New study finds fluoride linked to cognitive performance

Dental Tribune International

Tue. 2 December 2025

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MINNEAPOLIS, US: Since the election of Donald Trump as US president in 2024, the question of water fluoridation in the country has become increasingly politicised. This is largely because Secretary of Health and Human Services Robert F. Kennedy Jr has consistently contradicted the scientific community by linking the measure to a range of health problems, including reduced IQ. As a timely investigation into this fraught issue, a major nationally representative US study has examined whether typical levels of fluoride exposure in childhood—those found in municipal water systems operating within public health guidelines—are associated with cognitive outcomes in adolescence and later adulthood. The research provides important evidence for ongoing debates about water fluoridation policy.

The relationship between water fluoridation and intelligence levels has been researched thoroughly, yet some of the prior research has been limited by study design, including lack of representative samples and failure to account for confounding factors. The current study investigates how fluoride exposure at levels commonly found across the US relates to cognitive performance at two key life stages: adolescence and around 60 years of age. Unlike previous research, which often focused on populations exposed to extremely high fluoride concentrations, this analysis evaluates exposures within the recommended range of around 0.7 mg/l. It uses the High School and Beyond cohort, a large longitudinal dataset tracking more than 58,000 students sampled in 1980 and followed through adulthood.

The researchers combined detailed records of municipal fluoridation practices with measurements of naturally occurring groundwater fluoride to classify participants according to whether they had sufficient fluoride exposure throughout childhood or during part of their childhood or not at all. Cognitive outcomes were based on reading, mathematics and vocabulary assessments in the final year of secondary school and on a global measure of cognitive function at around 60 years of age.

After accounting for socio-economic, demographic and geographic factors, the study found consistently positive associations between recommended fluoride exposure and adolescent cognitive performance. The estimated benefits were modest, but were consistent across all cognitive measures. In the research article, the authors state: “We find robust evidence that young people who are exposed to typical, recommended levels of fluoride in drinking water perform better on tests of mathematics, reading and vocabulary achievement in secondary school than their peers who were never exposed to sufficient levels of fluoride.”

In adulthood, cognitive outcomes were also positively associated with recommended fluoride exposure in adolescence, though the effects were smaller and not statistically significant. Supplementary analyses designed to rule out policy-driven community differences suggested that the observed associations were unlikely to be explained by broader social or economic factors.

While the authors note limitations—including incomplete residential histories and the inability to measure actual fluoride consumption—the findings challenge claims that typical fluoridation levels harm cognitive development. Instead, the results indicate that recommended fluoride exposure may support adolescent academic performance and appears not to impair later-life cognitive functioning.

The article, titled “Childhood fluoride exposure and cognition across the life course”, was published online on 21 November 2025 in Science Advances.