Abstract
BACKGROUND: Despite the crucial role of thiamine in glucose and energy metabolism pathways, there has been no published study examining the impact of thiamine on energy metabolism in humans. OBJECTIVE: To assess the effects of thiamine supplementation on resting energy expenditure (REE) in individuals with hyperglycemia. METHODS: Twelve hyperglycemic patients completed this double-blind, randomized trial, where all participants received both thiamine (300 mg/day) and matched placebo for 6 weeks in a cross-over manner. REE was assessed by indirect calorimetry. Anthropometric measurements, fasting and 2-h plasma glucose, and glucose-induced thermogenesis were also assessed at the beginning and on the completion of each six-week phase. RESULTS: Participants consuming thiamine supplements experienced a significant decrease in the REE assessed at week six compared to the baseline [mean (SE): 1478.93 (73.62) vs.1526.40 (73.46) kcal/d, p = 0.02], and the placebo arm (p = 0.002). These results did not change significantly after adjusting for the participants' body weight and physical activity as potential confounders. Six-week intervention had no significant effect on the participants' body weight or waist circumference, in either supplement or placebo arms (all p values>0.05). However, correlation analysis highlighted significant positive relationships between the changes in REE, and those in fasting (r(s) = 0.497, p = 0.019) and 2-h plasma glucose (r(s) = 0.498, p = 0.018) during the six-week intervention period. CONCLUSION: Supplementation with high-dose thiamine may attenuate REE in patients with impaired glucose regulation. Our findings suggest that the impact of thiamine on REE may in part be explained by improved glycemic control. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12611000051943. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12611000051943.