Filling a glass of water from the sink just isn’t the no-brainer it used to be. As if the prospect of “forever chemicals” isn’t anxiety-inducing enough—the recent news about some states removing fluoride from their drinking water over fears the chemical could harm children’s brain development brought controversy to a public health practice that had been trusted for decades.
But this week, a sweeping new study that tracked people for more than six decades offers some reassurance. A team of sociology, aging, and health experts has found that fluoridated water systems are not to blame for intellectual or developmental issues.
Publishing their findings the Proceedings of the National Academy of Sciences , the team—from the University of Minnesota, University of Wisconsin, and the University of Michigan—followed over 10,000 Wisconsin residents from the time they graduated high school in 1957 all the way into their 80s. The researchers compared data from people who grew up drinking fluoridated water versus those who didn’t, and measured their brain health at multiple points across their lives.
They found drinking fluoridated water was not linked to lower IQ in adolescence or worse cognitive functioning in adulthood—not at ages 53, 64, 72, nor even at 80.
The timing of this research is especially meaningful. Several states, including Utah and Florida, have recently moved to end community water fluoridation programs, citing a 2025 analysis that suggested fluoride exposure was linked to lower IQ in children. However, the authors of this new study point out critical flaws in that earlier research: most of it examined fluoride levels far higher than what Americans are exposed to through their tap water —and, none of it used data from the United States.
The current study accounts for both those misses. Also, unlike previous research, it also tracked where participants actually lived during childhood, giving researchers a more accurate picture of how long each person was really exposed to fluoridated water.
The study’s researchers are careful to note that the study has limitations—they couldn’t directly measure how much fluoride individuals actually consumed—but the evidence produced from this rigorous analysis is consistent and clear across six decades of follow-up.
The bottom line is this for everyday Americans: based on the best available long-term U.S. data, drinking fluoridated water as a child does not appear to harm brain development or increase your risk of cognitive decline as you age.
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