Salt substitute prevents cardiovascular events in ‘landmark’ study

The Salt Substitute and Stroke Study (SSaSS) showed the simple act of swapping table salt with a potassium-enriched salt-substitute had significant impacts on cardiovascular health and mortality. The finding is “relevant to everybody who eats,” said Dr. Bruce Neal, professor of medicine at the University of New South Wales in Sydney, Australia. He presented results from the SSaSS at the recent annual (virtual) meeting of the Canadian Cardiovascular Society. The open randomized trial was launched in 2014 and enrolled 20,995 adults aged 60 years and over with a history of either stroke or poorly controlled blood pressure. The cohort came from 600 rural villages across China with about 35 participants in each village. Participants had no self-reported history of severe kidney disease, or use of either potassium supplements or potassium-sparing diuretics. The goal was to define the effects of salt substitute, compared to regular salt, on stroke. Secondary outcomes included major adverse cardiovascular events and total mortality. Randomization was done by village, with residents in 300 villages (10,504 participants) randomized to use a salt substitute, and the other 300 to regular table salt (100% sodium chloride). The salt substitute consisted of 75% sodium chloride and 25% potassium chloride. Participants used salt or the substitute as they normally would. Health data were collected at baseline, and years one, two and five. Read: Hearts from opioid overdose donors safe for transplants “We scheduled six-monthly follow-up for all participants. We routinely collected health data from health insurance system and mortality databases every six months . . . we also did face-to-face follow-up for the first two years, and at the final visit,” he said. In-person measurements of blood pressure and urinary electrolytes were conducted annually in a subset of 54 to 140 villages. Factors such as age (an average of 65 years), history of stroke, uncontrolled blood pressure, diabetes, blood pressure and other measures were similar between the groups at baseline. At baseline, 73% had a history of stroke, 60% had uncontrolled blood pressure, and 30% had both. Twenty-thee per cent used ACE inhibitors or ARBs; calcium antagonists (42%); or antihypertensives (80%). A total of 90% of participants reported hypertension, and mean blood pressure was 154/89 mmHg. Mean 24-hour urinate sodium was 182-191 mmol of sodium and 36 mmol urinary potassium. Participants chronic kidney disease or risk for hyperkalemia were excluded. At five years, 92% of people in the intervention group were still using the salt substitute, and 6% of the control group had started using salt substitute. The mean difference in systolic blood pressure between groups was 3.34 mmHg, with the salt-substitute villagers having lower pressure. The mean difference in diastolic blood pressure was .67 mmHg between the groups. Results also showed a drop in 24-hour sodium excretion in the salt substitute group. The difference between the two both groups changed from a mean of 9.96 mmol at baseline to -15.21 mmol at five years. Each of the study years also showed fewer strokes occurring in the salt-substitute cohort. A total of 3,123 strokes were recorded. Expressed in events per 1,000 person years, there were 29.14 strokes in the salt substitute group and 33.65 in the regular salt users. “There was very clear evidence of protection against stroke,” Dr. Neal said. There was a total of 5,241 major adverse cardiovascular events in 4,499 people with significantly more happening in salt users with a rate ratio of 0.87. As for hyperkalemia, there was a total of 331 events with a rate ratio of 1.04. “It’s a cluster randomized trial and you analyze by rates in clusters, not numbers of events . . . if I give you numbers people will try and estimate the effect based on those numbers and get the wrong answer,” he told The Medical Post in an email. Mortality differed between salt and substitute users with death-from-any-cause occurring in 39.28 events per 1,000 person-years compared to 44.61 in the regular salt users. Generally, men using salt substitutes had slightly more benefit than women for most measures, he said. “We believe this result is probably relevant to everyone that eats salt, because the nature of the associations between sodium, potassium, and blood pressure, and blood pressure and clinical outcomes are highly consistent across diverse populations,” Dr. Neal said. A substitute containing potassium was used because potassium has known blood pressure lowering effects beyond reducing dietary sodium. “Salt manufacturers and retailers, worldwide, could switch to producing and marketing salt substitute at scale; the food processing industry could reformulate products to lower-sodium, higher-potassium compositions; governments could design policies to promote salt substitute and discourage regular salt use; and consumers could cook, season, and preserve foods with salt substitute, not regular salt,” he said. The results presented did not address whether participants consumed packaged foods or cooking sauces such as soy sauce. Dr. Padma Kaul, professor of medicine at the University of Alberta, questioned whether salt reduction alone could be an effective intervention, “and whether other compositions of salt substitutes had been considered.” She spoke at the CCS and was not involved in the study. Cautions for some when it comes to salt substitutes According to the Harvard Heart Letter, Brigham and Women’s Hospital cardiologist Dr. Deepak Bhatt stated cautions around potassium supplementation. Both too little or too much is problematic, and factors such as medications can drive levels in either direction. Some diuretics lower potassium levels, others raise it. Certain ACE inhibitors, such as lisinopril or ramipril, can raise potassium, while common painkillers such as ibuprofen or naproxen lower it. The kidneys help regulate potassium levels, but age, diabetes, heart failure, and other conditions can impair kidney function. “As a result, potassium levels can rise to high levels, leading to dangerous heart rhythm problems and even cardiac arrest,” he wrote. Many grocery stores offer salt substitutes containing potassium. “People trying to curb their sodium intake may try these products. A mere one-quarter teaspoon of one brand contains about 800 mg of potassium. If you take a potassium-sparing diuretic, such as spironolactone, you should avoid salt substitutes and limit high-potassium foods,” he wrote. For kidney patients, there are commercially available salt substitutes which do not contain potassium.

Salt substitute prevents cardiovascular events in ‘landmark’ study

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