Abstract
We have clarified that the amounts of water-soluble vitamins excreted into urine closely reflect the surplus amount of water-soluble vitamins in the body, based on data from experiments involving rats and humans. We have also tried to calculate the cut-off values for preventing water-soluble vitamin deficiency and its resulting toxicity. Nutritional assessment using biomarkers is a persuasive approach, and facilitates easy adjustment of habitual dietary intake.