Switching to salt substitute decreased stroke risk by 14%
Click Here to Manage Email Alerts
Switching from regular salt to a salt substitute reduced the risk for stroke, major CV events and death in a large trial of adults in rural China with a history of stroke or high risk for stroke.
Among nearly 21,000 adults and over a mean follow-up of 4.74 years, the rate of stroke was 14% lower with use of a salt substitute compared with regular salt (29.14 vs. 33.65 events per 1,000 person-years; RR = 0.85; 95% CI, 0.77-0.96; P = .006).
Results of the Salt Substitute and Stroke Study (SaSS) were presented at the European Society of Cardiology Congress and simultaneously published in The New England Journal of Medicine.
“The rationale for salt substitutes is that higher dietary sodium consumption and lower dietary potassium consumption is associated with elevated BP levels, and potassium-enriched salt substitutes have a dual BP-lowering effect,” Bruce Neal, MB, ChB, PhD, scientific director at The George Institute for Global Health, said during a press conference. “Before we did SSaSS, we had pretty good evidence that salt substitutes did lower BP, but we lacked data about their effect on strokes and heart attacks. There were also concerns about supplementing people’s diets with potassium, because it could cause hyperkalemia in people with severe kidney disease.”
Evidence of CV protection
The open-label, cluster-randomized trial enrolled 20,995 adults from rural villages in China who had a history of stroke or were aged 60 years and older and had high BP. The participants’ mean age was 65 years, 49.5% were women, 72.6% had a history of stroke and 88.4% had hypertension.
Participants were randomly assigned to use regular salt or a salt substitute consisting of 70% sodium chloride and 25% potassium chloride. Participants were instructed to use the regular salt as they usually would or to use the salt substitute in place of regular salt for cooking, seasoning and food preservation, more sparingly than their previous use of regular salt.
In addition to the reduction in the primary outcome of stroke, the rate of major adverse CV events, a composite of nonfatal stroke, nonfatal acute coronary syndrome or death from vascular causes, was 13% lower among participants in the salt substitute group (49.09 events vs. 56.29 events per 1,000 person-years; RR = 0.87; 95% CI, 0.8-0.94; P < .001). All-cause mortality was 12% lower in the salt substitute group (39.28 events vs. 44.61 events per 1,000 person-years; RR = 0.88; 95% CI, 0.82-0.95; P < .001).
The researchers calculated a mean different in systolic BP of –3.34 mm Hg).
There were no between-group differences in rate of serious adverse events attributed to hyperkalemia.
‘Intriguing hints’ of benefit
The study is one of the largest dietary intervention trials completed, Neal said.
“The key question is whether the results from SSaSS, done in China, are likely to be generalizable to other populations,” Neal said. “The answer to that is almost certainly yes. The way the body manages sodium, potassium, the associations with BP, are highly constant among diverse populations around the world.”
In a related editorial, Julie R. Ingelfinger, MD, professor of pediatrics at Harvard Medical School, senior consultant in pediatric nephrology and pediatrician at Massachusetts General Hospital for Children and Massachusetts General Hospital, and a deputy editor of NEJM, noted that processed food is rarely used in the rural Chinese villages studied in SSaSS; dietary sodium chloride is added during food preparation within each household — a sharp contrast with typical Western diets.
“Commercial food preservation adds much sodium chloride to the diet and the use of salt substitutes would not even begin to account for most salt intake,” Ingelfinger wrote.
Calling the results impressive, Ingelfinger wrote that the salt-substitute approach might have a major public health consequence in China, and possibly elsewhere, if the strategy is feasible over time.
“Overall, SSaSS provides some intriguing hints, but wider effectiveness is hard to predict, given limited generalizability,” Ingelfinger wrote.
References:
- Neal B, et al. N Engl J Med. 2021;doi:10.1056/NEJMoa2105675.
- Ingelfinger J. N Engl J Med. 2021;doi:10.1056/NEJMe2112857.
Perspective
Back to Top
Eva Prescott, MD, DMSc, FESC
This is a great trial. The authors are to be congratulated on performing a cluster-randomized trial in 600 villages and including more than 20,000 individuals with previous stroke or aged at least 60 years with poorly controlled hypertension. The participants were followed for a mean of 5 years for important hard outcomes and the study seems to be of high quality and meticulously conducted. Results show that the study participants were compliant —a reduction in sodium secretion and increase in potassium secretion — and had a reduction in BP and a significant and clinically relevant reduction in the primary and secondary outcomes. Notably, there did not seem to be risk of hyperkalemia, which was a worry when substituting sodium for potassium.
The study confirms that BP reduction can be achieved by replacing sodium for potassium and — the novelty here — that this also translates into benefits in outcome, both stroke and all-cause mortality. There was also an unexpected effect on nonvascular mortality, but this may be related to the imprecise registration of cause of death in some cases, as noted by the authors.
The implications of the trial are that salt substitution should probably be implemented much more than currently done, particularly in areas where medical treatment is not optimal. However, the intervention was only aimed at individuals with poorly controlled BP or stroke and individuals with impaired kidney function were excluded. Whether this approach can be generalized to the entire population is therefore unknown. Thus, simple implementation in entire populations may be tricky.
Perspective
Back to Top
Kim Allan Williams, MD, MACC, FAHA, MASNC, FESC
This is a highly impactful study because of its size and careful analysis. It clearly shows that a reduction of ingested sodium, and a substitutionary increase in ingested potassium, results in a reduction of stroke, CV events and mortality, ranging from 12% to 14% in each case. There was a small price to pay in terms of hyperkalemia. Importantly, this opens the question to how much salt in execution is optimal. Many of the salt substitutes sold in the United States have no sodium, contain purely potassium chloride, and have not been scrutinized to this degree.
Collapse
Neal B, et al. Hot Line: SSaSS. Presented at: European Society of Cardiology Congress; Aug. 27-30, 2021 (virtual meeting).
Read more about
Click Here to Manage Email Alerts