Effects of probiotics, prebiotics, and synbiotics on gut microbiota in older adults: a systematic review and meta-analysis of randomized controlled trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 41023690 · doi:10.1186/s12937-025-01218-1
What was done
A systematic review and meta-analysis searched PubMed, Embase, Cochrane Library, and Scopus through May 2025 for randomized controlled trials (RCTs). Studies were included if they evaluated the effects of probiotics, prebiotics, or synbiotics (PPS) on gut microbiota composition, short-chain fatty acids (SCFAs), and inflammatory markers in adults aged 60 years or older. Quality appraisal used the Cochrane Risk of Bias Tool, and meta-analyses computed standardized mean differences (SMD) using RevMan 5.3.
What was found
Across 29 RCTs with 1,633 participants, Bifidobacterium abundance increased with prebiotics (SMD = 1.09) and probiotics (SMD = 0.40), while synbiotics increased specific strains (B. angulatum, B. longum, B. breve). Probiotics increased microbial diversity on the Shannon index (SMD = 0.76). Synbiotics increased Lactobacillus casei (SMD = 0.75) and decreased Pseudomonas levels (SMD = -0.55). Prebiotics increased IL-10 (SMD = 0.61) and decreased IL-1β (SMD = -0.39), while synbiotics reduced TNF-α (SMD = -0.36). Synbiotics also increased valeric acid (SMD = 0.50) and acetic acid (SMD = 0.62).
Why it matters
This meta-analysis consolidates randomized evidence indicating that microbiome-targeted supplements can favorably reshape gut taxa, enhance short-chain fatty acid production, and reduce pro-inflammatory markers in older adults.
Limits
The abstract does not report confidence intervals, p-values, or statistical heterogeneity metrics (I²). Interventions aggregated diverse bacterial strains, prebiotic formulations, and dosages, and the average trial size was relatively small (approximately 56 participants per study).
Cited by
- supports Dietary fibers generally increase beneficial gut microbes such as Bifidobacterium and Lactobacillus, which produce short-chain fatty acids that support immune function.