Research synthesisModerate evidenceMixed effect size3 studies · 3 beneficial · 0 neutral · 0 harmful
Across 3 studies, all reported beneficial effects on HOMA-IR, with effect sizes ranging from small to large. Two meta-analyses found large reductions (WMD -2.56, 95% CI -3.82 to -1.30; MD -1.71), while one RCT in metabolic syndrome patients found a small reduction that was not significantly different from an unfermented milk control. Median study duration was 84 days, but dose data are limited (only one study reported 180 mL/day). Evidence is preliminary and subject to publication bias.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Additionally, one RCT showed improvement but not superior to unfermented milk control, suggesting the effect may not be specific to kefir.
Generated Jun 14, 2026