Efficacy of synbiotic interventions on blood pressure: a systematic review and meta-analysis of clinical trials

The present systematic review and meta-analysis aimed to evaluate the effect of synbiotic interventions on blood pressure levels in adults. A systematic literature search was conducted in the databases of MEDLINE, Scopus, Web of Science, and Cochrane through March 2020 to identify all randomized control trials (RCTs) investigating the effects of synbiotic interventions on blood pressure parameter, including systolic (SBP) and diastolic blood pressure (DBP). Grading of Recommendations Assessment, Development and Evaluation (GRADE) scale was used to assess the certainty of evaluated outcomes and determine the strength of recommendations. Eleven RCTs were included in the meta-analysis. Synbiotic interventions significantly reduced SBP (−3.02 mmHg; 95% CI: −4.84, −1.21; <i>I</i>² = 55%) without changing DBP levels (−0.57 mmHg; 95% CI: −1.78, 0.64; <i>I</i>² = 50%). Subgroup analyses revealed that the SBP-lowering effects of synbiotic interventions were more pronounced wherein trials were longer (≥12 weeks), synbiotic interventions were administrated as a supplement, and participants were younger (&lt;50 years old). Also, a significant improvement in both SBP and DBP levels was evident in subgroups with a lower (&lt;30 kg/m²) body mass index. Synbiotic interventions may significantly improve SBP levels in adults.