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 US Centers of Disease Control (CDC) cites fluoridation of drinking water as one of the top 10 public health interventions of the 20th century.
However, 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.
New evidence from researchers at the university is prompting fresh debate over the long-standing controversy about fluoride and brain health. Their study finds that exposure to fluoride at levels typical of U.S. community drinking water — about 0.7 milligrams per liter — is not linked to lower intelligence, and may be associated with modestly better cognitive outcomes in adolescence.
Fluoride has been added to public water supplies in the United States for decades as a proven tool to prevent tooth decay.
Fears that ingesting fluoride could harm brain development, particularly children’s IQ, were reignited by a 2024 report from the National Toxicology Program (NTP), part of the US Department of Health and Human Services, which concluded that higher levels of fluoride exposure were associated with lower IQ scores in children.
However, that NTP finding was largely based on studies conducted outside the United States, often in areas where fluoride levels are far above the levels normally found in US water systems — and where socio-economic and environmental factors can differ significantly.
“It was very important to look at the effects of fluoride exposure within the range experienced by typical American children,” said John Robert Warren, a Sociology Professor at the University of Minnesota and Director of the Institute for Social Research and Data Innovation, one of the study’s lead authors. “Our results cast doubt on the assertion that exposure to recommended levels of fluoride reduces academic achievement or cognitive functioning.”
The Minnesota team analyzed data from the nationally representative High School and Beyond cohort — a dataset following more than 26,000 individuals from adolescence into later life — and linked fluoride exposure from birth through high school with performance on reading, mathematics and vocabulary tests. Instead of finding reduced scores, the research detected a slight cognitive advantage in teens who grew up in fluoridated communities compared with those who did not.
Importantly, the study authors emphasized that their research is observational, meaning it does not prove causation.
Socioeconomic status, nutrition, education quality and other variables influence cognitive outcomes and must be considered when interpreting results. Still, the findings are significant because they rely on representative US data and fluoride exposures at levels actually encountered in most American water supplies.
Public health experts note that, while debates over fluoride’s safety often focus on isolated studies or meta-analyses, the broader scientific community generally supports fluoridation at recommended levels.
The American Dental Association and other professional groups continue to endorse water fluoridation, citing strong evidence of its benefits for dental health and no convincing evidence of harm to cognitive function at typical exposure levels.
Critics of fluoridation are likely to point to past meta-analyses suggesting an inverse relationship between fluoride exposure and children’s IQ, particularly in settings where concentrations are much higher than those in U.S. systems. However, because most of that research involved non-American populations and higher doses of fluoride, public health researchers argue that such findings are not directly applicable to decisions about community water fluoridation policies in the United States.
As policy debates continue, the University of Minnesota study adds a crucial piece of evidence suggesting that fluoride at current US drinking water levels does not lower IQ and may even correlate with modest cognitive benefits — a finding that could influence future guidelines and regulatory discussions around public water fluoridation.
The study was made possible through support from the National Institutes on Aging.
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Dr. Joseph D. Lim, Ed. D., is the former Associate Dean of the College of Dentistry, University of the East; former Dean, College of Dentistry, National University; Past President and Honorary Fellow of the Asian Oral Implant Academy; Honorary Fellow of the Japan College of Oral Implantologists; Honorary Life Member of the Thai Association of Dental Implantology; and Founding Chairman of the Philippine College of Oral Implantologists. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI, graduated Doctor of Dental Medicine, University of the Philippines, College of Dentistry, Manila, 2011; Bachelor of Science in Marketing Management, De la Salle University, Manila, 2002; and Master of Science (MSc.) in Oral Implantology, Goethe University, Frankfurt, Germany, 2019. He is an Associate Professor; Fellow, International Congress of Oral Implantologists; and Fellow, Philippine College of Oral Implantologists. For questions on dental health, e-mail limdentalcenter@gmail.com./PN
