Exposure to Fluoride in Tap Water Show No Cognitive Harm in Major Study

A major study finds no link between exposure to fluoride and lower cognition, contradicting claims made by HHS Secretary Robert F. Kennedy, Jr. Rather, the investigation found a positive correlation between exposure to recommended levels of fluoride and better standardized test scores.

“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,” the authors of the study wrote.¹

Does Fluoride Exposure Affect Cognition?

Emerging research circulated and supported by the HHS and Secretary Kennedy claims that fluoride exposure is linked to lower cognition in children. As a result, 2 states have since fully banned fluoridation of water, with others anticipated to follow.²

Addition of fluoride in public water systems began in 1945 in an effort to prevent tooth decay, one of the most common chronic childhood diseases at the time. The success of this endeavor was praised by the CDC, who claimed it was one of the greatest public health achievements of the 20th century.^2,3

However, the emerging research associating fluoride exposure and lower IQ undermines these efforts. Although higher levels of exposure could be associated with lower cognition, the levels present in United States water systems fall well below of those levels. Currently, the recommended level of fluoride in drinking water in the United States is 0.7 mg/liter, which was lowered from 0.7 to 1.2 mg/liter in 2015.¹

In the study, co-author John Robert Warren, a sociologist from the University of Minnesota, cites a study published by Taylor et al, which did find a positive association between poorer cognition and fluoride exposure at levels higher than 1.5 mg/liter. When calculating for levels below that, their findings were null.¹

There is little research on associations between lower levels of fluoride and poor cognition, leading Warren and his colleagues to investigate areas with fluoride levels within the typical, recommended range.

“Whereas most prior research has estimated effects of exposure to extremely high levels of fluoride, we consider exposure to levels of fluoride within the range typical in most places and of greatest relevance to policy debates about government water fluoridation,” they said.¹

Warren and colleagues examined data from Americans enrolled in the National Center for Education Statistics’ High School and Beyond cohort, which followed students from 1980 through 2021. The original 1980 sample included 26,820 participants, of whom roughly half completed the 2021 follow-up.¹

The team estimated each individual’s fluoride exposure from conception through the end of high school. They then compared those exposure levels with participants’ standardized reading, math, and vocabulary scores during high school, as well as with memory assessments conducted when the participants were in their 60s.¹

What Does Long-Term Data Show About Fluoride’s Impact on Cognitive Outcomes?

Their findings showed that exposure to safe, recommended levels of fluoride was associated with better test performance, offering no evidence of harm to cognitive function. These results help fill a critical gap in understanding fluoride’s effects on cognition and neurodevelopment, providing a more realistic picture than prior studies that focused on exposure levels far higher than those encountered in everyday life.¹

“Our results provide strong evidence that exposure to fluoride—at levels ordinarily seen in the United States and of relevance to policy debates about municipal water fluoridation—has benefits for adolescent cognition and is, at worst, not harmful for later-life cognitive functioning,” the authors concluded.¹

Although the authors did not determine why exposure to normal fluoride levels in tap water improved test scores, Warren hypothesizes that it may have to do with children attending school more consistently as better oral health is associated with decreased illness.

Taken together, the findings counter recent assertions that standard fluoridation poses a cognitive risk and instead reinforce decades of evidence supporting its safety. By examining real-world exposure levels across four decades, the researchers provide one of the most comprehensive assessments to date that underscores the continued public health value of water fluoridation in the United States.

“Until clear evidence exists that water fluoridation lacks public health benefit or compelling evidence of harm at the level of fluoride exposure in fluoridated water, neither of which has occurred,” the lead author wrote, “it seems foolhardy to interfere with a long-established and well-recognized public health success.”¹

REFERENCES

1. Warren J, Rumore G, Kim S, et al. Childhood fluoride exposure and cognition across the life course. Science Advances. November 19, 2025. doi: 10.1126/sciadv.adz0757

2. Ruble J. Is fluoride friend or foe? Pharmacy Times. June 25, 2025. Accessed November 24, 2025. https://www.pharmacytimes.com/view/is-fluoride-friend-or-foe-

3. Basilio H. Fluoride in tap water not linked to lower child IQ, massive study finds. Scientific American. November 19, 2025. Accessed November 24, 2025. https://www.scientificamerican.com/article/massive-study-debunks-one-of-rfk-jrs-biggest-claims-about-fluoride-in-tap/