The effects of SCFAs on glycemic control in humans: a systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 35388874 · doi:10.1093/ajcn/nqac085
What was done
Authors conducted a systematic review and random-effects meta-analysis of randomized controlled trials evaluating the effects of short-chain fatty acids (SCFAs: acetate, propionate, butyrate, or vinegar) on glucose and insulin outcomes compared to placebo in adults. Databases (CENTRAL, Embase, PubMed, Scopus, Web of Science) were searched through December 7, 2021. Categories with 3 or more studies were meta-analyzed.
What was found
Across 43 papers reporting 46 studies (n = 913 total participants; 44 studies included in meta-analysis), acute vinegar intake significantly reduced acute glucose response in individuals with impaired glucose tolerance or type 2 diabetes (SMD -0.53; 95% CI, -0.92 to -0.14; n = 67) and in healthy volunteers (SMD -0.27; 95% CI, -0.54 to 0.00; n = 186). Meta-analyses for acute acetate, as well as acute and chronic propionate, showed no significant effect. Butyrate and mixed SCFAs also had no effect on blood glucose or insulin.
Why it matters
Despite strong mechanistic interest in SCFA production from dietary fiber for metabolic health, direct SCFA supplementation shows no clear benefit for glycemic control, and vinegar only produces modest, low-certainty acute glucose reductions.
Limits
The total sample size was small across many distinct subgroups (aggregate n = 913 across 46 studies). The authors identified substantial heterogeneity, high risks of bias, and evidence of publication bias, rendering the overall evidence very uncertain.
Cited by
- contradicts Soluble fermentable fiber serves as fuel for the gut microbiome and produces short-chain fatty acids like butyrate and propionate, which show positive metabolic health benefits in randomized controlled trials.