Effects of Polyphenol Supplementation on Gut Microbiota Composition and Fecal Short-Chain Fatty Acids: 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 42280405 · doi:10.3390/nu18111762
What was done
A systematic review and random-effects meta-analysis was conducted across five databases through October 2023. Eligible studies were randomized controlled trials assessing oral polyphenol supplementation in adults reporting on gut microbiota composition, microbial diversity, or fecal short-chain fatty acids (SCFAs). Risk of bias was evaluated with Cochrane RoB 2, and evidence certainty was assessed using GRADE. Subgroup analyses examined polyphenol class, dose, duration, health status, and analytical methods.
What was found
Across 50 RCTs (n = 2,042), polyphenol supplementation significantly increased fecal butyrate concentrations (pooled SMD = 0.48; 95% CI: 0.32–0.64; I² = 58%). Total SCFAs increased in 70.6% of studies, acetate in 75%, and propionate in 71.4%. Supplementation was associated with increased relative abundance of Bifidobacterium (81.8% of studies), Akkermansia muciniphila (50%), and Faecalibacterium prausnitzii (45.5%), alongside decreases in Enterobacteriaceae and Clostridium spp. Alpha diversity increased in 66.7% of studies and beta diversity in 87.5%. Effects were generally stronger in individuals with metabolic disorders and in interventions lasting 12 weeks or more.
Why it matters
This synthesizes human trial evidence showing that dietary polyphenols consistently enhance butyrogenic fermentation and support beneficial gut commensals, clarifying their prebiotic-like actions in adults.
Limits
Moderate heterogeneity was observed for butyrate outcomes (I² = 58%), and many microbial taxonomic and diversity outcomes were reported as descriptive study proportions rather than pooled effect sizes. The abstract does not report whether these microbiome changes translate into clinical health improvements.
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