Researchers from Australia, China, UK, and USA conducted a modelling study based on a nationwide intervention Salt Substitute and Stroke Study to estimate the effect of salt substitution on stroke risk.
Previous studies had observed that potassium-enriched salt substitutes were associated with a lower risk of death from CVD, due to its blood pressure lowering effects.
However, the potential effect of potassium-enriched salt substitutes to replace dietary salt in China had not been quantified.
Researchers claimed: “Our results suggest that a person in the general population would be more likely to survive with the intervention than without. Although our estimates can provide guidance to policy makers, large clinical studies (such as the ongoing Salt Substitute and Stroke Study) are needed to evaluate the potential benefits versus harms of salt substitution.”
They published the findings in the British Medical Journal.
The model study was based on the ongoing Salt Substitute and Stroke Study, a randomised controlled trial conducted in five provinces, across 600 villages, in rural Northern China. Researchers used this study to model the effect on China’s entire population.
They explained: “The Salt Substitute and Stroke Study is a large-scale pragmatic trial, its effects are likely to reasonably approximate what a national scale intervention can achieve.”
The salt substitute used in the study contained 70% sodium chloride and 30% potassium chloride. It was distributed free of charge to individuals (20g/day) to replace table salt.
Researchers reported that the use of salt substitutes was associated with lowered systolic blood pressure and the effects increased with age.
At a baseline age of 65, systolic blood pressure was reduced by 2.82 mm Hg (p=0.004), and for each additional year of age, blood pressure was further reduced by 0.13 mm Hg (p=0.09).
Researchers estimated that this systolic blood pressure lowering effect of salt substitution could prevent about 450,000 CVD deaths. “We estimated that the intervention could prevent about one in nine deaths from cardiovascular disease in China.”
China’s sodium intake (mean 4.1g/day) is more than double the limit recommended by the World Health Organization, and 45% of the population have high blood pressure, which is a leading cause of death.
Limitations and future directions
While their findings suggest that the intervention would have a large effect on the burden of CVD in China, they said the effect of salt substitution could decline in the future, as more people were consuming processed and pre-prepared foods, which is another major source of sodium in the diet.
Researchers acknowledged another limitation in their study: “We did not consider the additional benefits of partial salt substitution on non-cardiovascular outcomes, such as stomach cancer, which is prevalent in parts of China, or pre-eclampsia in pregnant women, which might lead to underestimation of the net benefits of the intervention.”
“Future studies should evaluate the benefits of potassium enriched salt substitutes in specific subpopulations, such as pregnant women, and for the prevention of non-cardiovascular disease outcomes.”
They concluded: “Our modelling study does not prove that a national intervention to encourage potassium enriched salt substitutes will prevent cardiovascular disease; rather, it provides important quantitative estimates, corresponding uncertainty, and assessments of the sensitivity of the findings to different inputs to guide the design, implementation, and evaluation of an appropriate intervention in a national population.”
“Estimated population wide benefits and risks in China of lowering sodium through potassium enriched salt substitution: modelling study”
Authors: Matti Marklund, et al.