Effect of Salt Reduction Interventions in Lowering Blood Pressure and Salt Intake in Zhejiang Province, China, 2017–2021: A Randomized Controlled Trial

Background: Addressing high-salt diets in China through interventions can significantly reduce blood pressure (BP) and the associated health risks. Objective: This study aims to evaluate the effectiveness of a comprehensive salt reduction intervention implemented across counties in Zhejiang Province, focusing on system establishment, extensive publicity, and targeted population interventions. Methods: The Salt Reduction and Hypertension Prevention Project was initiated in Zhejiang Province. Cross-sectional surveys were conducted before the intervention and after. The research commenced in 2017 with a baseline survey involving 7512 participants from five counties. Four counties were randomly selected for the intervention, implementing a multifaceted salt reduction strategy, while one county served as a reference without any intervention. The primary outcomes measured were changes in BP and 24 h urinary sodium and potassium excretion. Results: Following the intervention, 24 h urinary potassium excretion experienced a significant increase, rising from 1441.3 (SD 681.9) to 1676.9 (SD 931.4) mg per day, p < 0.001. Utilizing a linear mixed-effects model, the adjusted net difference in urinary sodium changes was calculated to be 394.1 mg per day (95% CI, 133.2 to 655.0) (p = 0.003). There was a notable reduction in systolic blood pressure (SBP) from 131.2 (SD 19.2) to 129.8 mmHg (SD 18.0), and diastolic blood pressure (DBP) also decreased from 80.8 (SD 10.8) to 78.9 mmHg (SD 10.2), p < 0.001. The adjusted net differences for SBP and DBP between the intervention and reference groups were 1.3 (95%CI, 0.5 to 2.1) and 1.4 mmHg (95%CI, 0.9 to 2.0), respectively, p < 0.001. Conclusions: The findings indicate that a multi-sectoral approach, combined with extensive public awareness initiatives and precisely targeted interventions, can significantly increase urinary potassium excretion and reduce sodium and blood pressure.