Fluoride is a naturally occurring mineral that has been shown to strengthen teeth and reduce cavities. Many municipalities add fluoride to their drinking water - called community water fluoridation - as a public health measure to support dental health. In recent years, however, some have claimed that ingesting fluoride can harm children's IQ.
Researchers at the University of Minnesota led a team that investigated the connection between fluoride in drinking water and children's IQ to see if these claims had merit. The study, published in PNAS, examined Wisconsin state testing records, archival information about when Wisconsin cities began to fluoridate their water, and data from the Wisconsin Longitudinal Study, which has followed a random sample of 10,317 high school seniors from 1957 through 2026. Key findings include:
- There is no evidence supporting a connection between community water fluoridation and children's IQ.
- There is also no evidence supporting a connection between community water fluoridation and cognitive functioning at various points later in life.
- Findings confirm evidence published in previous research which also used a national sample, but considered school achievement test scores instead of actual IQ scores.
"Utah, Florida and many municipalities have chosen to remove fluoride from drinking water based on flawed studies that considered the IQ effects of exposure to massive doses of fluoride," said lead researcher John Robert Warren, a professor in the College of Liberal Arts. "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."
Future research will continue examining the benefits and harms of adding fluoride to community drinking water.
Study co-author Gina Rumore, co-director of the Demography and Economics of Aging Coordinating Center at the University of Minnesota, noted that these findings "provide no support for the claim that community water fluoridation has any harmful effect on children's IQ or on adult cognition."
The research was supported by the National Institute on Aging, the Vilas Estate Trust, the National Science Foundation and the Spencer Foundation.
About the College of Liberal Arts
For more than 150 years, the College of Liberal Arts has played a central and enduring role in shaping lives, for the good of Minnesota and the world. CLA is the largest college in the University of Minnesota system with nearly 500 world-class faculty instructing more than 12,000 undergraduate and 1,400 graduate students. CLA is home to 31 academic departments and more than 20 interdisciplinary research centers in the arts, social sciences and humanities. Learn more at cla.umn.edu.
