University of Minnesota Study Challenges Fluoride IQ Claims

A recent study from the University of Minnesota has found a positive correlation between fluoridated water supplies and cognitive function, directly opposing claims made by the National Toxicology Program (NTP). The NTP’s August 2024 report suggested that “higher levels of fluoride exposure” were linked to reduced IQ in children.

Fluoride is commonly added to municipal water supplies to prevent tooth decay. 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 raised important issues. He pointed out that none of the 74 studies reviewed by the NTP were conducted in the United States, and none used representative samples, relying instead on convenience samples from various communities.

Warren highlighted a critical flaw in the NTP report: it based its findings on fluoride levels of 1.5 milligrams per liter, significantly higher than the typical municipal level of 0.7 mg/L. “Nobody’s talking about implementing water fluoridation in communities with that extraordinarily high of a dosage,” he remarked. This discrepancy, he argued, rendered the NTP’s conclusions largely irrelevant to discussions on community water fluoridation.

In response to the NTP findings, Warren and his colleagues sought to investigate whether water fluoridation at the standard level of 0.7 mg/L impacts cognitive function. He noted a lack of research on the long-term effects of fluoride exposure, stating, “If fluoride lowers children’s IQs, then we should also see that it would lower long-term cognitive health.”

To examine this, the research team utilized data from the High School & Beyond study, a nationally representative survey of high school students initiated in 1980, which has tracked participants into adulthood. They analyzed the 12th-grade test scores of students categorized by fluoride exposure: those with no exposure, some exposure, and consistent exposure throughout childhood.

The findings revealed no negative relationship between fluoride exposure and cognitive performance. In fact, Warren noted, “the association was positive,” suggesting a potential cognitive advantage for those exposed to fluoridated water. Although this advantage persisted into adulthood, it was not statistically significant.

These results also considered various factors that could influence cognitive ability and test scores, such as socioeconomic status and geographic location. The study, published on November 19, 2024, in the journal Science Advances, aims to inform city leaders as they evaluate the pros and cons of fluoridation in their water systems.

Following the NTP report, for instance, Utah decided to halt the addition of fluoride to its drinking water supplies. Warren emphasized the implications of these decisions, 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 (CDC), approximately three-quarters of Americans who receive tap water from community systems are supplied with fluoridated water. Minnesota ranks as the third-most-fluoridated state, with 98.8% of its community water systems utilizing fluoride as of 2020.

This latest research contributes to the ongoing debate surrounding fluoride use in public health and highlights the need for further investigation into its long-term effects on cognitive health.