Fractional urinary fluoride excretion of young female adults during the diurnal and nocturnal periods.
OBJECTIVE
This study aimed to confirm a previously obtained value for the fractional urinary fluoride excretion (FUFE) over a 24-hour period in adults and to assess whether there are significant differences between FUFE measured during the diurnal (7 a.m. and 6 p.m.) and the subsequent nocturnal (6 p.m. until 7 a.m. of the following day) periods.


METHODS
Urine was collected over 24 h from 60 healthy female volunteers residing in Santiago, Chile. The individuals' fluoride intakes over the diurnal and nocturnal periods were calculated from their corresponding F ingestion, measured by dietary analysis. Separate urine collections during both periods were obtained from each volunteer. The fluoride concentrations were measured with a fluoride-ion-selective electrode either directly (urine, water and beverages) or after sample treatment with the microdiffusion technique (food).


RESULTS
The average 24-hour FUFE value was 0.69, with a 95% CI of 0.65-0.72, while the average FUFE for the diurnal period was 0.46 (95% CI: 0.42-0.50), and the corresponding result for the nocturnal period showed a significantly higher (paired t test, p < 0.0001) amount of 1.09 (95% CI: 0.97-1.22).


CONCLUSIONS
A recently published result for the daily FUFE value (0.71) in adults was confirmed. The diurnal average FUFE value is significantly lower than the average nocturnal one. Accepting that approximately 10% of the fluoride intake is not absorbed, the daily fluoride retention can be preliminarily estimated as 20% of the ingested fluoride.
Institute of Nutrition and Food Technology, INTA, University of Chile, Santiago, Chile. avilla@inta.cl
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Villa
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Anabalón
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Cabezas
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Rugg-Gunn
D000328:Adult; D001628:Beverages; D002327:Cariostatic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D005457:Fluoridation; D005459:Fluorides / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000652:urine*; D006801:Humans; D008657:Metabolic Clearance Rate; D012016:Reference Values; D018709:Statistics, Nonparametric
D002327:Cariostatic Agents; D005459:Fluorides