New evidence from University of Minnesota study counters the claim that fluoride lowers IQ
Minneapolis, MN - November 19, 2025
Fluoride is a naturally occurring mineral and is often added by municipalities to drinking water as a public health measure to strengthen teeth and reduce the risk of cavities.The U.S. Centers of Disease Control (CDC) cites fluoridation of drinking water as one of the top ten public health interventions of the 20th century, but misinformation has led some to worry that it harms children’s IQ. A new study published in Science Advances from the University of Minnesota finds just the opposite: Fluoride is associated with better—not worse—cognitive performance in adolescence.
The study used data from the nationally representative High School and Beyond cohort study, which has followed a sample of 25,000 people from high school through midlife. It is the very first U.S.-based study to consider effects of fluoride within levels that occur naturally and that are recommended by the CDC. The study found:
- Children exposed to recommended levels of fluoride in drinking water through late adolescence do better than other children on vocabulary, reading, and mathematics achievement tests in 12th grade
- This advantage persists, though is no longer statistically significant, through approximately age 60
“This is a great example of understanding the data and scientific research used to draw conclusions,” says Gina Rumore, one of the study's authors at the Life Course Center. “While extremely high levels of fluoride like we see in some parts of the world can be toxic, fluoride in drinking water at recommended levels is not. Fluoridating drinking water is known to have massive oral health benefits, and now it appears that it also leads to better—not worse—cognitive test performance.”
While highly publicized misinformation claims fluoride has negative effects on children’s IQ, prior research on the topic was done using smaller and non-representative samples of people in China, India, and Iran where children are exposed to levels of fluoride that are many times greater than what we ever see in the United States. While this research doesn’t answer the question of why exposure to recommended levels of fluoride is associated with improved cognition, it does fill a gap in existing research.
According to study author John Robert Warren, “It is vitally important for the public—and people who influence public policy—to know that there is absolutely no credible scientific evidence to support the claim that putting fluoride in municipal drinking water at recommended levels harms children’s IQ. In fact, the opposite appears to be true.”
This study was made possible through support from the National Institutes on Aging.