Salt Substitute Offers a Cheap Way to Cut Stroke Risk at Scale, Study Finds

A giant study has found that swapping out table salt for a substitute that’s at least a quarter potassium can cut stroke risk 14% among older adults and those at risk of cardiovascular events—offering a cheap, easy way to improve population health at scale.

The study, presented today during ESC Congress 2021, involved 20,995 residents from 600 villages in rural China. Most consumed diets high in salt; most had a history of hypertension and three-quarters had a history of stroke.

Results were simultaneously published in the New England Journal of Medicine.¹

The idea that lowering salt intake improves heath is nothing new. Multiple studies have shown that cutting back on salt lowers blood pressure. But tracking how a population-level intervention can reduce cardiovascular events is something else, wrote Julie R. Ingelfinger, MD, in an editorial in NEJM.²

“If the strategy is feasible over time, the salt-substitute approach might have a major public health consequence in China, and possibly, elsewhere,” she wrote, while cautioning that the findings may not apply to other groups.

For this study, villages were assigned to receive either table salt or the substitute, which was 75% salt and 25% potassium. In each village, about 35 people aged 60 and older or with high cardiovascular risk were given one of the products—enough for their entire household to use for cooking, seasoning, and food preservation. In rural China, families do their own cooking and there is no access to processed food.

Those in the salt-substitute group were encouraged to cut back on salt, as low-income groups are known to use more salt than needed in their food preparation. The table-salt group prepared food as usual.

The primary outcome was stroke, and secondary outcomes were major adverse cardiovascular events and death from any cause. Investigators also measured clinical hyperkalemia as a safety outcome. After a follow-up of 4.74 years, results showed the following:

• The mean age of participants was 65.4 years, 49.5% were female, 72.6% had stroke history, and 88.4% had hypertension history
• The rate of stroke was lower with the salt substitute, 29.14 vs 33.65 event per 1000 person-years; the rate ratio (RR) was 0.86 (95% CI, 0.77-0.96; P = .006)
• Rates of major cardiovascular events were also lower in the salt substitute group: 49.09 vs 56.29 events per 1000 person-years, for an RR of 0.87 (95% CI, 0.80-0.94; P < .001)
• The salt-substitute group had lower rates of cardiovascular death: 39.28 vs 44.61 events per 1000 person-year, for an RR of 0.88 (95% CI, 0.82-0.95; P < .001)
• Hyperkalemia was not significantly higher in the salt-substitute group: 3.35 vs 3.30 events per 1000 person-years, for an RR of 1.04 (95% CI, 0.80-1.37; P = 0.76)

The study’s principal investigator said the ability of those who used the salt substitute to cut their stroke risk—along with other cardiovascular events—with a simple intervention has implications for other developing countries with diets high in salt that have high rates of chronic disease.

“The trial result is particularly exciting because salt substitution is one of the few practical ways of achieving changes in the salt people eat,” said Bruce Neal, MB ChB, PhD, FRCP, FAHA, of the George Institute for Global Health in Sydney, Australia, in a statement. “Other salt reduction interventions have struggled to achieve large and sustained impact.’’

Neal and his co-authors cited some important limitations of their study, such as the use of only 1 salt substitute preparation, which prevented the opportunity to grade decreases in salt consumption. They also noted the lack of measured serum potassium levels. However, the study’s method of implementation, which resembled how a public or nongovernmental organization salt-substitution program might be conducted at scale, offered proof of what health gains are possible.

The study proves that a simple intervention can be “taken up very quickly at very low cost,” he said.

Salt costs $1.08 (US dollars) per kilogram in China; salt substitute is easily manufactured and costs $1.62 per kilogram. Countries that adopt a policy of implementing salt substitute can quickly shift the health of their population, Neal said.

During a press presentation ahead of his formal presentation during ESC Congress 2021, Neal showed a world map of countries with high salt consumption; developing countries were disproportionately represented. China offers a good example of what the stakes are, he said.

“A recent modeling study done for China projected that 365,000 strokes and 461,000 premature deaths could be avoided each year in China if salt substitute was proved to be effective,” Neal said. “We have now shown that it is effective, and these are the benefits for China alone. Salt substitution could be used by billions more with even greater benefits.”

References

1. Neal B, Wu Y, Feng X, et al. Effect of salt substitution on cardiovascular event and death. N Engl J Med. Published August 29, 2021. doi:10.1056/NEJMoa2105675

2. Ingelfinger J. Can salt substitution save at-risk persons from stroke? N Engl J Med. Published August 29, 2021. doi:10.1056/NEJMe2112857