Impact of Single and Multi-Strain Probiotic Supplementation on Glycaemic Control in Type 2 Diabetic Patients: A Comparative Meta-Analysis

Probiotics, whether consisting of a single strain or multiple strains, are attracting growing interest in the management of type 2 diabetes mellitus (T2DM). However, their efficacy remains a matter of controversy and requires careful consideration. Accordingly, this meta-analysis aimed to compare the efficacy of single-strain to that of multi-strain probiotics supplementation on glycated haemoglobin (HbA1c) and fasting blood glucose (FBG) levels in adults with T2DM. Nineteen articles published between 2017 and 2024 obtained from 4 databases (Cochrane, Web of Science, Scopus, and PubMed) were included. These interventions, conducted in a total of 1159 participants, lasted from 6 to 24 weeks and were based on clearly identified probiotic formulations, with assessments of HbA1c and FBG. The results showed that, overall, probiotic supplementation had no significant effect on HbA1c (−0.24%; 95% CI [−0.76; 0.27]; p = 0.36), although a trend towards reduction was observed for single-strain formulations (−0.57%; p = 0.05). Regarding FBG, only the multi-strain group showed a significant reduction (−0.76; 95% CI [−1.18; −0.34]; p < 0.001), while the effect of the single-strain formulation was not significant. The comparison between the two formulations (Wald test) showed that there was no significant difference (p ≤ 0.05). However, high heterogeneity (I2 > 75%) and variable strains/doses limit confidence in these findings.