Research finds no link between fluoride in tap water and lower adolescent IQ

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University of Minnesota researchers analyzed the IQ test results of over 10,000 men and women over time, starting when they were 16 years old and continuing through adulthood. Those who lived in communities that added fluoride to their tap water “did not perform significantly worse (or better) than their peers who were never exposed,” the study concluded. This remained true when participants tested again at ages 53, 64, 72 and 80.

The analysis refutes a meta-analysis published last year, which found an inverse relationship between fluoride exposure and children’s IQ scores. The University of Minnesota research team sharply criticized that conclusion in its own study, emphasizing that none of the articles included in the 2025 meta-analysis used data from the United States. Other nations, the scientists noted, have much higher dosages of fluoride in their drinking water.

“Because levels of fluoride added to municipal drinking water in the U.S. are so much lower, almost all prior evidence from those international studies is not relevant to U.S. public policy debates,” lead author John Robert Warren said in a statement.

Though the meta-analysis was denounced by other public health experts, including the American Dental Association, it has gained traction with skeptics and conspiracy theorists. Health and Human Services Secretary Robert Kennedy Jr. has repeatedly sowed misinformation about fluoride and vowed to remove it from all American water systems. The Republican-led governments of Utah and Florida banned the naturally occurring mineral from their tap water in 2025.

The latest study drew on data from the Wisconsin Longitudinal Study, which has tracked a random sample of 10,317 people who graduated from state high schools in 1957 over their lives. The researchers used Census data and other federal resources to match water wells to each participant’s county and determine when fluoride was introduced.

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