New research reaffirms recommended fluoride levels do not negatively affect IQ

ADA endorses community water fluoridation as safe way to prevent caries

New research reaffirms that fluoride at levels recommended for community water fluoridation in the U.S. does not negatively impact IQ or cognitive function.

A cohort study published April 13 in the Proceedings of the National Academy of Sciences found no evidence that community water fluoridation is negatively associated with adolescent IQ or adult cognitive functioning. It is the first study in the U.S. to track childhood exposure to community water fluoridation and its potential cognitive effects in adolescence through age 80.

“Municipal Water Fluoridation, Adolescent IQ, and Cognition Across the Life Course: Evidence From the Wisconsin Longitudinal Study” includes data from a representative sample of 10,317 participants from Wisconsin. The authors inferred participants’ fluoride exposure from historical records on community water fluoridation, their adolescent IQs from state testing records, and their cognition later in life from assessments given at ages 53, 64, 72 and 80 as part of the Wisconsin Longitudinal Study.

Participants exposed to community water fluoridation did not perform significantly worse or better than their peers who were never exposed, regardless of the age at which their cognition was assessed.

These U.S.-based findings are consistent with similarly strong cohort studies from Australia and New Zealand that also found fluoridated water had no effect on IQ scores in children or cognitive neurodevelopment. The level of fluoride in water in those two countries is comparable to that in the U.S.

The American Dental Association endorses community water fluoridation as a safe, beneficial, cost-effective and socially equitable public health measure for preventing dental caries in children and adults.

“As a dentist concerned about public health, it’s reassuring to see rigorous, patient-focused research,” said ADA President Richard Rosato, D.M.D. “The evidence is clear — community water fluoridation is not linked to lower IQ or reduced cognitive outcomes. As policymakers consider the value and safety of adding fluoride to reach optimal levels, they can rest assured that the latest systemic reviews of fluoride in this country did not find negative associations between fluoride and IQ.”

A narrative review published online April 6 by The Journal of the American Dental Association also found no association between fluoride exposure from community water fluoridation and children’s IQ scores. The review provided an overview of the literature available on this topic, including the NTP Monograph.

The monograph, a systematic review from the National Toxicology Program, was cited by a U.S. judge in his 2024 decision directing the Environmental Protection Agency to take regulatory action to address the alleged risk posed by community water fluoridation. However, the report did not provide any new or conclusive evidence necessitating changes in current community water fluoridation practices, and its unorthodox research methods and flawed analyses were criticized by the ADA and other science-based organizations.

The JADA review again highlighted issues with the application of the NTP Monograph’s findings to the U.S. Although there may be an association between lower IQ and fluoride exposure in countries with naturally occurring fluoride levels much higher than the recommended level for community water fluoridation in the U.S., these studies included methodological weaknesses and failed to establish causation between fluoride and cognition. The review stated there is no established biological mechanism to explain fluoride’s effect on IQ.

“An Update on Community Water Fluoridation, Part 2: Fluoride Exposure and Children’s IQ Scores — Relevance of Systematic Reviews and Meta-Analyses to Community Water Fluoridation” will appear in the May issue of JADA.

It follows the publication of another article by the same authors in the April issue of JADA that evaluated the benefits and cost-effectiveness of community water fluoridation and the impact of its discontinuation.

In “An Update on Community Water Fluoridation, Part 1: Mechanism of Action, Effectiveness, and Cost Savings,” the authors reviewed observational studies published between 2014 and 2025 that were peer reviewed and conducted in the U.S. or other countries with highly developed economies. Some were part of government-commissioned reports.

The studies found community water fluoridation typically reduced caries by about 25% and its cost was a small fraction of the increased treatment costs expected in the absence of fluoridation. Stopping community water fluoridation consistently resulted in higher caries levels and greater restorative needs.

A systematic review published in the April issue of JDR Clinical & Translational Research, after first being published online in June 2025, also summarized existing evidence on the effect of community water fluoridation on caries. It included 74 studies and found communities where water was fluoridated experienced fewer caries.

“I hope this will put an end to the false narrative on fluoride because the objective, long-term studies do not demonstrate any connection to cognitive abilities in youth or elderly,” Dr. Rosato said. “The latest evidence should reassure the public that optimally fluoridated water is safe, effective and something I confidently recommend for patients of all ages.”

For more information on community water fluoridation and related ADA advocacy, visit ADA.org/fluoride.