This meta-analysis synthesized 29 RCTs (n = 1,633; ≥60 years) to evaluate how probiotics, prebiotics, and synbiotics (PPS) affect gut microbiota, SCFAs, and inflammation in older adults. Prebiotics and probiotics increased Bifidobacterium abundance (prebiotics SMD = 1.09; probiotics SMD = 0.40), while synbiotics elevated specific strains (e.g., B. angulatum, B. longum, B. breve). Probiotics improved alpha diversity (Shannon index SMD = 0.76); synbiotics raised Lactobacillus casei abundance (SMD = 0.75) and reduced Pseudomonas (SMD = −0.55). Anti-inflammatory effects included higher IL‑10 (prebiotics SMD = 0.61) and lower IL‑1β (prebiotics SMD = −0.39) and TNF‑α (synbiotics SMD = −0.36). Synbiotics also increased valeric (SMD = 0.50) and acetic acid (SMD = 0.62). Implication: PPS can beneficially modulate microbial composition, diversity, and inflammatory milieu to support healthy aging. [147+ source]