Fluoride plays a central role in public health, and new research has expanded the conversation. This article examines what the most extensive U.S. study on fluoride adds to the evidence.
By Ayesha Khan, MD, MBA
In contemporary dental practice, fluoride remains a cornerstone of preventive oral health. Decades of evidence demonstrate that fluoride significantly reduces dental caries—the most common chronic childhood disease—through mechanisms that enhance enamel remineralization and inhibit bacterial metabolism. However, in recent years, scientific inquiry has expanded beyond enamel and caries prevention to examine potential systemic effects — notably on neurodevelopment and cognition.
Fluoride’s Public Health Legacy and Scope of Exposure
Since the mid-20th century, water fluoridation at approximately 0.7 mg fluoride per liter has been widely practiced in the United States as a preventive public health intervention, and the CDC credits it as one of the 20th century’s major public health achievements. The primary intent of fluoridation is to reduce tooth decay across populations, especially among children and underserved communities. Contemporary exposure arises not only through drinking water but also through toothpaste, mouth rinses, professional applications, and naturally occurring sources.
Scientific investigations seek to delineate how exposure levels, timing, and context may influence neurodevelopment and cognition outcomes over time.
The Largest U.S. Study to Date
In late 2025, researchers published what to date is the most comprehensive U.S. epidemiological investigation into fluoride exposure and cognitive outcomes. The “Childhood fluoride exposure and cognition across the life course” study examined data from the nationally representative High School and Beyond cohort, comprising 26,820 students from more than 1,000 high schools across the United States. Investigators assessed fluoride exposure from conception through adolescence and linked it with standardized cognitive performance measures in secondary school and later-life assessments around age 60.
Contrary to concerns that fluoride might impede neurodevelopment, the study found that exposure to fluoride at levels typical in U.S. community water fluoridation was associated with modestly better cognitive performance in adolescence, including reading, mathematics, and vocabulary outcomes. By late adulthood (~60 years), cognitive differences converged and were statistically indistinguishable, suggesting no long-term detrimental effects attributable to typical fluoride exposure. The authors concluded that within the range of recommended fluoride concentrations, water fluoridation is not associated with reduced IQ or adverse cognitive outcomes.
Previous research from the University of Queensland, evaluating adolescents and young adults (aged 16–26) who participated in the Australian National Child Oral Health Study, also found no significant negative association between early-life water fluoridation exposure and full-scale IQ measured using standardized WAIS-IV testing. In fact, exposed individuals exhibited an average difference of +1.07 IQ points, though the differences were not statistically significant.
These studies highlight that within the bounds of contemporary fluoridation practice, there is no compelling evidence of detrimental cognitive effects—a conclusion that dental and public health professionals often cite when advocating for community fluoridation.
Mechanistic Considerations and Lifespan Exposure
Experimental animal studies provide mechanistic insight, particularly at high doses. For instance, prolonged exposure to elevated fluoride levels has been associated with morphological and functional changes in the hippocampus—a brain region critical for learning and memory—suggesting potential neurotoxicity at supraphysiologic concentrations.
The latest peer-reviewed monograph and meta-analysis, published in JAMA Pediatrics and as part of the NTP State of the Science Monograph, concluded that higher fluoride exposure—particularly in communities where drinking-water fluoride levels exceed 1.5 mg/L—was moderately associated with lower IQ scores in children. This association was most evident above the WHO guideline of 1.5 mg/L and was not explicitly linked to community water fluoridation at 0.7 mg/L.
Clinical Evidence and Considerations for Practice
Dental professionals recognize that fluoride’s effects are dose-dependent: controlled exposure supports enamel health, while excessive intake beyond public health standards can lead to dental fluorosis with implications beyond aesthetics.
In light of emerging neurodevelopmental research and evolving exposure patterns, the following points should guide clinical discourse and public health recommendations:
- Assess total fluoride exposure at intake (water source, dental products, diet), with special attention to infants and young children.
- Individualize fluoride recommendations based on caries risk, age, and existing environmental or dietary exposure.
- Reinforce proper toothpaste dosing, i.e., smear for children under 3, pea-sized for ages 3–6, with supervised brushing to limit ingestion.
- Counsel expectant parents using balanced, evidence-based guidance; avoid unnecessary supplemental fluoride unless indicated.
- Recommend water testing for patients on private wells or in areas with naturally elevated fluoride levels.
- Stay current on emerging research and distinguish high-exposure studies from standard community fluoridation levels.
In Conclusion
In summary, dental health professionals can confidently interpret current evidence as supportive of fluoride’s safety at recommended exposure levels, with no robust evidence of a linkage to adverse cognitive outcomes over time. Continued research, especially high-quality longitudinal and mechanistic studies, will further clarify dose thresholds and developmental windows of susceptibility. Meanwhile, fluoride’s role in reducing dental caries remains a foundational component of preventive oral care, aligning optimal public health outcomes with individual patient guidance grounded in scientific evidence.
References:
- https://www.cdc.gov/mmwr/preview/mmwrhtml/00056796.htm
- Warren, J. R., Rumore, G., Kim, S., Grodsky, E., Muller, C., Manly, J. J., & Brickman, A. M. (2025). Childhood fluoride exposure and cognition across the life course. Science Advances, 11(47), eadz0757.
- Bittencourt, L. O., Dionizio, A., Ferreira, M. K. M., Aragão, W. A. B., de Carvalho Cartágenes, S., Puty, B., ... & Lima, R. R. (2023). Prolonged exposure to high fluoride levels during adolescence to adulthood elicits molecular, morphological, and functional impairments in the hippocampus. Scientific Reports, 13(1), 11083.
- National Toxicology Program. (2024). NTP monograph on the state of the science concerning fluoride exposure and neurodevelopment and cognition: a systematic review. Ntp Monograph, (8), NTP-MGRAPH.
Author: Ayesha Khan, MD, MBA, is a registered physician, former research fellow, and enthusiastic blogger. With a wide range of articles published in renowned newspapers and scientific journals, she covers topics such as nutrition, wellness, supplements, medical research, and alternative medicine. Currently serving as the Vice President of Social Communications and Strategy at Renaissance, Ayesha brings her expertise and strategic mindset to drive impactful initiatives.
