Reduce your blood pressure: cut down on dietary salt or replace it with diet salt?

According to a Chinese study (DECIDE-Salt) carried out over a 2-year period in institutionalized elderly subjects, replacing dietary salt (sodium chloride) with a substitute (potassium chloride) is more effective in reducing blood pressure, particularly systolic pressure, and preventing cardiovascular events than reducing dietary salt intake. However, in elderly patients, who are often taking multiple medications, it is important to bear in mind the possible risks of substituting these potassium chloride-based "false salts" or "diet salts" sold over the counter in pharmacies, in the absence of recent blood tests (blood ionogram, plasma creatinine). The use of "false salts" if effective in controlling blood pressure must therefore be supervised by the pharmacist and attending physician.
The aim of the DECIDE-Salt study

Reducing sodium intake and salt replacement (or substitution) have been described as interesting non-drug methods for reducing blood pressure. However, data on this second option are scarce in the elderly. Moreover, the associated risk of excess potassium (hyperkalemia) is poorly established. It was therefore of interest to carry out a study comparing the efficacy and safety of the two strategies in elderly adults living in specialized residences.

Methodology

The DECIDE-Salt study was carried out over a two-year period in 48 Chinese establishments, randomly assigned to 4 modalities: maintenance of usual table salt or replacement, with or without gradual reduction of salt or substitute quantities....
Residents in the 2 "replacement" groups received a salt substitute (62.5% sodium chloride, 25% potassium chloride, 12.5% flavoring), while those in the "control" groups consumed usual salt (100% sodium chloride). The cooks were not to use any other sources of salt during the two years of the study. For the gradual reduction in salt consumption or substitute, the aim was to achieve a 40% reduction in initial consumption by the end of the study, at a rate of 5 to 10% every 3 months. Residents with excess potassium in the blood (hyperkalemia) were excluded from the study. Follow-up at 6, 12, 18 and 24 months was carried out.




Study results

This study included 1612 participants (mean age: 71 years; 76.3% men); of these, 62.1% were hypertensive, 29.1% had had a stroke or had coronary heart disease, and 19.4% had non-vascular health problems. The mean values of Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) at study entry were 137.5 and 80.5 mm Hg.
In establishments where salt substitution (sodium chloride) was carried out, mean SBP was lower than in those who continued to consume table salt: -7.1 mm Hg (from -3.8 to -10.5 mm Hg). On average, the effects were greater in women than in men. In establishments that gradually reduced salt consumption, no significant difference was observed (despite a trend over 2 years). Similarly, substituting salt with potassium chloride ("false salt" or "diet salt") led to a reduction in DBP of -1.9 mm Hg (-0.2 to -3.6 mm Hg) and a 40% reduction in cardiovascular events, but had no effect on mortality.
The salt substitute led to an increase in blood potassium levels and a decrease in sodium levels. As a result, hyperkalemia was observed in 7% of patients using salt substitutes, compared with 2.4% of those not using salt substitutes (i.e. a 3-fold increase), but without any serious clinical consequences.

For practical use....
These results are interesting to consider. They are based on well-known data such as variations in sodium and potassium intakes, whose role in controlling blood pressure is well established. The importance of reducing sodium intake is well established, and some also encourage higher potassium intakes through the diet.
In this study, dietary potassium intake proved to be more effective in reducing blood pressure than gradual salt reduction. However, we must be wary of the use of these "false" or "diet" salts sold over the counter in pharmacies, given the frequency of renal failure, a source of hyperkalemia, in elderly subjects, a fortiori hypertensives. What's more, these potassium chloride substitutes (instead of sodium chloride), often found in pharmacies under the name of "diet salt", don't taste very good, and in the absence of social security coverage, are quite expensive. These results, while demonstrating the benefits of potassium intake, must be applied with caution in elderly hypertensives, who often have complex prescriptions involving drugs that can interfere with potassium metabolism.
All in all, reduce and replace sodium chloride-based dietary salt, yes certainly! but rather with spices to give food more flavor!
Reference:
Yuan Y, et al. Salt substitution and salt-supply restriction for lowering blood pressure in elderly care facilities: a cluster-randomized trial. Nat Med. 2023 Apr 13.