University of Minnesota Study Challenges Fluoride IQ Claims

Research from the University of Minnesota has found a positive relationship between fluoridated water and cognitive performance, contradicting claims made by a report from the National Toxicology Program (NTP). The NTP’s August 2024 report suggested that “higher levels of fluoride exposure” were linked to lower IQ in children, raising concerns about the safety of fluoride in drinking water.

Fluoride, a mineral commonly added to public water supplies to combat tooth decay, is also present in many dental products. According to John Robert Warren, a sociology professor at the University of Minnesota and director of the Institute for Social Research and Data Innovation, the NTP study was “provocative” yet “troubling.” He pointed out that none of the 74 studies reviewed by the NTP were conducted in the United States and that they relied on non-representative convenience samples.

Warren highlighted a critical flaw in the NTP’s findings: they were based on fluoride levels of 1.5 milligrams per liter or more, significantly higher than the typical concentration of 0.7 milligrams per liter found in municipal water systems. He stated, “Nobody’s talking about implementing water fluoridation in communities with that extraordinarily high of a dosage,” questioning the relevance of the NTP report to public policy discussions regarding fluoride use.

In response, Warren and his colleagues investigated whether water fluoridation at the lower concentration of 0.7 mg/L impacts cognitive function. They recognized that there had been no long-term studies examining the effects of fluoride on cognitive health. “If fluoride lowers children’s IQs, then we should also see that it would lower long-term cognitive health,” Warren noted.

The team analyzed data from the High School & Beyond study, a nationally representative survey that began in 1980, tracking participants into adulthood. Their analysis categorized participants based on fluoride exposure: no exposure, some exposure, and exposure throughout childhood. The results indicated no negative relationship between fluoride exposure and cognitive performance. In fact, the study found a positive association, although the cognitive advantage observed was not statistically significant.

These findings, published on November 19, 2024, in Science Advances, may provide valuable insights for city leaders considering the implications of fluoride in drinking water. Following the NTP report, Utah implemented a ban on adding fluoride to drinking water supplies, driven by concerns over potential risks to children’s IQ.

Warren emphasized the importance of accurate information, stating, “If you think that fluoride lowers kids’ IQs, well now there’s a serious risk. But if the risk has been overstated — if there’s no threat to children’s IQ, then I think the decision becomes a little bit easier.”

According to the Centers for Disease Control and Prevention, approximately three-quarters of Americans who receive tap water from community systems have access to fluoridated water. As of 2020, Minnesota ranked as the third-most-fluoridated state, with 98.8% of its community water systems utilizing fluoride.

This new research could shift the conversation around community water fluoridation, providing evidence for policymakers to consider in light of public health.