Studies on the Dietary Intake of Fluoride and the Concentration of Fluoride in Urine Over the Course of Pregnancy

Abstract

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.