Effect of thiamine supplementation on glycaemic outcomes in adults with type 2 diabetes: a systematic review and meta-analysis

Abstract

Background: Patients with type 2 diabetes mellitus (T2DM) have been shown to have thiamine deficiency. Dietary supplementation is an economic strategy to control blood glucose. Objective: To evaluate effectiveness of thiamine supplementation on glycaemic outcomes in patients with T2DM.

Methods: Eligibility criteria: Studies that assessed effect of thiamine supplementation in adults with T2DM which measured glycaemic outcomes-HbA1c, fasting blood glucose (FBG) and/or postprandial blood glucose (PPG) were included. Information sources: PUBMED, Tripdatabase, the Cochrane Central Register, National Institute of Health Clinical Database and Google Scholar were searched until December 2021 for RCTs. Risk of bias: It was assessed using standardised critical appraisal instruments from the Joanna Briggs Institute for RCTs. Synthesis of results: Where possible, studies were pooled in a meta-analysis. Results were presented in a narrative format if statistical pooling was not possible.

Results: Included studies: Six trials involving 364 participants. Synthesis of results: No significant beneficial effects were observed on glycaemic outcomes with 100-900 mg/day of thiamine or benfotiamine for up to 3 months (HbA1c: MD, -0.02%, 95% CI: -0.35 to 0.31; FBG: MD,-0.20 mmol/L; 95% CI: -0.69 to 0.29; PPG: MD, - 0.20 mmol/L, 95% CI: -2.05 to 1.65 (mean difference, MD)). There was a significant increase in high-density lipoprotein (HDL) (MD, 0.10; 95% CI: 0.10 to 0.20) at 3-month follow-up. Benfotiamine reduced triglyceride level (MD, -1.10; 95% CI: -1.90 to -0.30) in 120 mg/day dose as compared with placebo 150 mg/day, however this was not demonstrated in higher doses.

Discussion: Limitations of evidence: Inclusion of single-centre trials published only in English, small sample sizes of included studies, lack of trials investigating outcomes for same comparisons and varying follow-up periods. Interpretation: Thiamine supplementation does not affect glycaemic outcomes, however reduces triglycerides while increasing HDL. Multicentre well-designed RCT with higher doses of thiamine and a follow-up period of 1-2 years will provide better evidence.

Prospero registration number: CRD42020170520.

Keywords: General diabetes; Nutrition; Nutritional support.

Figure 1

PRISMA 2009 flow diagram for searching. PRISMA, Preferred Reporting Items for Systematic reviews and Meta-Analyses. *Consider, if feasible to do so, reporting the number of records identified from each database or register searched (rather than the total number across all databases/registers). **If automation tools were used, indicate how many records were excluded by a human and how many were excluded by automation tools. From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71.doi: 10.1136/bmj.n71. For more information, http://www.prisma-statement.org/

Figure 2

Effect of thiamine supplementation on HbA1c level at less than 3 months and at 3-month follow-up. HbA1c, glycosylated haemoglobin.

Figure 3

Effect on FBG at less than 3 months and at 3-month follow-up. FBG, fasting blood glucose.

Figure 4

Effect on HDL at less than 3 months and at 3-month follow-up. HDL, high-density lipoprotein.

Figure 5

Effect on LDL at less than 3 months and at 3-month follow-up. LDL, low-density lipoprotein.

Figure 6

Effect on triglycerides at less than 3 months and at 3-month follow-up.