The truth about fluoride
Fluoride is found in dental products such as toothpaste and helps protect teeth from cavities and fights off bacteria in the mouth. It is also added to public water supplies.
Unbranded – Lifestyle
People who drink fluoridated local water for long periods of time are just as smart as those who don’t, the first study of its kind has found.
The study, published Monday, April 13 in the Proceedings of the National Academy of Sciences, is the first to examine the effects of fluoridated water on cognition into late adulthood, far beyond childhood and adolescence, the usual focus of fluoride research. This study expands on a previous study published in November 2025 and is also unique in that it is the first to analyze data representative of the U.S. population up to age 60.
As the Centers for Disease Control and Prevention notes, community water fluoridation, the act of adding minerals to a community’s water supply to enhance dental health, has historically been considered a revolutionary achievement in public health. But the practice has become a hot spot in recent years, with Health and Human Services Secretary Robert F. Kennedy Jr. saying in 2025, without evidence, that fluoride exposure would make children “stupid.” The validity of frequently cited studies, particularly those using data from outside the United States, has been questioned.
“Like everyone else, I was intrigued by the claims that there was a link between fluoride and IQ,” says study co-author Rob Warren, a professor at the University of Minnesota. “When I looked at the evidence, I wasn’t impressed. The evidence used to support that claim wasn’t great. So I started thinking, ‘Well, what can we do with existing data about the United States that is representative of the population and considers fluoride at a level that we actually care about?’
To do this, the study’s authors looked to data from the Wisconsin Longitudinal Study, which followed 10,317 people in the state from high school graduation in 1957 through their lives. The authors examined the results of standardized tests to measure intelligence and mental function in these adults up to age 80, and categorized them by the time they were first thought to have been regularly exposed to fluoridated water (from birth to age 8 or age 14) based on historical community records.
To make these measurements, the researchers reviewed IQ tests administered to school participants at age 16 and similar standardized cognitive tests administered at ages 53, 64, 72, and 80.
Similar to the previous analysis on which it was based, this study found no evidence that community water fluoridation was associated with later IQ or cognitive decline in adolescents.
“(With that information) we can answer the question, ‘Is it true that children exposed to fluoride have lower IQs?’ And the answer is no, not at all,” Warren said. “And because the same people have been followed, they’re now in their 80s…We could also ask, ‘Is there a difference in their cognitive abilities at any point in their lives?’ And the answer was no.”
Although this study improves on previous research by applying a finer-toothed comb to address confounding factors and tracking participants’ lifelong geographic movements, it has its own limitations. The biggest limitation is that fluoride exposure was estimated based only on local water records, rather than each individual’s complete unique profile.
Fluoride and how it is used in the United States
Fluoride, which occurs naturally in water, soil, plants, rocks, and even the air, was discovered by the late 1930s as a tool to help prevent cavities and cavities. In 1945, Grand Rapids, Michigan became the first city to fluoridate its local water, adjusting the existing levels in the supply to a therapeutic 1.0 parts per million (ppm).
Fluoride levels have since been adjusted to 0.7 ppm or 0.7 milligrams per liter of water, which is considered optimal for preventing cavities. The maximum amount allowed by the Environmental Protection Agency for drinking water in the United States is 4.0 milligrams per liter.
The most recent CDC data available from 2022 reports that 72.3% of the U.S. population using community water sources received fluoridated water, a percentage that is fairly consistent with 2020’s 72.7%. Although the CDC maintains that fluoridated water is safe and cost-effective, questions about the potential dangers posed by water fluoridation have existed for as long as the practice has been widespread.
According to the Cleveland Clinic, the potential for fluoride toxicity does exist, but a person would have to ingest enough fluoridated water to die from water intoxication before the amount becomes harmful or fatal.
“On a very personal level, you shouldn’t have to worry that your child will be harmed by drinking fluoridated tap water, or at least harmed in neurocognitive development,” Warren said of current U.S. standards. “On a personal level, there are much, much more important things to worry about than that.”
Growing anti-fluoride push
President Kennedy led a new charge against fluoridated water, saying in November 2024 that the second Trump administration would “advise all water systems in the United States to remove fluoride from public water supplies” citing unfounded health concerns.
At a Cabinet meeting with President Donald Trump in April 2025, Kennedy praised Utah for becoming the first state to ban local governments from adding fluoride to public water supplies and said he was working on “changing federal fluoride regulations to change the recommendations.” He similarly argued, “The more[fluoride]you ingest, the stupider you become. This country needs smart children, it needs healthy children.”
At this and other conferences, President Kennedy and like-minded anti-fluoride advocates cited small studies that showed mixed results regarding the potential link between fluoride exposure and IQ. They have been criticized by organizations such as the American Dental Association and the National Academies of Sciences, Engineering, and Medicine for using data from other countries outside the United States, studying fluoridation levels much higher than those allowed in the United States, employing inadequate statistical rigor, and having other methodological flaws.
“Most[of these studies]compare children who were exposed to incredibly high levels of fluoride in small villages in China, Iran, and India to children who were only exposed to ‘some’ high levels of fluoride. They are not at all representative of people outside the village,” Warren explained. “The policy question[in the US]is not whether it’s toxic or supertoxic levels. That’s not what anyone here is talking about. It’s recommended levels or nothing. And most of the research doesn’t really make sense because it’s about high doses.”
President Kennedy and his administration backtracked somewhat on their anti-fluoride messaging in 2026, with Acting CDC Director Dr. Jay Bhattacharyya telling a House subcommittee in March that fluoride is “essential for oral health,” before adding that too much can have “neurological and developmental effects.”
Several states, including Utah, Florida, North Dakota, Tennessee, and Montana, have passed or are considering legislation to ban or limit the addition of fluoride to local water sources.
