Indiana University-Purdue University Indianapolis (IUPUI) / The use of maternal urinary fluoride as a biomarker of prenatal fluoride exposure in epidemiology studies is increasing. However, the knowledge on maternal exposure to fluoride and its biomarkers, has not increased alongside. The objective of this dissertation was to improve our understanding of the dietary intake of fluoride (a major source of fluoride exposure), and spot urinary fluoride levels during pregnancy. Two secondary data analyses utilizing data from the Early Life Exposures in Mexico to ENvironmental Toxicants (ELEMENT) project were conducted, in a population of women living in a salt-fluoridated community. The first study estimated the dietary intake of fluoride over the course of pregnancy and assessed the influence of compliance with the dietary recommendations of intake of beneficial nutrients for pregnancy (calcium, iron, folate and protein) on the dietary intake of fluoride. The second study compared spot urinary fluoride in women during pregnancy and non-pregnancy (using one-year postpartum as a proxy for the non-pregnant state) and assessed associations between dietary factors (dietary fluoride intake, addition of table salt, calcium intake from diet and supplements, and dietary acid load) and urinary fluoride levels at each state. Results revealed that the median dietary intake of fluoride in pregnant women was 0.7 mg/day, increased with gestational age and in women who were moderately and highly compliant with recommendations of intake of beneficial nutrients for pregnancy. On the other hand, spot urinary fluoride levels during pregnancy did not significantly differ with those of women one-year postpartum, increased with gestational age, and decreased in calcium-supplemented women only during pregnancy. The dietary intake of fluoride, calcium, and dietary acid load were not associated with urinary fluoride in either state. Finally, reporting the addition of table salt to meals was associated with an increase in urinary fluoride only at one-year postpartum. The studies in this dissertation highlight the need for a deeper understanding of fluoride exposure and its biomarkers in the pregnant population. / 2022-07-01

Background: Studies of assessing dietary fluoride intake in children have employed different dietary methods mainly “2-day duplicate” and “3-day food diary” methods. However, none of these methods have been validated or standardised. Main aims: The main aims of the current study were to develop a better understanding of strengths and weaknesses of dietary assessment methods “2-day duplicate plate” and “3-day food diary” by comparing dietary fluoride intake estimated by each method and evaluate the validity of the two methods for estimating dietary fluoride intake in young children. Methods: Sixty one healthy 4-6 year old children living in fluoridated area of the north-east of England since birth were recruited via 10 primary schools. Dietary information was collected using “2-day duplicate plate” and “3-day food diary” methods. Two 24-h urine samples and two samples of post brushing expectorate (a mixture of saliva, toothpaste and water used to rinse after brushing) from each child. Completeness of 24-h urine samples was checked using urinary excretion of creatinine and urinary flow rate. Validity of the two dietary assessment methods was checked by measuring urinary excretion of nitrogen and potassium as independent validity checks. Total daily fluoride intake from diet and toothpaste ingestion and urinary fluoride excretion was determined for each child. Results: All participated children completed all aspects of the study. According to the validity criteria, dietary data of 58 (95%) children, when collected by the 3-day food diary, were considered valid. However, when the dietary data were collected by the 2-day duplicate plate method, the data for 46 (75%) children were viewed as valid. Mean total dietary fluoride intake was 0.533 mg/d by the 3-day food diary method and 0.583 mg/d by the 2-day duplicate plate method. No statistically significant difference in total dietary fluoride intake was observed between the two methods. The mean difference in estimated dietary fluoride intake by the two dietary assessment methods was -0.050 mg/d with 95% limits of agreement of -0.501 to + 0.401 mg/d. Conclusion: Either the 3-day food diary or the 2-day duplicate plate method can be used when investigating mean total daily dietary fluoride intake of a population. However the methods cannot be used interchangeably at the individual level.

There have only been few investigations comparing total fluoride intake and the fluoride proportion excreted in urine in pre–school children. In addition, the results of available studies are conflicting. Total fluoride intake was assessed in 11 healthy children aged 3–6 years on 2 consecutive days and urinary fluoride excretion was determined. The duplicate–diet approach was used for the assessment of fluoride intake from solid and liquid foods. Fluoride intake from toothbrushing was calculated as the difference between the amount of fluoride in the paste put on the toothbrush and the drinking water (fluoride concentration 0.25 mg/l) used for rinsing vs. the fluoride amounts recovered in the toothpaste spat out and in the rinsing water. Use of fluoridated domestic salt and/or fluoride tablets was recorded. The children’s intake of fluoride from food averaged 202.5±116.2 μg F/day. They swallowed an average amount of 273.9±175.6 μg F/day when brushing their teeth. Daily fluoride ingestion from all sources totalled 930.7±391.5 μg or 53.0±21.4 μg/kg body weight. On average 51.5% of the fluoride ingested was excreted in urine. The wide interindividual variation makes it necessary to evaluate the urinary excretion rate for fluoride in larger study populations with varied fluoride exposure. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

There have only been few investigations comparing total fluoride intake and the fluoride proportion excreted in urine in pre–school children. In addition, the results of available studies are conflicting. Total fluoride intake was assessed in 11 healthy children aged 3–6 years on 2 consecutive days and urinary fluoride excretion was determined. The duplicate–diet approach was used for the assessment of fluoride intake from solid and liquid foods. Fluoride intake from toothbrushing was calculated as the difference between the amount of fluoride in the paste put on the toothbrush and the drinking water (fluoride concentration 0.25 mg/l) used for rinsing vs. the fluoride amounts recovered in the toothpaste spat out and in the rinsing water. Use of fluoridated domestic salt and/or fluoride tablets was recorded. The children’s intake of fluoride from food averaged 202.5±116.2 μg F/day. They swallowed an average amount of 273.9±175.6 μg F/day when brushing their teeth. Daily fluoride ingestion from all sources totalled 930.7±391.5 μg or 53.0±21.4 μg/kg body weight. On average 51.5% of the fluoride ingested was excreted in urine. The wide interindividual variation makes it necessary to evaluate the urinary excretion rate for fluoride in larger study populations with varied fluoride exposure. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.