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A population-based salt-substitution strategy slashes hypertension risk

ESC Congress News 2019 - Paris, France

A simple strategy for reducing salt intake on a population scale halved the number of people developing hypertension. This startling statistic was just one of the findings reported by Professor Jaime Miranda (Universidad Peruana Cayetano Heredia, Lima, Peru) in a Hot Line Session yesterday.

Hypertension
Risk Factors and Prevention


Reducing blood pressure (BP) is key to reducing the risk of heart disease and stroke, and it has been known for decades that reducing sodium intake and increasing potassium can lead to reduced BP. The health threat of salt is such that World Health Organization Member States agreed to a reduction of 30% in global salt consumption by 2025.1 “Public health interventions, such as limiting the salt content of processed foods, are valuable steps towards this goal,” says Prof. Miranda. “But they take time. We wanted to do something quicker and simpler to reduce salt intake on a wide scale.”

esc_presentation_a_population_based_salt_substitution.jpgBasing their study in six villages in Tumbes, Peru, where the main salt intake was due to addition during cooking, Prof. Miranda’s team evaluated the effects of offering a low-sodium salt (‘Salt Liz’; 75% sodium and 25% potassium) to households, street vendors and food stores to replace 100% sodium salt. Interestingly, the salt was introduced via a social marketing strategy on the grounds of being highly desirable, rather than being healthy, explains Prof. Miranda. “We knew that if we said it was a healthy option, people would assume that it would taste bland and would not be interested in using it.” A randomised trial was neither feasible nor ethical, so a stepped-wedge design was employed, involving incremental initiation of villages for salt substitution at 5-month intervals and using the non-recruited villages at each stage as the control group. BP was measured at baseline, again every 5 months, at each new initiation, and at the end of the trial. The trial, which involved 2,376 participants, continued for three years (2014–2017).

Salt substitution led to an average population-wide reduction of 1.23 mmHg (95% confidence interval [CI] 0.38–2.07) in systolic BP and of 0.72 mmHg (95% CI 0.10–1.34) in diastolic BP.

“On the surface, these appear to be modest reductions in BP,” says Prof. Miranda. “But this is on a population-wide scale, including patients at all levels of hypertension risk. Studies have shown that a decrease of as little as 2 mmHg in systolic BP can translate into reductions in stroke mortality and cardiovascular mortality by 10% and 7%, respectively. So the benefits for the population are actually enormous.” This is particularly true for individuals without hypertension. “There was a massive effect of salt substitution on preventing the development of hypertension, with a 55% reduction in the risk of hypertension among those hypertension-free at baseline (p<0.001). And in high-risk patients, including those with hypertension at baseline and older people, the absolute reductions in BP were at least double those seen in lower-risk subgroups.”

How did the group know that Salt Liz was being used by people and not just left in the cupboard? “We tested urinary levels of sodium and potassium in a random sub-sample of the group at baseline and at the end of the study,” Prof. Miranda explains, “and confirmed that the changes were in line with use of the salt substitute.” There is a word of caution here regarding the use of the sodium/potassium salt in people with kidney disease, who should be managed closely by their renal consultant.

“Our salt-substitution approach proved to be an extremely effective way of reducing salt intake and hypertension across communities,” says Prof. Miranda. “We think that it could be applied in other societies, although the impact may differ depending on societal behaviour. For example, in our study, the prime source of salt intake was through cooking. In other societies, where salt is consumed mainly via processed foods, the effect of replacing household salt is likely to be smaller across all groups. But the benefits will still be evident.” He concludes that, “Multiple strategies are required to reduce salt consumption in the general public and our population-based method could make a major contribution to these efforts to reduce BP and impact on stroke and cardiovascular mortality.”

 

 

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References

www.who.int/news-room/fact-sheets/detail/salt-reduction

Notes to editor

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ESC Congress is the world’s largest and most influential cardiovascular event contributing to global awareness of the latest clinical trials and breakthrough discoveries. ESC Congress 2019 takes place 31 August to 4 September at the Paris Expo Porte de Versailles, Paris - France. Explore the scientific programme