Salt substitutes: a successful strategy to improve blood pressure

In the real-world DECIDE-Salt trial, a salt substitute was a safe and effective way to lower salt intake that led to a significant reduction in systolic blood pressure (BP) [1]. In contrast, a stepwise approach to reduce salt in the diet failed to lower salt intake.

The DECIDE-Salt study (NCT03290716) investigated strategies to lower dietary sodium intake, which might improve BP control. The study included 1,612 individuals (≥55 years) from 48 residential care facilities in China whose mean baseline BP was 138.6/81.4 mmHg and explored different ways of salt reduction regarding the influence on BP (i.e. primary endpoint) and cardiovascular events (i.e. secondary endpoint). Details of the study design were previously published [2]. Safety outcomes included hyperkalaemia, hypokalaemia, and impaired renal function.

In one group, usual salt was replaced by salt substitute in facility kitchens; in the other group, either salt or salt substitute was step-by-step reduced to 60% of the original salt content at baseline. Baseline characteristics of the participants were comparable in both groups. Prof. Yangfeng Wu (Peking University Clinical Research Institute, China) explained that a commercial salt substitute was used consisting of 62.5% NaCI, 25% KCL, 12.5% dried food flavourings, and traces of amino acids. Usual salt consisted of over 99% NaCl. Both were Iodine-fortified and provided to the facilities.

Compared with usual salt, the salt substitute led to reductions in mean systolic BP (-7.14 mmHg; 95% CI -10.49 to -3.79; P<0.0001) and mean diastolic BP (-1.91 mmHg; 95% CI -3.58 to -0.24; P=0.0251). In contrast, there was no significant influence of restricted supply versus usual supply of sodium on systolic BP.

Notably, a 40% reduction was seen in the relative risk of major CV events in the salt substitute group (HR 0.60; 95% CI 0.38­–0.96; P=0.0318). Again, progressive restriction of salt/substitute did not influence this outcome. Mean 24-hour urinary sodium excretion in participants with progressive restriction of salt/substitute supply was not significantly reduced (-5.7 mmol; 95% CI -24.7 to 13.3; P=0.5551) compared with usual supply. Neither salt reduction strategy influenced the risk of total mortality.

Moreover, the salt substitute was associated with an increase in mean serum potassium and the incidence of biochemical hyperkalaemia compared with usual salt (relative risk [RR] 2.67; 95% CI 1.18–6.05; P=0.0189). “We noted a higher risk of hyperkalaemia but no increased risk of hyponatraemia,” Prof. Wu explained. In addition, only 2 patients had constantly elevated serum potassium levels, and there were no deaths attributed to hyperkalaemia. The risk of hypokalaemia was lower with the salt substitute compared with usual salt (RR 0.23; 95% CI 0.06–0.89; P=0.0334).

Prof. Wu concluded that the salt substitute reduced BP and cardiovascular events with decent safety. Although the salt substitute increased the risk of biochemical hyperkalaemia, no evidence of associated adverse clinical outcomes emerged. In contrast, stepwise restriction of salt/salt substitute supplied to facility kitchens did not meaningfully reduce sodium intake, and hence had no impact on BP or CV events.

1. 
   
   1. Wu Y. Impact of salt substitute and stepwise reduction of salt supply on blood pressure in residents in senior residential facilities: Main results of the DECIDE-Salt trial. Late-breaking trials in hypertension. ESC Congress 2021, 27–30 August.
   2. Jin A, et al. Am Heart J 2020;226:198–205.

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Posted on 26 October, 2021