The case for removing fluoride from drinking water supplies has weakened. Research to date shows no link between water fluoridation and decreased cognition in children or adults.
Researchers examined the education and medical records of a large, nationally representative group of Americans. They found no evidence that water fluoridation was associated with lower test scores in high school or lower cognition scores later in life. The researchers say the findings appear to undermine one of the most common arguments against adding fluoride to people’s drinking water.
“If fluoride lowers your IQ, we should see lower test scores in places where they fluoridate the water. And we absolutely did not,” lead author John Warren, a sociologist and demographer at the University of Minnesota’s Minnesota Population Center, told Gizmodo.
fluoride bogeyman
In some groups, water fluoridation has long been blamed for a number of health problems.
For example, longtime anti-science cynic Robert F. Kennedy Jr. has argued that fluoride is causing massive IQ loss and increasing bone cancer. And since taking over as U.S. Secretary of Health and Human Services under the second Trump administration, Kennedy has said he will ask the CDC to no longer recommend water fluoridation nationally.
Many of the biggest claims made about fluoride are unproven by current data, including the alleged cancer risk. That said, there has been more intense scientific debate over whether water fluoridation can affect children’s IQ. For example, a review published earlier this January and conducted by scientists at the National Institutes of Health found a possible link between lower IQ levels and greater fluoride exposure in children.
Study researcher John Warren says, as others have said, that this review focused primarily on studies that looked at much higher and potentially toxic levels of fluoride exposure than is typically seen in the US. And in general, there has been only limited research examining this possible link among American children.
“It really shocked me that there was a problem with that meta-analysis,” Warren said.
loss reduction
Warren and his colleagues believed they had access to data that could provide a clearer picture of the relationship between fluoride and cognition: the High School and Beyond study. The project, started in the 1980s, collected reading, mathematics, and vocabulary test scores from more than 26,000 high school students across the country; A subgroup of surviving participants were also contacted as adults and asked to undergo medical evaluation, including testing of their cognition, until the age of 60.
Many people grew up in the towns and neighborhoods where they attended high school, especially in the 1980s. So the researchers cross-referenced other federal data on water fluoridation levels in areas where children went to school. This data was used as a proxy for fluoride exposure as people grew up. Although many parts of the US began routinely fluoridating their water in the early 1980s, many did not or had not adopted their local standards, allowing researchers to compare different levels of fluoride exposure between neighborhoods.
Overall, Warren’s team failed to find a negative relationship between relatively high levels of fluoride in the city’s drinking water and high school children’s test scores; If anything, the average score for children exposed to fluoridated water in the US is actually slightly higher. This modest benefit faded by age 60, but researchers still found no link between reduced cognition in adults and exposure to fluoridated water in childhood. They also found that some neighborhoods exceed recommended fluoride levels.
“If [fluoride] Lowers your IQ, which is considered a permanent change, so you would expect to have less cognition at age 60. But that’s not what we found,” Warren said.
The team’s findings were published Wednesday in Science Advances.
future of fluoridation
Warren says this study only looked at the association between cognition and fluoride, so it alone can’t tell us whether water fluoridation is a net positive. But he points out that other research has confirmed its benefits for improving dental health.
Researchers also know that children’s test scores are an imperfect indicator of IQ. But now they’re conducting a similar study of children in Wisconsin, where they have access to IQ test scores.
Anyway, these findings clearly weaken the justification for removing fluoride from people’s drinking water. And while the researchers plan to study the topic further, they argue that to properly justify such an exclusion based on hypothetical concerns about IQ would require much stronger evidence than is currently collected.
“What we’re showing is that this IQ story—doesn’t hold up in a representative sample in the United States at fluoride levels that are actually relevant to the policy discussion,” Warren said.
Unfortunately, there is a shortage of reasons these days. In addition to RFK Jr.’s federal campaign, Florida and Utah have already passed legislation to ban water fluoridation this year, and still more states and cities may soon follow suit.
Fluoride probably isn’t lowering anyone’s IQ. But its fear has definitely crept in the minds of some people.