Fractional Urinary Fluoride Excretion of Young Female Adults during the Diurnal and Nocturnal Periods

Abstract

Objectives: 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.

Relationships between Fluoride Intake, Urinary Fluoride Excretion and Fluoride Retention in Children and Adults: An Analysis of Available Data

“…This quantitative finding is lower than the previously generally mentioned approximate value of 0.5 [Ekstrand, 1996;Whitford, 1996] and might become relevant when speculations are made on the accumulation of fluoride in human hard tissues. On the other hand, this finding is in line with recently reported FFR values for adults living in 'optimally' fluoridated areas [Villa et al, 2008].…”

“…The materials and methods used in these Chilean unpublished studies were the same as those reported in detail in previous papers [Villa et al, 2000[Villa et al, , 2004[Villa et al, , 2008. In brief, individual assessments were made of TDFI, including beverages, food and swallowed fluoride toothpaste together with the corresponding DUFE data.…”

“…Measuring fluoride intake is possible but requires good co-operation from subjects, skilled staff to record intake and is usually expensive. If it were possible to obtain valid predictions of fluoride intake from measurements of urinary fluoride excretion, the risk of dental and skeletal fluorosis might be assessed more easily, since collecting urine for fluoride measurement is relatively simple [Marthaler, 1999;Villa et al, 2000Villa et al, , 2008Franco et al, 2005]. In addition, assessing fluoride exposure at the time of risk to the developing dentition and skeleton is obviously preferable to waiting several years for fluorosis to become clinically evident.…”

“…While the first reports of simultaneous measurement of TDFI and daily urinary fluoride excretion (DUFE) were published many years ago, several studies have been undertaken recently (partly due to the need to learn of the relative importance of the many sources of ingested fluoride and the increasing risk of dental fluorosis) in children [Ekstrand et al, 1984[Ekstrand et al, , 1994Villa et al, 2000;Zohouri and Rugg-Gunn, 2000;Haftenberger et al, 2001;Franco et al, 2005;Zohouri et al, 2006;Maguire et al, 2007] and adults [Maheshwari et al, 1981;Spencer et al, 1970Spencer et al, , 1975Villa et al, 2004Villa et al, , 2008. It was thought desirable to bring this information together so as to examine more closely the relationship between TDFI, DUFE and daily fluoride retention (DFR) in order to assist understanding of these physiological variables.…”

Scientific Opinion on Dietary Reference Values for fluoride

“…There was, however, large within-and between-subject variation in plasma concentrations (C max and AUC) (Maguire et al, 2005;Villa et al, 2008;Whitford et al, 2008).…”