Polyphenols, gut microbiota and short-chain fatty acids: meta-analysis of RCTs
Polyphenol supplementation significantly increased fecal butyrate concentrations (SMD = 0.48) across 50 RCTs in adults.
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What the study showed
The meta-analysis of 50 RCTs (n = 2042) showed a significant pooled effect on butyrate (SMD = 0.48; 95% CI: 0.32–0.64; I² = 58%). Acetate and propionate increased in the majority of individual studies, though pooled estimates for these outcomes are not reported in the abstract. A shift toward a more butyrogenic fermentation profile and increases in beneficial genera such as Bifidobacterium were also noted.
How it was done
Systematic review with random-effects meta-analysis; five databases searched through October 2023; risk of bias assessed with Cochrane RoB 2 and certainty of evidence with GRADE.
Risk of bias
Moderate-to-high heterogeneity (I² = 58% for butyrate) limits generalizability. The abstract does not report GRADE certainty ratings or subgroup results, precluding full evaluation of evidence quality.
What this study does NOT prove
One cannot conclude that increased fecal butyrate translates into measurable clinical benefits for any specific health condition.
In clinical practice
The butyrate effect is statistically significant, but SMD ≈ 0.48 with considerable heterogeneity warrants clinical caution. Polyphenol class, dose, duration, and health status were examined as moderators, but those results are unavailable from the abstract alone.
Limitations
Moderate-to-high heterogeneity (I² = 58% for butyrate) limits generalizability. The abstract does not report GRADE certainty ratings or subgroup results, precluding full evaluation of evidence quality.
Technical appendix
Version history
- 1.0 · 2026-08-18 — Auto-generated under Evidence Standard v1.0
Paid access: structured summary from public metadata; consult the original study at the source.