A Meta-Analysis of Effect of Dietary Salt Restriction on Blood Pressure in Chinese Adults

Abstract

The aim of this study was to estimate the effects of dietary salt reduction on blood pressure (BP) in Chinese adults and the effects of China-specific cooking salt-reduction strategies (the use of salt substitutes and salt-restriction spoons). The PubMed and China National Knowledge Infrastructure databases were searched for studies satisfying the search criteria. Outcomes extracted from each included study were 24-h urinary sodium excretion, salt (sodium chloride) intake, and BP before and after dietary salt lowering. A random-effects meta-analysis was performed, and results were evaluated for evidence of publication bias and heterogeneity. Because most studies aggregated results for hypertensive and normotensive participants, estimates were made for hypertensive participants only and for hypertensive and normotensive participants combined. Six salt-restriction experiment studies (3,153 participants), 4 cooking salt-restriction spoon studies (3,715 participants), and 4 cooking salt-substitute studies (1,730 participants) were analyzed. In salt-restriction experiment studies, the pooled estimate of mean change in 24-h urinary sodium excretion in hypertensive participants was -163.0 mmol/day (95% confidence interval [CI]: -233.5 to -92.5 mmol/day), which was associated with a mean reduction of -8.9 mm Hg (95% CI: -14.1 to -3.7 mm Hg) in systolic BP. Each 1.00-g dietary salt reduction in hypertensive participants was associated with a reduction of 0.94 mm Hg in systolic BP (95% CI: 0.69 to 1.03 mm Hg). These systolic BP reductions in hypertensive participants were 1.71 times greater compared with the mixed hypertensive and normotensive group. Salt-restriction spoon studies demonstrated a 1.46-g decrease in daily salt intake level. The effect of salt-substitute use on systolic BP control was substantial among the hypertensive participants (-4.2 mm Hg; 95% CI: -7.0 to -1.3 mm Hg), but the change did not reach statistical significance in hypertensive and normotensive participants combined (-2.31 mm Hg; 95% CI: -5.57 to 0.94 mm Hg). Salt restriction lowers mean BP in Chinese adults, with the strongest effect among hypertensive participants. Future studies of salt-restriction strategies should be report results stratified by hypertension status and adjust for medication use.