We’ve known for a long time that some people are salt sensitive – ie, when salt is ingested in amounts greater than required to maintain homeostasis blood pressure rises as does the likelihood of stroke and other cardiovascular diseases. The remainder of humanity can safely ingest large amounts of salt without hypertension and its associated CV diseases. A study in the current issue of the New England Journal of Medicine looks at the effect of salt substitute on CV disease. It’s abstract is below.
Salt substitutes with reduced sodium levels and increased potassium levels have been shown to lower blood pressure, but their effects on cardiovascular and safety outcomes are uncertain.
We conducted an open-label, cluster-randomized trial involving persons from 600 villages in rural China. The participants had a history of stroke or were 60 years of age or older and had high blood pressure. The villages were randomly assigned in a 1:1 ratio to the intervention group, in which the participants used a salt substitute (75% sodium chloride and 25% potassium chloride by mass), or to the control group, in which the participants continued to use regular salt (100% sodium chloride). The primary outcome was stroke, the secondary outcomes were major adverse cardiovascular events and death from any cause, and the safety outcome was clinical hyperkalemia.
A total of 20,995 persons were enrolled in the trial. The mean age of the participants was 65.4 years, and 49.5% were female, 72.6% had a history of stroke, and 88.4% a history of hypertension. The mean duration of follow-up was 4.74 years. The rate of stroke was lower with the salt substitute than with regular salt (29.14 events vs. 33.65 events per 1000 person-years; rate ratio, 0.86; 95% confidence interval [CI], 0.77 to 0.96; P=0.006), as were the rates of major cardiovascular events (49.09 events vs. 56.29 events per 1000 person-years; rate ratio, 0.87; 95% CI, 0.80 to 0.94; P<0.001) and death (39.28 events vs. 44.61 events per 1000 person-years; rate ratio, 0.88; 95% CI, 0.82 to 0.95; P<0.001). 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 1000 person-years; rate ratio, 1.04; 95% CI, 0.80 to 1.37; P=0.76). CONCLUSIONS Among persons who had a history of stroke or were 60 years of age or older and had high blood pressure, the rates of stroke, major cardiovascular events, and death from any cause were lower with the salt substitute than with regular salt.
Among persons who had a history of stroke or were 60 years of age or older and had high blood pressure, the rates of stroke, major cardiovascular events, and death from any cause were lower with the salt substitute than with regular salt.
There’s less to this study than seen at first glance. As pointed out by Julie Ingelfinger in an accompanying editorial, it was performed in rural China where high salt containing processed foods are not widely available. Thus, almost all the salt in the subjects diet was added during preparation unlike the salt intake in most of the industrialized portions of the world where much of the salt ingested is added by the processor rather than the consumer.
That caveat aside, the subjects who were at high risk for major CV events had a statistically lower incidence of such events when 75% salt and 25% potassium chloride was compared to those using 100% salt. But look at the graphs below. The effect of the NaCl + KCL diet was very small. One must at least wonder if this dietary alteration translates into a clinically significant effect. Adding to the small differences is, as mentioned, that this type of dietary maneuver would be almost impossible to duplicate in most of the rest of the world. On the other hand, individuals at high risk for CV disease can on their own reduce salt intake – realizing, of course, that it’s very hard to do.
Finally, a nomenclatural oddity. The study is, at least in part, from Peking University in Beijing, China. We seem to have reached the point where the only solution is to ban all nouns. But, on the other hand, you can feel relieved of cultural misappropriation the next time you attend a performance of Puccini’s Turandot which is set in Peking.