**4. Reference values for urinary water-soluble vitamins**

Urinary water-soluble vitamins can be used as potential biomarker not only for estimation of its intake but also evaluation for its nutritional status. The intervention study comprehensively investigated urinary water-soluble vitamin values in subjects consuming semi-purified diet with vitamin mixture for 7 days (Shibata et al., 2005). The study revealed the mean values and ranges for each water-soluble vitamin except vitamin B12 in the subjects with vitamin mixture based on DRIs for Japanese. Based on these results, we propose the reference values for urinary water-soluble vitamins to show adequate nutritional status in Table 7. When urinary excretion of some vitamins is lower than the lower reference value, subject may not intake its vitamin enough for DRIs. When urinary vitamin is higher than the upper value, subject may intake its vitamin supplement. These reference values may be useful for first screening to check one's vitamin nutritional status and vitamin supplement intake.


aUrinary excretion for each vitamin corresponds to thiamin for vitamin B1, riboflavin for vitamin B2, 4-PIC for vitamin B6, the sum of nicotinamide, MNA, 2-Py and 4-Py for niacin equivalent, the sum of reduced and oxidized ascorbic acid and 2,3-diketogluconic acid for vitamin C.

Table 7. Proposed reference values for urinary water-soluble vitamins in adults.

### **5. Conclusion**

Recent studies have induced great advances for urinary water-soluble vitamins as biomarkers for its intakes. Measuring urinary water-soluble vitamin levels can be the good approach for assessing dietary vitamin intake in groups, and for simply evaluation of its nutritional status in individuals. However, there is limitation for its use; urinary vitamins have not been suitable biomarker to estimate its intake in individuals yet. More accurate estimation of the dietary intake of water-soluble vitamins based on urinary excretion requires additional, precise biological information such as the bioavailability, absorption rate, and turnover rate. Next step in this type of study will be to determine whether vitamin contents in spot urine sample is used to assess water-soluble vitamin intakes in groups.
