Cluster-randomized trial
The SSaSS was an open-label, cluster-randomized trial involving 20,995 people from 600 villages in rural China who had a history of stroke or were 60 years of age or older and had uncontrolled hypertension. Patients with a history of severe kidney disease and those taking potassium supplements or potassium-sparing diuretics were excluded.
They were randomly assigned in a 1:1 ratio to the intervention group, in which the participants used a salt substitute (roughly 75% sodium chloride and 25% potassium chloride), or to the control group, in which the participants continued to use regular salt (100% sodium chloride).
Results showed that after a mean follow-up of 4.74 years, systolic blood pressure was reduced by 3.3 mm Hg in the salt substitute group.
The rate of stroke, the primary endpoint, was 29.14 events per 1,000 person-years in the salt substitute group vs. 33.65 events per 1,000 person-years with regular salt (rate ratio, 0.86; 95% confidence interval, 0.77-0.96; P = .006).
The rates of major cardiovascular events were 49.09 events per 1,000 person-years in the salt substitute group vs. 56.29 events per 1,000 person-years in those using regular salt (rate ratio, 0.87; 95% CI, 0.80-0.94; P < .001).
And the rate of death was 39.28 events per 1,000 person-years with the salt substitute vs. 44.61 events per 1,000 person-years with regular salt (rate ratio, 0.88; 95% CI, 0.82-0.95; P < .001).
The rate of serious adverse events attributed to hyperkalemia was not significantly higher with the salt substitute than with regular salt (3.35 events vs. 3.30 events per 1,000 person-years; rate ratio, 1.04; 95% CI, 0.80-1.37; P = .76).
Dr. Neal reported that 7%-8% of the control group started using salt substitute over the study period, so these results have likely underestimated the true effect of switching to a salt substitute product.
Noting that about 10 million cardiovascular events occur each year in China, he said the study results suggested that using salt substitute instead of regular salt could prevent about 10% of these events.
Food manufacturers must make changes
Dr. Neal acknowledged that a limitation of the study was the fact it was conducted in a single country, which would raise issues of generalizability. But he said he believes the results are generalizable to other populations.
Those who would get the most benefit from switching to a salt substitute are those who consume large amounts of discretionary salt – salt added at home at the time of cooking for preservation of food or seasoning. “This is salt that is easy to replace with salt substitute,” Dr. Neal noted.
“There are more than 5 billion people in the world that consume more than 50% of their salt intake as discretionary salt – mainly in the developing world. These people would expect to get significant health benefits from a switch to salt substitute.”
He pointed out that salt substitute is low cost and is easy to manufacture. “Salt substitutes cost around 50% more than regular salt, but this translates into just a dollar or two per person per year to make the switch.”
Dr. Neal said the results also apply to higher-income countries but must be implemented by governments and food manufactures, as most salt in these countries comes from processed foods.
“This study provides strong evidence to take to the food industry,” he concluded. “We would like to see food manufacturers switch to using salt substitute and for salt substitute products to be widely available on supermarket shelves. We also urge governments to take action to promote use of salt substitutes over regular salt. This could take the form of taxing regular salt or subsidies for use of salt substitutes.”
The SSaSS was supported by grants from the National Health and Medical Research Council of Australia. Dr. Neal reports no disclosures. Dr. Ingelfinger is employed by the New England Journal of Medicine as deputy editor.
A version of this article first appeared on Medscape.com.