A new study has found that people exposed to the recommended levels of fluoride in drinking water do not experience negative cognitive impacts, which contrasts the studies citied by the Trump administration on the subject.
Health Secretary Robert F. Kennedy Jr has long been an advocate for removing fluoride from drinking water, citing studies that found a correlation between fluoride in drinking water and a reduction in child IQ.
Some states – such as Florida and Utah – have already taken measures to ban the addition of fluoride to public drinking water systems, however, this latest study suggests that fluoride may not have a negative impact on cognitive health, and possibly the opposite effect.
Newsweek has contacted HHS via email for comment.
Why It Matters
Fluoride has been added to drinking water for decades, on the basis it helps strengthen tooth enamel, making it more resistant to acid attacks from plaque, bacteria and sugars.
However, the practice recently became more controversial when research unveiled the health risks associated with higher levels of exposure to fluoride, and a growing movement of people began to say the addition of the substance to their water was an infringement on their rights.
Some scientists have since responded to these concerns, noting that it is not the substance, but the dose, that should be of concern – a dose which can be regulated and controlled to remain at safe levels.
File photo: a public water tap (left) and U.S. Secretary of Health and Human Services (HHS) Robert F. Kennedy, Jr (right). | Paul Sancya/AP (left) and Aaron Schwartz/Sipa via AP (right)
What To Know
The study, published the journal Science Advances on November 19, found that fluoride exposure, specifically at recommended levels, does not negatively impact young people’s cognition, and instead could have modest positive effects.
Lead author of the study and professor of sociology at the University of Minnesota, John Robert (Rob) Warren, told Newsweek that it was actually the National Toxicology Program’s 2025 report that “motivated” him and his team to investigate the science some more.
He said that they wanted to understand the impacts of fluoride on child cognitive health, specifically at the recommended levels, as he said nearly all of the studies considered in the 2025 JAMA Pediatrics study included in the report “modeled the IQ consequences of exposure to fluoride levels much higher than those found in public drinking water in the U.S.”
“Even the ‘low exposure’ comparison groups in the studies they reviewed typically experienced fluoride levels considerably higher than those found almost anywhere in the U.S.,” he added.
He also said that none of the studies considered by the 2025 JAMA Pediatrics study were conducted on children in the U.S., instead mostly examining “extremely poor, rural people in China (45 of the 74 studies), India (9), Mexico (4), or Iran (4).”
Therefore, in conducting their study, Warren said he and his team were “motivated to use nationally representative data on American adolescents and to assess the impact on children’s cognition of being exposed to recommended levels of fluoride,” which he said was “the evidence needed to make policy decisions.”
While he said it wasn’t the scientist’s place to say whether water should be removed or added to drinking water, he said the decision should be based on “weighing the costs and benefits.”
“There is overwhelming evidence about the benefits of fluoride, at recommended levels, for dental health. The evidence for the costs has been much worse in terms of scientific quality and rigor; that’s where we come in,” he said.
What People Are Saying
Robert (Rob) Warren, professor of sociology at the University of Minnesota, told Newsweek: “This is a textbook example of why it is so important to conduct scientific research using data collected from people who represent the whole population. This is also a textbook example of why it is dangerous to base public policy decisions on evidence that is entirely irrelevant to the question at hand. The vast majority of the studies reviewed by Taylor et al (2025) investigate the effects of extremely high levels of fluoride ? exposures that are not relevant to public policy debates. Nobody is proposing to put fluoride in drinking water at concentrations several times higher than recommended levels. The question should be, ‘What are the effects of fluoride at 0.7 parts per million as opposed to no fluoride at all?’ The evidence to which we are responding ? and which has been used in so many policy arguments ? simply doesn’t answer that question. We hope our study fills that void.”
David Bellinger, a professor of neurology and psychology at Boston Children’s Hospital and Harvard Medical School, told Newsweek: “The issue of fluoride neurotoxicity at the lower levels of exposure remains controversial. These studies are difficult to conduct, and epidemiology is an imperfect science. It is the weight of the evidence that will ultimately provide the evidence base for public policy. This study adds some new information, but it cannot be considered to be definitive. It has some important strengths, having been conducted using a nationally representative cohort from the U.S. population, involving exposure to water with fluoride concentrations less than the concentrations in many of the studies that have reported fluoride neurotoxicity.”
He added: “The study also has significant limitations, particularly with regard to exposure assessment. First, no information was available about exposure at the individual level. The exposure of individuals living in the same community will vary depending on how much water they consume and so how much fluoride they are exposed to. Also, there are sources of fluoride exposure other than the community water supply. These need to be considered, but no data were available on this in the study. These factors would result in some amount of exposure misclassification.
“Toxicologists say, ‘The dose makes the poison,’ so the critical question is not whether fluoride should or should not be in drinking water, but rather, what concentration of fluoride in drinking water provides the best risk-benefit ratio. I don’t think we currently know enough to say what that optimal concentration is.”
Matthew Neidell, a professor of health policy and management at Columbia University, told Newsweek: “I’m not surprised that this study didn’t find a negative association, though I was a bit surprised to see a positive one. Many prior studies reporting negative associations between fluoride and cognition use research designs that don’t adequately control for confounding, so their findings are likely spurious. The few studies that address confounding more rigorously generally find no association. While this study doesn’t employ a quasi-experimental design, its results nonetheless contribute valuable evidence by challenging the notion of a consistent negative relationship. If estimates continue to vary between negative and positive, it highlights the need for stronger methodological approaches to help clarify the true relationship.”
Ashley Malin, a professor of epidemiology at the University of Florida, told Newsweek: “It is surprising to see that they found a potential beneficial impact of community fluoridation through conception and childhood on adolescent cognitive performance, given that most studies show an adverse association between early life fluoride exposure and neurodevelopment. It is also unclear what mechanisms would account for a beneficial effect. All of the studies conducted in North America show that prenatal fluoride exposure, even at relatively low levels, is associated with worse child cognitive development, including lower IQ, more symptoms of ADHD, and worse executive functioning. A limitation of the Warren study which the authors acknowledge is that it did not include individual measures of fluoride exposure assessment or track participants’ place of residence from conception to adolescence. Therefore, it is unknown how much of the tap water participants actually consumed and when.”
Update 11/20/25, 12:28 p.m. ET: This article has been updated with comment from Ashley Malin.
Full Interview Below
Newsweek‘s interview with John Robert (Rob) Warren, a professor of sociology at the University of Minnesota.
Q1: Were you surprised by your study’s findings, given the Trump administration’s assertions that fluoride can impact children’s IQ?
“I’m not sure ‘surprised’ is the right word. We were motivated by Taylor et al’s (2025) JAMA Pediatrics article ? which you link to above, and which came out of the National Toxicology Program’s report earlier this year ? to ask a basic question: Does exposure to fluoride at recommended levels have any impact one way or another on American children’s cognition? In other words, we were motivated to use nationally representative data on American adolescents and to assess the impact on children’s cognition of being exposed to recommended levels of fluoride – as opposed to no fluoride at all. That is the evidence needed to make policy decisions.
“This is a textbook example of why it is so important to conduct scientific research using data collected from people who represent the whole population. A virtue of our study is that we use data on a nationally representative sample of American adolescents; they are from all over America ? rich, poor, rural, urban, red states, blue states, men and women, Black, White, and Latino. The work featured in Taylor et al (2025) ? which is the basis of so many decisions by the federal government and some states ? is (a) drawn from small communities, primarily in China and India and (b) is not even representative of those communities.
“This is also a textbook example of why it is dangerous to base public policy decisions on evidence that is entirely irrelevant to the question at hand. The vast majority of the studies reviewed by Taylor et al (2025) investigate the effects of extremely high levels of fluoride ? exposures that are not relevant to public policy debates. Nobody is proposing to put fluoride in drinking water at concentrations several times higher than recommended levels. The question should be, “What are the effects of fluoride at 0.7 parts per million as opposed to no fluoride at all?” The evidence to which we are responding ? and which has been used in so many policy arguments ? simply doesn’t answer that question. We hope our study fills that void.”
Q2: How do you think fluoride impacts cognitive health based on your findings?
“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. We also find no evidence that adolescent fluoride exposure has negative long-term effects on cognitive health in midlife. If fluoride lowered children’s IQ, we would probably expect to see reduced adolescent cognition translate into lower cognition at midlife.”
Q3: Based on the findings of your study, do you think fluoride should be kept in drinking water at the levels it is currently accepted at?
“As scientists, it’s not our place to say. Policy decisions like “Should we fluoridate our municipality’s water” should be based on weighing the costs and benefits. There is overwhelming evidence about the benefits of fluoride, at recommended levels, for dental health. The evidence for the costs has been much worse in terms of scientific quality and rigor; that’s where we come in. As you write above, the administration has argued that fluoride reduces children’s IQ; we note that the evidence they use to support that claim (mainly the work cited above) is of low quality and is not applicable to the United States.
Q4: Are you concerned about the moves by some states to remove fluoride from drinking water?
It is not our place to say. But it always concerns us when major public policy decisions are based on scientific evidence that is of low quality and that is not applicable to the United States.
Original article online at: https://www.newsweek.com/new-fluoride-study-challenges-trump-admin-stance-11079581