Twenty-four-hour urinary thiamine as a biomarker for the assessment of thiamine intake

Objective: To investigate 24-h urinary thiamine as a potential biomarker for thiamine intake for use in validation studies to assess the validity of dietary intake data collected by self-reporting dietary methods. Subjects: Seven male and six female healthy participants living for 30 days in a metabolic suite under strictly controlled conditions consuming their usual diet as assessed beforehand from four consecutive 7-day food diaries kept at home. During the 30-day study, all 24-h urine specimens were collected, validated for their completeness and analysed for thiamine. Results: Thirty-day mean (±s.d.) calculated thiamine intake was 2.22±0.55mg/day. Thirty-day mean (±s.d.) urinary excretion of thiamine was 526.5±193.0 μg/day (24.7±8.10% of intake). There was a highly significant correlation between individuals' 30-day means of thiamine intake and their mean excretion level (r=0.720; P=0.006), where 1mg of thiamine intake predicted 268.2 μg of thiamine in urine. The correlations between intake and excretion remained significant when measurement from a single 24-h urine collection was used (r=0.56). Conclusion: Twenty-four-hour urinary thiamine can be used as a concentration biomarker for thiamine intake in dietary validation studies.