The effect of oral synbiotics on the gut microbiota and inflammatory biomarkers in healthy adults: a systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 38341803 · doi:10.1093/nutrit/nuae002
What was done
A systematic review and meta-analysis of randomized controlled trials was conducted across Scopus, PubMed, Web of Science, ScienceDirect, MEDLINE, CINAHL, and Cochrane Library to evaluate the effects of oral synbiotics in healthy adults. Primary outcomes were alterations in gut microbiota or intestinal permeability. Secondary outcomes included short-chain fatty acids, gut microbiota diversity, and inflammatory biomarkers. Continuous outcomes were pooled using restricted maximum likelihood random-effects models as standardized mean differences (SMD) or weighted mean differences (WMD). Twenty-seven articles representing 26 studies (n = 1319) met inclusion criteria.
What was found
Meta-analyses of 16 studies demonstrated that synbiotics significantly increased Lactobacillus cell count (SMD 0.74; 95% CI, 0.15 to 1.33; P = 0.01) and propionate concentration (SMD 0.22; 95% CI, 0.02 to 0.43; P = 0.03) compared to controls. Non-significant trends were observed for Bifidobacterium relative abundance (WMD 0.97; 95% CI, 0.42 to 2.52; P = 0.10) and cell count (SMD 0.82; 95% CI, 0.13 to 1.88; P = 0.06). There were no statistically significant differences in alpha-diversity, acetate, butyrate, zonulin, IL-6, CRP, or endotoxins.
Why it matters
This review shows that synbiotic supplementation can selectively increase Lactobacillus abundance and propionate levels in healthy adults. However, it does not meaningfully alter overall microbiome diversity, gut permeability markers, or baseline systemic inflammation in healthy populations.
Limits
Included trials had substantial heterogeneity in the specific strains, prebiotic types, doses, and intervention durations used. Data for meta-analysis could only be pooled from 16 of the 26 identified studies, and the lack of change in inflammatory or permeability markers may reflect baseline floor effects in healthy cohorts.
Cited by
- supports Probiotic and prebiotic supplementation supports a healthy gut microbiome.