Gut Microbiome Modulation in Type 2 Diabetes with Probiotics

Abstract

Introduction: Gut dysbiosis contributes to insulin resistance. Probiotics are widely used but evidence for glycemic benefit in type 2 diabetes (T2D) is inconsistent. Methods: Systematic review of 22 RCTs (n=1,389) comparing multi-strain probiotics (≥2 species, ≥10^9 CFU/day) versus placebo for ≥8 weeks in T2D. Primary outcome: HbA1c change. Secondary: fasting glucose, HOMA-IR, BMI. Results: Probiotics reduced HbA1c by -0.32% (95% CI -0.47 to -0.17, p<0.001), fasting glucose by -12.3 mg/dL (p=0.002), and HOMA-IR by -0.89 (p=0.01). No significant BMI change. Effect was larger when treatment duration ≥12 weeks and with ≥4 bacterial strains (Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus). Discussion: Probiotics modestly improve glycemic control, possibly via short-chain fatty acid production and reduced endotoxemia. Effect size is less than metformin but additive. Conclusion: Multi-strain probiotics for ≥12 weeks provide modest adjunctive glycemic benefit in T2D.