Salt substitute: An effective way to lower salt intake and blood pressure

The DECIDE-Salt trial assessed dietary sodium-reduction strategies over 2 years in residential care patients, targeting significant reductions in systolic blood pressure.

Salt substitute reduced blood pressure and cardiovascular events, with decent safety

The real-world DECIDE-Salt trial looked at the efficacy and safety of different dietary sodium-reduction strategies over 2 years in patients living in residential care facilities. Whereas a salt reduction was not able to lower the salt intake, a salt substitute proved to be highly beneficial; salt intake was lowered, which translated into a significant reduction in systolic blood pressure (BP)1.

Lowering dietary sodium intake can reduce blood pressure, but practical strategies to reduce salt intake are not well established. The DECIDE-Salt (NCT03290716) study, which included 1,612 individuals (≥ 55 years) from 48 residential care facilities in China whose mean baseline BP was 138.6/81.4 mmHg, explored different ways of salt reduction regarding the influence on BP (i.e. primary endpoint) and cardiovascular events (i.e. secondary endpoint). 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 that consisted of 62.5% NACL, 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 on systolic blood pressure.

Salt substitute was associated with an increase in mean serum potassium and the incidence of biochemical hyperkalaemia compared with usual salt

Notably, a 40% reduction was seen in the relative risk of major CV events (HR 0.60; 95% CI 0.38¬–0.96; P=0.0318) in the salt substitute group. Again, there was no influence of progressive restriction of salt/substitute on 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, 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 hyponatremia,” 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 salt substitute compared with usual salt (RR 0.23; 95% CI 0.06–0.89; P=0.0334). 

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

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.