and deaths but noticed that previous studies focused on shorter term follow-up, and we were aware that new [randomized controlled trials (RCT)] had been conducted since the last systematic review,” Hannah Greenwood, BPsychSc, a research assistant at Bond University in Australia, told Healio. “We conducted this study as we wanted to examine long-term studies only — that is, follow-up of at least 6 months — and ensure that the evidence was updated with the latest available data.”

In the systematic review and meta-analysis, published in the Annals of Internal Medicine, Greenwood and colleagues assessed 16 RCTs published through Aug. 23, 2023, in which participants (n = 35,251) used regular table salt or salt substitutions for at least 6 months.

The study’s primary outcomes were all-cause and cardiovascular mortality, major cardiovascular events (MACE) — like myocardial infarction or revascularization — and serious adverse events.

Among the RCTs, eight studied the primary outcomes. Of these, seven were conducted in China or Taiwan, three were conducted in residential facilities and seven included populations with an average age of 62 years.

According to the results, salt substitutes may reduce the risk for all-cause mortality (rate ratio [RR] = 0.88; 95% CI, 0.82-0.93) and cardiovascular mortality (RR = 0.83; 95% CI, 0.73-0.95), although both associations were based on low-certainty evidence. The researchers found that salt substitution resulted in an absolute reduction in all-cause mortality of five in 1,000 (95% CI, –3 to –7) and an absolute reduction in CVD mortality of three in 1,000 (95% CI, –1 to –5).

They also found very low-certainty evidence that salt substitution may result in a slight reduction in MACE (RR = 0.85, 95% CI, 0.71-1), and that its use did not increase serious adverse events (RR = 1.04; 95% CI, 0.87-1.25). The absolute reduction in MACE was eight in 1,000 (95% CI, 0 to –15), with one in 1,000 more serious adverse events (95% CI, 4 to –2).

Because most of the evidence was from older populations with an increased risk for CVD that followed an Asian diet, “generalizability to a population with a Western diet and/or with average cardiovascular risk is very limited,” Greenwood and colleagues noted.

According to Greenwood, primary care physicians “should consider suggesting salt substitutes to their patients looking to reduce their cardiovascular risk, especially if they are older or have existing cardiovascular risk factors, like hypertension.”

However, individual circumstances should be considered, as salt substitutes may not be suitable for all patients, "especially those with kidney disease,” she said.

Greenwood added that sodium intake is just one driver of CVD, “so salt substitutes should not be seen as a holy grail that will eliminate CVD.”

“Rather, salt substitutes are another tool to help manage cardiovascular risk, alongside medications and other nondrug approaches, including diet change, smoking cessation and exercise,” she said.

In a related editorial, J. Jaime Miranda, MD, MSc, PhD, FFPH, a professor and head of the Sydney School of Public Health at the University of Sydney, Australia, and colleagues explained that elevated BP is a major global health burden.

Thus, “we must turn our attention to effective evidence-based alternatives, such as the use of potassium-enriched salts,” they wrote. “Potassium-enriched salts are safe, can be incorporated into daily habits, and reduce sodium levels in processed foods.”

They concluded that implementing potassium-enriched salts into diets “holds promise to improve BP control and foster healthier societies on a global scale.”

References:

• Greenwood H, et al. Ann Intern Med. 2024;doi:10.7326/M23-2626
• Miranda J, et al. Ann Intern Med. 2024;doi:10.7326/M24-0860.