Probiotics for Glycemic Control in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Abstract

Importance: Clinical trial evidence is inconsistent on whether probiotics are effective and safe for glycemic control for type 2 diabetes mellitus (T2DM).

Objective: To evaluate the effectiveness and safety of probiotics for glycemic control for T2DM through a systematic review. Data Sources: We searched PubMed, Embase, Cochrane databases, and trial registries up to February 2019.

Study Selection: We included randomized controlled trials (RCTs) in participants with prediabetes or T2DM. Eligible trials compared probiotics with no intervention/placebo/comparison probiotics, or compared synbiotics with prebiotics.

Data Extraction and Synthesis: Two reviewers independently screened titles and abstracts, full-texts, extracted data, and assessed the risk of bias. We performed meta-analyses using the random-effects model.

Main Outcome(s) and Measure(s): Primary outcomes were mean change in fasting blood glucose (FBG) and glycosylated hemoglobin (HbA1C) from baseline in short term (<12 weeks) and long term (≥12 weeks).

Results: We included 28 RCTs (1,947 participants). The overall risk of bias was either some concern or high. Probiotic group demonstrated greater reduction in FBG than placebo/no intervention group with a mean difference (MD) of -12.99 mg/dL (95% confidence interval (CI) -23.55 to -2.42) over the short term; and -2.99 mg/dL (95% CI -5.84 to -0.13) over the long term. The evidence for reduced HbA1C in the probiotics group at both short-term (MD -0.17, 95% CI -0.37 to 0.02) or long-term (MD -0.14, 95% CI -0.34 to 0.06) is less clear. We found similar findings in the meta-analyses comparing the effect of synbiotics versus prebiotics. No evidence of the difference between various types of probiotics was observed. No trials reported serious adverse events. Subgroup analyses showed a greater reduction in HbA1C in participants not receiving insulin therapy than those receiving insulin therapy (MD -0.34%, 95% CI -0.58 to -0.11). Furthermore, the effect of probiotics on the reduction of FBG was more pronounced in participants with FBG >130 mg/dL and those not receiving insulin therapy than their counterparts (p <0.01).

Conclusions and Relevance: Probiotics may have a glucose-lowering effect on T2DM participants. The effect appeared to be stronger in participants with poorly controlled diabetes and those not on insulin therapy.

Funding Statement: TR is a visiting scholar at Johns Hopkins Bloomberg School of Public Health. Her scholarship is funded by the Prince Mahidol Award Foundation under the Royal Patronage. The project received partial funding support from the Thailand Research Fund (RDG6150124).

Declaration of Interests: The authors declare that they have no competing interests.