Effects of Probiotics and Synbiotics Supplementation on Blood Pressure in Adults with Prediabetes and Type 2 Diabetes Mellitus: A Grade-Assessed Systematic Review and Dose-Response Meta-Analysis.

Prediabetes and type 2 diabetes mellitus (T2DM) are closely linked with increased risk of hypertension, contributing significantly to cardiovascular complications. While probiotics and synbiotics have shown potential benefits in metabolic health, their specific effects on blood pressure (BP) regulation in this population remain unclear. This study aims to evaluate the impact of probiotics and synbiotics supplementation on BP control in adults with prediabetes and T2DM, addressing this critical knowledge gap. A comprehensive search was conducted on online databases from their inception to January 2025 to identify relevant randomized controlled trials (RCTs). Data were extracted from selected studies. The overall effect size was determined using weighted mean differences (WMD) with 95% confidence intervals (CIs) through a random-effects model. All statistical analyses were carried out using STATA software. The pooled analysis of 17 RCTs (19 effect sizes) with 1,281 participants (646 cases and 635 controls) showed that probiotics and synbiotics supplementation led to a significantly reduction in both systolic BP (WMD: -3.27 mmHg, 95% CI: -5.38 to -1.16, p = 0.002), and diastolic BP (WMD: -1.78 mmHg, 95% CI: -2.61 to -0.95, p < 0.001). The GRADE assessment rated the quality of evidence for SBP as moderate due to significant heterogeneity, which resulted in serious inconsistency; however, no other major limitations were identified. In comparison, the quality of evidence for DBP was rated as very high. This meta-analysis suggests that supplementation with probiotics and synbiotics can effectively reduce BP in adults with prediabetes and T2DM, highlighting their potential as an adjunctive strategy for BP management. Clinically, incorporating these supplements may offer a safe, accessible option to support traditional therapies and help reduce cardiovascular risk in this high-risk population.