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Fluoride is present in various sources, including soil, groundwater, plants, and many foods, and the mineral is commonly added to some toothpastes and other dental products due to its oral health benefits at low levels.¹ In many countries, the fluoride concentrations in drinking water are regulated.¹ In the US, reports suggest that drinking water fluoridated at the recommended levels (?0.6 mg/L and <2.0 mg/L) reduces cavities by an estimated 25% in children and adults.² However, prolonged high-level exposure to fluoride has been linked to negative health effects such as dental and skeletal fluorosis,³ and studies continue to explore the biological impacts of cumulative or high-level fluoride exposures, including mitochondrial dysfunction,^4,5 neurotoxicity,^4,6 iodine metabolism,⁷ and thyroid health.^8-10

Observational studies conducted outside of the US have also examined the health impacts of fluoride intake among different populations and life stages, including children and their prenatal or postnatal fluoride exposures. Some studies suggest that higher exposure levels may be linked to poorer neurobehavioral development.^11-12 Recently, a US-based study investigated these associations and found similar results.¹³

New Study: Prenatal Fluoride Exposure & Childhood Neurobehavior

The 2024 Malin et al prospective cohort study is reportedly the first US-based study to examine associations between prenatal fluoride exposure and child neurobehavioral outcomes.¹³ Specifically, this investigation assessed links between third trimester maternal urinary fluoride levels and child neurobehavior at three years of age. The study used urine samples and neurobehavioral data from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) pregnancy cohort. The MADRES cohort included primarily Hispanic women with low socioeconomic status who resided within the city of Los Angeles, California. Maternal urine samples were collected and archived between 2017 and 2020, while the children’s neurobehavioral data was assessed between 2020 and 2023. In all, 229 mother-child pairs completed the three-year assessment and were included in the study.¹³

Investigators used specific gravity-adjusted maternal urinary fluoride (MUF_SG) as the biomarker for prenatal fluoride exposure and used the Preschool Child Behavior Checklist (CBCL) to quantify neurobehavior, with possible scores between 28 to 100. Of note, scores from 60 to 63 were identified as borderline clinical and scores greater than 63 were clinical.¹³ The following results were reported:¹³

• The median MUF_SG at the mothers’ third trimester was 0.76 (0.51-1.19) mg/L.
• Of the 116 female children and 113 male children included in the mother-child pairs, at three years of age, 32 (14%) had a CBCL Total Problems score in the borderline clinical or clinical range.
• A 1-IQR (interquartile range) was defined as 0.68 mg/L. Per results, a 1-IQR increase in MUF_SG was associated with nearly double the odds of a borderline clinical or clinical CBCL Total Problems score (OR 1.83) as well as with a 2.29-point increase of the CBCL Internalizing Problems score.

Overall, the investigators concluded that in this cohort study, a 0.68 mg/L (i.e., 1 IQR) increase in MUF_SG during pregnancy was associated with a significantly increased odds of borderline clinical and clinical CBCL scores at three years of age. The study results suggest that increased prenatal fluoride exposure while living in optimally fluoridated areas of the US may increase the risk of childhood neurobehavioral problems.¹³

Conclusion

Studies have suggested some health benefits from regulated fluoride exposure as well as potential health risks. As research continues to elucidate how fluoride exposures impact health, the functional medicine model recognizes the clinical importance of understanding the chronic or acute environmental components that are part of an individual patient’s complete health story. A patient’s historical and current physical environment in addition to cumulative environmental exposures may impact health outcomes, and implementing practical steps as well as lifestyle-based approaches that address these exposures may be part of a personalized treatment strategy.

References

1. National Institutes of Health Office of Dietary Supplements. Fluoride: fact sheet for health professionals. National Institutes of Health. Updated June 17, 2024. Accessed June 24, 2024. https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/
2. Boehmer TJ, Lesaja S, Espinoza L, Ladva CN. Community water fluoridation levels to promote effectiveness and safety in oral health – United States, 2016-2021. MMWR Morb Mortal Wkly Rep. 2023;72(22):593-596. doi:15585/mmwr.mm7222a1
3. World Health Organization Chemical Safety and Health Unit. Inadequate or excess fluoride. World Health Organization. Accessed June 13, 2024. https://www.who.int/teams/environment-climate-change-and-health/chemical-safety-and-health/health-impacts/chemicals/inadequate-or-excess-fluoride
4. Wang D, Cao L, Pan S, et al. Sirt3-mediated mitochondrial dysfunction is involved in fluoride-induced cognitive deficits. Food Chem Toxicol. 2021;158:112665. doi:1016/j.fct.2021.112665
5. Kumar S, Shenoy S, Swamy RS, Ravichandiran V, Kumar N. Fluoride-induced mitochondrial dysfunction and approaches for its intervention. Biol Trace Elem Res. 2024;202(3):835-849. doi:1007/s12011-023-03720-1
6. Guth S, Hüser S, Roth A, et al. Toxicity of fluoride: critical evaluation of evidence for human developmental neurotoxicity in epidemiological studies, animal experiments and in vitro analyses. Arch Toxicol. 2020;94(5):1375-1415. doi:1007/s00204-020-02725-2
7. Somporn R, Lapinee C, Umponstira C, Weterings R, Chaiwong S. Iodine status in pregnant women having urinary fluoride in contaminated areas: a case study of Phayao Province. J Environ Public Health. 2023;2023:3677359. doi:1155/2023/3677359
8. Iamandii I, De Pasquale L, Giannone ME, et al. Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis. Environ Res. 2024;242:117759. doi:1016/j.envres.2023.117759
9. Ferreira MKM, Nascimento PC, Bittencourt LO, et al. Is there any association between fluoride exposure and thyroid function modulation? A systematic review. PLoS One. 2024;19(4):e0301911. doi:1371/journal.pone.0301911
10.  Hall M, Lanphear B, Chevrier J, et al. Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort. Sci Total Environ. 2023;869:161149. doi:1016/j.scitotenv.2022.161149
11.  Green R, Lanphear B, Hornung R, et al. Association between maternal fluoride exposure during pregnancy and IQ scores in offspring in Canada. JAMA Pediatr. 2019;173(10):940-948. doi:1001/jamapediatrics.2019.1729
12.  Farmus L, Till C, Green R, et al. Critical windows of fluoride neurotoxicity in Canadian children [published correction appears in Environ Res. 2022;215(Pt. 3):114468 doi:10.1016/j.envres.2022.114468]. Environ Res. 2021;200:111315. doi:1016/j.envres.2021.111315
13.  Malin AJ, Eckel SP, Hu H, et al. Maternal urinary fluoride and child neurobehavior at age 36 months. JAMA Netw Open. 2024;7(5):e2411987. doi:1001/jamanetworkopen.2024.11987