Urinary Water-Soluble Vitamins as Potential Nutritional Biomarkers to Assess Their Intakes

To determine micronutrient intake by dietary assessment is difficult because of high variations in habitual micronutrient intake. A nutritional biomarker can be an indicator of nutritional status with respect to intake or metabolism of dietary constituents. Recent validation studies have developed the urinary compounds as nutritional biomarkers to estimate nutrient intakes, and urinary nitrogen and sodium have been well established as nutritional biomarkers. Recent studies have conducted to establish urinary water-soluble vitamins as nutritional biomarkers to assess their intakes, and made the following findings to contribute to the establishment and effective use of urinary water-soluble vitamins as potential nutritional biomarkers. Only urinary vitamin B12 content reflects urine volume but not its intake. Eight of nine water-soluble vitamin levels in 24-hr urine increase in dose-dependent-manner, and are strongly correlated with vitamin intakes. Each urinary water-soluble vitamin level, except for vitamin B12, is positively correlated with the mean intake over the recent 2-4 days in free-living children, young and elderly. These findings suggest that urinary water-soluble vitamins can be used as nutritional biomarkers to assess their mean intakes in groups. Based on previous findings, the reference values for urinary water-soluble vitamins are proposed to show adequate nutritional status.