High-Dose Thiamine Supplementation Improves Glucose Tolerance in Hyperglycemic Individuals: a Randomized, Double-Blind Cross-Over Trial

Purpose: To assess the effect of high-dose oral thiamine supplements on glucose tolerance in patients with impaired glucose metabolism. Methods: Twelve hyperglycemic subjects (10 cases of impaired glucose tolerance and 2 new cases of type 2 diabetes) completed this randomized, double-blind trial, where all participants received both placebo and thiamine capsules (3 × 100 mg/day) for 6 weeks in a cross-over manner. The main endpoint was changes in 2-h plasma glucose. Fasting plasma glucose and insulin, 2-h plasma insulin, the hemostatic model assessment of insulin resistance (HOMA-IR), renal function measurement and thiamin status were also evaluated at the commencement and completion of each treatment period. Results: Thiamine supplementation resulted in significant decrease in 2-h plasma glucose relative to baseline (8.78 ± 2.20 vs. 9.89 ± 2.50 mmol/l, p = 0.004), with no significant change in the placebo arm. Fasting plasma glucose and insulin, and HOMA-IR increased significantly from baseline after 6 weeks in the placebo arm (p = 0.003, p = 0.04 and p = 0.02, respectively). These variables did not change with thiamine supplementation. There were no significant changes in 2-h plasma insulin or renal function marker, within or between arms. Conclusion/interpretation: Supplementation with high-dose thiamine may prevent deterioration in fasting glucose and insulin, and improve glucose tolerance in patients with hyperglycemia. High-dose thiamine supplementation may prevent or slow the progression of hyperglycemia toward diabetes mellitus in individuals with impaired glucose regulation