Effects of probiotics, prebiotics, and synbiotics on gut microbiota in older adults: a systematic review and meta-analysis of randomized controlled trials

Abstract

BACKGROUND: There is a lack of evidence on microbial compositions and associated metabolic changes in probiotics, prebiotics, or synbiotics (PPS) in older adults. OBJECTIVE: This meta-analysis aims to evaluate the effects of PPS on gut microbiota composition, short-chain fatty acids (SCFAs), and inflammatory markers in older adults. METHODS: PubMed, Embase, Cochrane Library, and Scopus databases were searched for randomized controlled trials (RCTs) published up to May 2025. RCTs were included if they examined microbiome-related outcomes in individuals aged ≥ 60 years following PPS interventions. The Cochrane Risk of Bias Tool was adopted for Quality appraisal. Meta-analysis was performed in RevMan 5.3, with standardized mean difference (SMD) as effect measures. RESULTS: 29 RCTs were included, involving 1,633 participants. PPS supplementation notably increased Bifidobacterium abundance (prebiotics: SMD = 1.09; probiotics: SMD = 0.40), whereas synbiotics showed no overall effect but enhanced the abundance of specific strains (B. angulatum, B. longum, B. breve). Probiotic supplementation enhanced microbial diversity (Shannon index: SMD = 0.76), while synbiotics increased Lactobacillus casei abundance (SMD = 0.75) and reduced Pseudomonas levels (SMD = -0.55). For inflammatory markers, prebiotics increased IL-10 levels (SMD = 0.61) and reduced IL-1β (SMD = -0.39), whereas synbiotics reduced TNF-α (SMD = -0.36). Synbiotic supplementation enhanced valeric acid (SMD = 0.50) and acetic acid levels (SMD = 0.62). CONCLUSION: PPS interventions demonstrated potential benefits for older adults by increasing beneficial bacteria such as Bifidobacterium and Lactobacillus casei, reducing harmful genera like Pseudomonas, improving anti-inflammatory responses, and enhancing the production of SCFAs.

Topics & Concepts