Association Between Changes in Salt Intake and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized...

Excessive salt intake is a well-established, modifiable risk factor for hypertension and cardiovascular disease. Although reducing salt consumption lowers blood pressure (BP), the quantitative association across intake levels, subgroup differences, and the influence of salt-intake assessment methods remain uncertain.

To evaluate the association between salt-intake levels and BP across randomized controlled trials using predefined intake categories and to explore study-level continuous trends.

The PubMed, Embase, Cochrane Library, Web of Science, CINAHL, China Knowledge Network, Wanfang, China Science and Technology Journal Database (VIP), and Sinomed databases were searched from inception to December 2024, without language restrictions.

Two reviewers independently screened records using prespecified PICOS criteria, extracted study characteristics and outcomes (systolic and diastolic BPs), and assessed risk of bias with the RoB2 tool. Discrepancies were resolved by discussion or third-reviewer adjudication. Salt was used as the primary exposure metric (measured in grams per day; conversion: 1 g sodium = 2.54 g salt).

Random-effects meta-analyses compared standardized intake categories (high >15 g d-1; moderate 5-15 g d-1; low <5 g d-1). Prespecified study-level meta-regression was conducted as an exploratory assessment of continuous trends. Subgroup and sensitivity analyses considered salt sensitivity, age, intervention duration, comorbid conditions, geographic region, publication year, and potassium handling. Publication bias diagnostics were performed where applicable.

Across 43 randomized controlled trials (1983-2024), higher amounts of salt intake were associated with higher BP, whereas lower intake was associated with larger BP reductions, demonstrating a graded association across intake categories. Exploratory study-level continuous trends were not statistically significant, consistent with residual heterogeneity, exposure measurement error, and adherence variation. These findings support individualized salt-reduction strategies and robust public-health measures, including food reformulation and national salt-reduction programs, to reduce the burden of hypertension and cardiovascular disease.

PROSPERO registration No. CRD42024617388.