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

  • 2025-09-29
  • Nutrition journal 24(1)
    • Kai Zhuang
    • Huanhuan Luo
    • Muhuang Zeng
    • Sze Chun Leo Chan
    • Meiting Gong
    • Yunhan Wang

Study Design

Type
Meta-Analysis
Sample size
n = 633
Population
older adults (individuals aged ≥ 60 years); 29 RCTs involving 1,633 participants
Methods
Meta-analysis of randomized controlled trials (RCTs) published up to May 2025; PubMed, Embase, Cochrane Library, and Scopus were searched, and standardized mean difference (SMD) was used as the effect measure

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.

Supplementary Information: The online version contains supplementary material available at 10.1186/s12937-025-01218-1.

Keywords: Gut microbiota; Meta-analysis; Older adults; Prebiotics; Probiotics; RCT; Synbiotics.

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