A 5-day fluoride (F) balance experiment in which an experimental diet was prepared from a combination of everyday food products was conducted in 11 adult females in order to investigate F metabolism in the body, mainly with respect to obtaining basic data related to the application of F to caries prevention. Fecal and urinary samples were collected in a metabolic laboratory facility from the first day of the experiment until day 5. Analytical assays of F, such as Ca, P, and trace elements (Zn, Cu, Se, and Fe) were carried out and the balances of the respective substances investigated. The following conclusions were obtained.
1) The mean daily F intake value for the experimental diet was found to be 359µg, with the range being 304-439µg. F balance was investigated using fecal and urinary F excretions. It was found that approximately 87.8% of the F was absorbed by the body, of which about 50.2% was excreted via the urine, resulting in a retention rate of about 43.9%. Investigation of daily fluctuations in urinary F excretion revealed no significant differences in the mean values. A positive, significant correlation was found between F intake and F absorption, and a negative, significant correlation was observed between urinary F excretion and F retention.
2) When the relationship between F and Ca was investigated, it was found that positive, significant correlations existed between F intake and Ca intake, F intake and urinary Ca excretion, fecal F excretion and urinary Ca excretion, and F absorption and Ca intake. A significant negative correlation was found between F absorption and urinary Ca excretion.
When the relationship between F and P was examined, significant positive correlations were found between F intake and P intake, F intake and urinary P excretion, fecal F excretion and fecal P excretion, and F absorption and P intake. A significant negative correlation was found between fecal F excretion and P retention.
3) Investigation of the relationships between F balance and the balances of Zn, Cu, Se and Fe revealed significant correlations for all 4 elements. This was judged to result from the correlation between F intake and absorption and the intakes of the 4 elements. Significant positive correlations were found between fecal F excretion and the fecal excretions of Cu, Se, and Fe.
4) From the above, it was possible to obtain basic information related to the retention of F in foods when F is used for the prevention of caries. A strong relationship was found between F metabolism and the metabolism of Ca and P. The results of the study suggested a certain degree of relationship between F metabolism and Zn, Cu, Se, and Fe metabolism, so it is thought that further research is required in order to clarify these findings.