Drinking fluoridated water is not linked to lower cognitive abilities, researchers said in a new study. Critics, meanwhile, said the study had significant limitations that undercut its conclusions.
Students who lived in areas that added fluoride to water tested better in school, John Robert Warren of the University of Minnesota and other researchers said in the paper, published Nov. 19 by Science Advances.
“We find robust evidence that young people who are exposed to typical, recommended levels of fluoride in drinking water perform better on tests of mathematics, reading, and vocabulary achievement in secondary school than their peers who were never exposed to sufficient levels of fluoride,” the researchers said.
“Based on our findings, we conclude that fluoride exposure─at recommended levels─does not negatively impact young people’s cognition. In fact, it may even have modest positive effects,” Warren, who has a doctorate in sociology, told The Epoch Times in an email.
The scores came from 58,270 high school students across 1,020 schools in the United States in 1980.
Tests of memory, fluency, and attention completed by 13,980 of the former students in 2021, when they were about 60, found no differences between people who had lived in areas with fluoridated water and those who had not.
The research was funded by the National Institutes of Health (NIH) and the Alzheimer’s Association. Conflicts of interest included one author being paid for work on cognitive assessments by several companies, such as IQVIA.
“NIH funding of a study does not imply that the agency agrees with its findings,” Andrew Nixon, communications director for the Department of Health and Human Services, the parent agency of the NIH and Centers for Disease Control and Prevention, told The Epoch Times in an email.
Limitations of the study included not knowing how much fluoride the participants actually consumed, and assuming that children spent their entire childhoods in the same place where they went to high school.
“We now have access to different data that─while representative of only a single state, not the whole country─allows us to overcome both limitations,” Warren said.
Fluoride in Water
Fluoride, a mineral, has for decades been added to water across the nation to help prevent tooth decay. Federal officials recommend 0.7 milligrams of fluoride per liter in drinking water.
Health Secretary Robert F. Kennedy Jr. said in April he would direct the CDC to stop recommending fluoridation of municipal water. The CDC still recommends water fluoridation, saying it prevents cavities and saves money for families and health care facilities.
Some states and cities, including Utah and Santa Fe, New Mexico, have recently stopped adding fluoride to water, citing recent research and uncertainty over risks and benefits, and many European countries have for years banned water fluoridation.
The new paper came after a systematic review from the National Toxicology Program, published in 2024, found evidence that exposure to fluoride levels generally higher than the amount in fluoridated water in the United States is associated with lower IQ in children.
The evidence of an association with lower levels of fluoride “appeared less consistent than results of studies at higher exposure levels,” the authors of the review stated.
A federal judge, based on that paper, ordered federal officials to strengthen rules around fluoride in drinking water. The government has appealed that ruling.
Another systematic review and meta-analysis, published in January, identified an association between exposure to water with fluoride at levels higher than 1.5 milligrams per liter.
Authors of the new paper highlighted how those levels of exposure are typically not recorded in the United States.
“Our results cast doubt on the assertion that exposure to recommended levels of fluoride reduce academic achievement or cognitive functioning,” they wrote.
Critics Weigh In
Christine Till, a professor at York University’s Faculty of Health, has been studying the impact of water fluoridation on pregnant women and children for years. In 2019, she and other researchers found that women with high levels of fluoride in urine samples were more likely to have children with lower IQ scores.
Till, who has a doctorate in psychology, reviewed the new paper and said that while it adds some new information, its limitations, such as not measuring how much fluoridated water the participants actually drank, weaken its conclusions.
“Overall, the results of one study do not counter the extensive literature showing links between early-life fluoride exposure and lower IQ in children,” she told The Epoch Times in an email.
Chris Neurath, science director for the Fluoride Action Network, an organization that sued the government over water fluoridation, told The Epoch Times via email that the study was highly flawed and does not outweigh the results of other recent research.
David Savitz, a professor emeritus of epidemiology at the Brown University School of Public Health, said in a commentary, also published by Science Advances, that the paper had shortcomings, including a lack of neurobehavioral testing, but that it had several strong features, such as its national scale.
He noted that the results aligned with another paper from Swedish researchers that was published in 2021.
“Until clear evidence exists that water fluoridation lacks public health benefit or compelling evidence of harm at the level of fluoride exposure in fluoridated water, neither of which has occurred, it seems foolhardy to interfere with a long-established and well-recognized public health success,” Savitz wrote.
He disclosed that he was an expert witness for the government in the legal case brought over fluoride, which is on appeal.
Correction: A previous version of this article misstated at which university Christine Till is a professor. The Epoch Times regrets the error.