Effect of probiotics at different intervention time on glycemic control in patients with type 2 diabetes mellitus: a systematic review and meta-analysis

Systematic review and meta-analysis of eight randomized controlled trials in adults with type 2 diabetes mellitus from multiple countries, including Iran, Brazil, Malaysia, Ukraine, and Greece. Across the active probiotic arms, 252 participants were randomized; the comparator groups included 255 participants.

Oral probiotic interventions were tested against placebo or usual care in adults with type 2 diabetes mellitus. The review evaluated short-term courses of 6 to 8 weeks and longer courses of 12 to 24 weeks; strain-specific dose and formulation details were not provided in the source packet.

Probiotics were associated with modest improvements in glycemic control in type 2 diabetes, with benefits for HbA1c, insulin, and HOMA-IR, but not fasting blood glucose or BMI. Compared with control, HbA1c decreased by MD = -0.33, 95% CI (-0.59, -0.07), p = 0.01. Insulin also improved, with SMD = -0.48, 95% CI (-0.74, -0.22), p = 0.0003, and HOMA-IR decreased by SMD = -1.36, 95% CI (-2.30, -0.41), p = 0.005. The authors suggested a time-related effect, with HbA1c reduction seen at 6 to 8 weeks and insulin/HOMA-IR improvements seen at both 6 to 8 weeks and 12 to 24 weeks.

The evidence base was small, with only eight RCTs and 507 total participants, limiting certainty. Probiotic strains, doses, and formulations were not consistently detailed in the source packet, and the included studies varied in intervention duration, which may increase heterogeneity and limit generalizability. The authors also noted the need for additional high-quality, large-scale trials.