Fluoride Action Network


Dietary factors are known to influence urinary fluoride (UF) levels in nonpregnant people. Maternal UF is used as a biomarker of fluoride exposure; however, dietary influences on UF during pregnancy are unknown. We compared UF levels and assessed the associations between UF and five select dietary influences in pregnancy vs. one-year postpartum: dietary fluoride (F), calcium intake from diet (Ca-diet), calcium intake from supplements (Ca-sup), dietary acid load (AL), and table salt use (TS) in 421 women exposed to fluoridated salt in the Mexican diet. Spot UF (mg/L) was measured by microdiffusion/fluoride-specific electrode and dilution-corrected with specific gravity (SG). Dietary variables were estimated from a validated Food Frequency Questionnaire. Comparisons among UF in pregnancy vs. one-year postpartum were performed with non-parametric tests. Associations between dietary variables and UF were assessed using random effect models (for pregnancy) and linear regression (for one-year postpartum). SG-corrected UF (median, range) during pregnancy (0.77, 0.01–4.73 mg/L) did not significantly differ from one-year postpartum (0.75, 0.15–2.62 mg/L) but did increase every 10 gestational weeks, B = 0.05 (CI: 0.00–0.10). Different dietary influences on UF were identified at each state. Although Ca-diet and AL were not associated with UF in either state, Ca-sup decreased UF only during pregnancy, B = – 0.012 mg/L (CI: – 0.023–0.00). Reporting TS use was associated with 12% increase in UF only at one-year postpartum (p = 0.026). These results suggest different dietary influences on UF in the pregnant state, which need consideration when using UF as a biomarker of fluoride exposure.

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*Original abstract online at https://link.springer.com/article/10.1007%2Fs12011-021-02799-8


Data Availability

The data that support the findings of this study are available upon reasonable request.


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The authors acknowledge the American British Cowdray (ABC) Hospital in Mexico City, Mexico, for providing research facilities for the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project. We also acknowledge the active participation of women from the ELEMENT Cohort 3 and the members of the research team involved in the ELEMENT project.


This work was supported by NIEHS under grant RO1ES021446 and NIEHS/EPA grant P01ES022844/RD8354360; the Instituto Nacional de Salud Pública de México (INSP); Indiana University’s President’s International Research Award (PIRA 23–140-39), and the PhD in Dental Sciences Program, Indiana University School of Dentistry.

Author information



Gina A. Castiblanco-Rubio participated in the conception and design of the study, conduction of data analyses, statistical modeling, interpretation of results, and writing of the manuscript. Teresa V. Muñoz-Rocha participated in the management of the ELEMENT database, supervision of data analyses, supervision of statistical modeling, interpretation of data, and edition of the manuscript. Alejandra Cantoral, E. Angeles Martinez-Mier, and Martha M. Téllez-Rojo participated in the conception and design of the study, interpretation of results, and edition of the manuscript. Howard Hu was a co-founder of the ELEMENT cohort and PI of R01ES021446, and Karen Peterson is PI of NIEHS/EPA P01ES022844/RD8354360; both provided oversight of original dietary data collection and participated in interpretation of data and edition of the manuscript. Martha M. Téllez-Rojo and Adriana Mercado-Garcia supervised and coordinated field data collection. Adriana Mercado-Garcia and Adrienne Ettinger participated in the design and implementation of the original cohort study and participated in interpretation of data and edition of the manuscript.

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Correspondence to Gina A. Castiblanco-Rubio.

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This study was conducted according to the guidelines laid down in the Declaration of Helsinki and the ethics committee of the INSP, Indiana University, Harvard University, and the University of Michigan approved all procedures involving research study participants.

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Written informed consent was obtained from all study participants.

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The authors declare no competing interests.

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*Original abstract online at https://link.springer.com/article/10.1007%2Fs12011-021-02799-8