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Salt substitution found to reduce death, stroke, heart events by 12% to 14%

Journal
The New England Journal of Medicine
Reuters Health - 30/08/2021 - If you've had a stroke, or you're over 60 with high blood pressure, switching to a salt substitute can cut your risk of stroke, major cardiovascular events, and death by as much as 14%, doctors behind a massive trial of nearly 21,000 Chinese report.

The cluster-randomized test, covering nearly five years, involved people from 600 villages in rural China. Half the villages received regular salt while the rest were given a salt substitute consisting of 70% sodium chloride and 30% potassium chloride.

Stroke rates in the salt substitute group were 14% lower - at 29 cases per 1,000 persons per year versus 34 with salt (P=0.006).

The rate of major cardiovascular events was 13% lower, with 49 events compared with 56 with salt.

There were 39 deaths per 1,000 persons per year among salt substitute users and 45 in the regular salt group, a 12% reduction over the period of the study.

Among deaths from vascular causes alone, substitute users had a rate that was 13% lower, with 23 events per 1,000 persons per year versus 26 in volunteers who did not make the switch (P<0.001).

The results of the Salt Substitute and Stroke Study (SSaSS) "appear impressive. If the strategy is feasible over time, the salt-substitute approach might have a major public health consequence in China, and possibly, elsewhere," writes Dr. Julie Ingelfinger, an editor at the New England Journal of Medicine, where the study appears.

But many questions remain, such as whether a different type of salt substitute would work equally well and whether a similar effect would be seen outside China, she adds in her editorial. The study offers "some intriguing hints, but wider effectiveness (of the strategy) is hard to predict, given limited generalizability," Dr. Ingelfinger notes.

But the lead author of the study, Dr. Bruce Neal of The George Institute for Global Health at Peking University Health Science Center, in Beijing, told Reuters Health that "we know that if you look at any population around the world, the physiology of sodium, potassium, and blood pressure is strikingly constant. So the likelihood that the underlying mechanism by which salt substitution achieved its benefit, which is lowering blood pressure, is likely to hold across populations."

"If we made the switch, the implications would be huge," he said in a telephone interview. "We're talking literally millions of heart attacks, strokes, and premature deaths that could be averted every year. It's low cost, potentially scalable, and it's something you don't want people and governments to miss out on."

The findings were also reported at the European Society of Cardiology Congress 2021.

The study was undertaken to supplement the absence of large controlled trials on the clinical impact of using a salt substitute, to assess the risk of hyperkalemia, and to address concerns about sudden death if salt substitutes are used in patients with serious kidney disease, a fear that has tempered their use in the general population.

The volunteers had either a history of stroke or poorly controlled high blood pressure, with a systolic reading of 160 mmHg or higher without medication or 140 mmHg or higher with hypertensive therapy.

Potential participants were excluded if they said they had kidney disease.

At baseline, 73% had a history of stroke and 88% had been diagnosed with hypertension; 79% were taking at least one drug for high blood pressure.

The reduced-sodium salt substitute was provided free of charge to the family unit of the volunteers.

Only two people were found to have definite or probable hyperkalemia. The cases of possible hyperkalemia were comparable between the two groups.

"Use of the salt substitute was not associated with any apparent serious adverse events," the researchers reports, adding that the data "provide reassurance about the efficacy and safety of sodium-intake reduction for the prevention of cardiovascular events and death."

The team says the degree of protection offered by the salt substitute is comparable to what was seen in a 2020 study in the British Medical Journal that estimated that 365,000 strokes, 461,000 premature deaths and 1.2 million vascular events could be averted each year in China if a substitute was used across the country.

Cost could be a problem in some countries, which is why the researchers plan to lobby individual countries to subsidize the price of salt substitutes.

The researchers say consumers who don't have kidney disease should make the switch, salt manufacturers and retailers should start mass producing and marketing salt substitutes, and governments should promote salt substitutes and discourage regular salt use.

The switch isn't effortless, said Dr. Neal, a professor of medicine. There can be a slight difference in taste unless flavor enhancers are added and its chemistry may occasionally require some small adjustments in cooking and baking.

But in developed countries where people eat a lot of processed food, "I'm sure there are tens of thousands of products where food manufacturers could very rapidly make the change if they wanted to," he said.

The study was funded by the National Health and Medical Research Council of Australia.

SOURCES: https://bit.ly/3Dt5sDt and https://bit.ly/3BjoCd6 The New England Journal of Medicine, online August 29, 2021.

By Gene Emery



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