PARIS — A randomized trial in Peru shows that replacing high-sodium salt at the community level lowers blood pressure (BP), particularly in high-risk groups, and halves the incidence of new hypertension.
Replacing regular high-sodium salt with a substitute containing 75% sodium and 25% potassium reduced overall systolic BP by 1.23 mm Hg (P = .004) and diastolic BP by 0.72 mm Hg (P = .022) from a baseline average of 113/72 mm Hg.
Systolic BP fell by 1.92 mm Hg among residents with hypertension and by 2.17 mm Hg in those aged 60 years and older.
“We have to remind ourselves that even modest decreases in blood pressure at the population level bring us larger gains and this is the main message of the study,” senior author J. Jaime Miranda, MD, Centro de Excelencia en Enfermedades Cronicas, Lima, Peru, said to a receptive crowd at the European College of Cardiology (ESC) Congress 2019.
Previous work has shown that even a 2–mm Hg reduction in systolic BP can lower stroke mortality by 10% and mortality from ischemic heart disease or other vascular causes in middle age by 7%. Recent studies also have linked potassium supplementation with reduced BP.
Nevertheless, high-risk strategies targeting susceptible individuals have failed to make significant inroads, and hypertension rates and nonadherence to medication remain global concerns. “That’s why we decided to approach this from a different angle and go wide and introduce a new product, a salt substitute, at the population level,” he said.
Based on prior work by the team showing that the sodium content of salt could be reduced by up to 35% and still be palatable, the researchers combined equal parts regular salt containing 100% sodium and a commercially available product consisting of 50% sodium and 50% potassium.
The new salt substitute, named Liz, was launched in six semi-rural villages in Tumbes, an area in northern Peru with about 200,000 residents, a poverty level of about 25%, and hypertension in 27% of those aged at least 35 years.
To guarantee full replacement of salt, Liz salt was provided free of charge but in exchange for regular salt, Miranda said. The exchanges included households, bakeries, community kitchens, food vendors, and restaurants. A bag of Liz and a 1-kg refillable plastic container were delivered door-to-door and also promoted by social media and community events.
The stepped-wedge trial enrolled all adults aged 18 years and older between 2014 and 2017, with participation reaching 91.2% (2376/2605 persons). Residents with chronic kidney disease or heart disease or those taking digoxin were excluded. BP was measured every 5 months, for a total of 7 measurements.
At baseline, 42.5% of patients were overweight, 24.7% were obese, and 18.3% had hypertension. The mean age was 43.3 years, with 26.6% of patients aged 18 to 29.
After accounting for clustering at the village level, age, sex, education, wealth index, and body mass index, the incidence of hypertension was halved (hazard ratio, 0.45; 95% CI, 0.31 – 0.66; P < .001), Miranda said as applause rippled through the hotline session.
A random 24-hour urine sampling of 600 participants showed that sodium levels remained unchanged from baseline (3.94 g vs 3.95 g) but that potassium levels increased from 1.97 g to 2.60 g (P < .001).
“Our biggest fear was that as soon as we left the door, they would go and throw it away,” but the rise in potassium levels “gave us a strong indication that they did engage in the program and used it,” he said.
The study shows that switching to low-sodium, high-potassium salts not only is feasible but demonstrates population-wide benefits by shifting the BP distribution of the population and halving hypertension incidence, Miranda said. Future considerations are whether sodium in the salt substitute could go below 25% and whether better results could be expected in older populations or those with higher baseline SBP.
“To do a study with this innovation and stepped-wedge design, we can all vote for this. Congratulations,” session co-chair Keith Fox, MD, University of Edinburgh, Scotland, said to a burst of applause.
Invited discussant Bruce Neal, MD, University of Sydney, Australia, said most salt substitution trials have shown larger BP reductions but congratulated the authors on an enormous project and “an important addition to the science about this type of product.”
To maximize the impact of this strategy, however, a clear understanding is needed to marry the inconsistent effects on urinary potassium and sodium and the “very impressive reduction” in hypertension with the modest BP reductions, he said. Still, the lack of adverse safety effects is reassuring.
“This is very important because when considering population use of salt substitute, the first thing that arises in every discussion is, ‘What about the risks of hyperkalemia?’ ” Neal said. “I think those risks are probably greatly overstated because they probably only apply to a small proportion of the population with severe kidney disease, most of whom would be aware they have severe kidney disease and should also avoid potassium-salt substitutes.”
Commenting for theheart.org | Medscape Cardiology, session co-chair Frank Ruschitzka, MD, University Hospital Zurich, Switzerland, said, “My take on salt is that it’s a bit overrated, the whole issue. I tell my patients not to add salt and to throw away the salt shaker and that’s it. This has a twist because there are a lot of potassium-sparing trials now ongoing, but whether that is a good thing, you tell me.”
“What they have shown is that the concept works, they embrace it,” he said. “These are modest decreases in blood pressure for a relatively short period, but I think it is a wonderful trial. It’s a nonpharmacological treatment that is not as fancy as throwing devices around, but I think that matters. It’s very important.”
Asked about the findings, ESC spokesperson and electrophysiologist Natasja De Groot, MD, PhD, Erasmus Medical Center, Amsterdam, the Netherlands, said, “I hope this congress really alerts people that this is possible and that we have to think of a way to generalize it.”
As to the practicality of implementation in other countries with differing economies and food policies, she said, “I think that has to be something which has to come from government to lower prices if you want to import a certain product. That will be the major issue because it must be affordable for all people. If the price is very high then people won’t buy it.”
Although the program is no longer ongoing, the price of the Liz salt substitute has fallen in the supermarket from $10 to $5, Miranda told theheart.org | Medscape Cardiology. The price for 1 kg of regular salt is 20 to 30 cents.
“Right now the market for this is very little, it’s not prescribed,” he said. “But if they see the market is larger, they are willing to reduce their costs.”
The study was funded by the National Heart, Lung, and Blood Institute/National Institutes of Health, Global Alliance for Chronic Diseases program. Miranda and De Groot report having no relevant financial disclosures. Neal reports research support from NuTek Salt and the Beijing Salt Industry Corp.
European Society of Cardiology (ESC) Congress 2019. Presentation 3181. Presented September 2, 2019.