Breaking: New Study Linking Fluoride to Lower IQ in Children Sparks Renewed Calls to End Water Fluoridation

A meta-analysis examining the link between children’s IQ and fluoride exposure found that the more fluoride pregnant women and young children are exposed to, the greater the decrease in a child’s IQ.

by Brenda Baletti, Ph.D.

A meta-analysis of 74 epidemiological studies examining the link between children’s IQ and fluoride exposure found that the more fluoride pregnant women and young children are exposed to, the greater the decrease in a child’s IQ.

The study, published today in JAMA Pediatrics, was conducted by scientists from the National Institutes of Health’s (NIH) National Toxicology Program (NTP).

The in-depth statistical meta-analysis is the largest and most rigorous ever conducted on fluoride, according to a commentary accompanying the study, and their findings highlight the need to “reassess systemic fluoride exposure, again.”

The researchers analyzed existing studies globally, assessed their quality and accounted for variables including age, sex, fluoride levels, types of cognitive tests used, methods for measuring fluoride exposure and study locations.

They found a significant inverse relationship between fluoride exposure and children’s IQ scores, which means as the amount of fluoride a pregnant woman or young child was exposed to increased, IQs decreased.

They also found that across high-quality studies, the effect was significant at both higher and lower fluoride levels.

The data were divided into subgroups with fluoride levels of less than 4 milligrams/liter (mg/L), less than 2 mg/L and less than 1.5 mg/L in drinking water and in urinary fluoride — which estimates a person’s total fluoride exposure.

For every 1 mg/L increase in urinary fluoride, the study found a 1.63-point decrease in IQ in children.

The results were more uncertain at lower levels because exposure contrasts were harder to identify, the researchers said.

The U.S. Public Health Service recommends communities add fluoride to their water to reduce the risk of cavities at levels of 0.7 mg/L — a number it lowered from a recommended 0.7-1.2 mg/L in 2015.

In the U.S., about 40-70% of a person’s fluoride intake comes from fluoridated drinking water.

However, fluoride levels in water alone likely underestimate a person’s total fluoride exposure, the study said. Total exposure varies by individual behavior, including how much water, coffee or tea a person drinks, processed food consumption, whether infants drink formula rather than breastmilk, or what kind of fluoridated products like toothpaste or mouthwash someone uses.

The JAMA meta-analysis is part of an investigation the NTP scientists began in 2015 into the link between fluoride exposure and lower IQ in children. The scientists published a monograph in August and today’s meta-analysis, both providing extensive data on fluoride’s neurotoxic effects on the developing brain.

NTP’s publications followed years of opposition by fluoride lobbying groups, including the American Dental Association (ADA) and public health officials, who tried to block its publication and pressure the authors to weaken and delay their findings.

The research underwent an unprecedented amount of peer review relative to all other research done by the NTP, which the former head of the NTP told The Defender was politically driven.

The results of the study “may inform future comprehensive public health risk-benefit assessments of fluoride,” the authors concluded.

The firestorm over water fluoridation

JAMA Pediatrics published the meta-analysis amid a firestorm over water fluoridation.

Public health officials and the dental lobby have for decades insisted that water fluoridation is an unquestionable public good — one of the 10 great public health achievements of the 20th century. Officials have often dismissed as conspiracy theorists citizens and even top scientists who question the practice.

However, scientific understanding of fluoride evolved over the years to reveal fluoride’s toxic effects — including on children’s cognitive development — that were unknown or ignored when public health agencies began recommending communities add it to their water supplies nearly 70 years ago.

Current recommendations for safe water fluoridation consider only the risks of dental fluorosis, a tooth discoloration caused by overexposure to fluoride in childhood that affects about 23% of the U.S. population. No recommendations or restrictions exist on water fluoridation based on its potential neurocognitive effects.

Yet in 2024 alone, in addition to the NTP’s monograph concluding that higher levels of fluoride exposure in drinking water are consistently linked to lower IQ in children, a study published in JAMA Network Open in May found that children born to women exposed during pregnancy to fluoridated drinking water in Los Angeles were more likely to have neurobehavioral problems.

In September 2024, a federal judge ruled that the scientific evidence, including the NTP’s research, shows that water fluoridation at current U.S. levels poses an “unreasonable risk” of reduced IQ in children and ordered the Environmental Protection Agency (EPA) to take regulatory action.

The ruling concluded a historic lawsuit, which dragged on for over seven years, against the agency. The suit was brought by environmental and consumer advocacy organizations and individual parents and children seeking to end fluoridation.

Less than two weeks after the September 2024 ruling, Cochrane published an updated review concluding that adding fluoride to drinking water provides minimal, if any, dental benefits, especially compared with 50 years ago.

Since then, many cities and towns across the U.S. have decided to end water fluoridation. Florida’s surgeon general advised governments to stop fluoridating their water, citing the neuropsychiatric risks — particularly for pregnant women and children.

Robert F. Kennedy Jr., president-elect Donald Trump’s nominee to lead the U.S. Department of Health and Human Services (HHS) said on social media that Trump would push to end water fluoridation on his first day in office.

Kennedy’s comments triggered a wave of articles in the mainstream press defending the practice, albeit with some commenters conceding that conventional wisdom on fluoride needs to be revisited.

HHS houses the Centers for Disease Control and Prevention (CDC), which makes recommendations about water fluoridation levels.

Two commentaries: the experts debate

Dr. Steven M. Levy, professor at the University of Iowa and member of the ADA’s National Fluoridation Advisory Committee, wrote a scathing response to today’s JAMA study, accusing the authors of selectively including research and doing analyses in a way that “raised substantial concerns about the validity and usefulness of the article.”

Levy criticized the authors for not discussing critiques made by reviewers or the changes made to earlier conclusions. Many of those critiques were driven in part by Levy and the ADA committee he serves on, through public and behind-the-scenes pressure revealed in documents plaintiffs obtained via Freedom of Information Act (FOIA) requests during the trial.

Levy cited a meta-analysis by Dr. Jayanth V. Kumar et al. nine times in his four-page response, using it as key evidence to discount the NTP’s findings. That analysis found no association between fluoride and lowered IQ at low fluoridation levels.

Kumar and Levy are colleagues on the ADA advisory committee. The study was co-authored with Dr. Susan Fisher-Owens, who receives funding from Colgate. The study intentionally omitted data that would counter the authors’ conclusions and intentionally sought to undermine the NTP’s report, according to emails obtained through public records requests.

“This commentary was an ADA hit job,” Michael Connett, the plaintiffs’ attorney in the fluoride trial, told The Defender. “I strongly suspect that Kumar was a ghost writer — one of the main authors — and Levy was the signatory, and that should have been disclosed.”

Connett’s FOIA requests uncovered the ADA’s lobbying influence.

By omitting Kumar’s name but citing his meta-analysis multiple times, Connett said, it appears that Levy is citing an independent expert. However, Levy and Kumar have been working together for years to try to undermine the NTP’s work, as court documents showed.

Levy concluded that despite “some evidence” of a “possible association” between IQ and high fluoride levels in water, current public health recommendations about fluoride, “should not be affected by the study findings.”

Dr. Bruce Lanphear, professor of Health Sciences at Simon Fraser University in Burnaby, Canada; Pamela Den Beston, DDS, Ph.D., professor of Orofacial Sciences at University of California San Francisco; and Christine Till, Ph.D., professor of clinical psychology at York University in Toronto, disagreed with Levy’s commentary.

The three, who have conducted major studies on fluoride’s toxicity, said the JAMA meta-analysis showed the need to reassess current fluoride recommendations.

Since water fluoridation began in the U.S. tooth decay has plummeted, they wrote. However, the same trend has occurred in countries that don’t fluoridate their water, possibly due to the use of fluoride toothpaste or strategies to reduce sugar intake — a strategy the U.S. has not pursued.

Research has since shown that fluoride’s ability to prevent cavities is based on topical application, not mineralization during tooth formation as previously thought.

The CDC and ADA regularly cite data showing fluoridated water reduced cavities by 25%. However, the authors said that data is based on low-quality studies mostly conducted before fluoridated toothpaste became widely available. They pointed to the updated Cochrane review, which found little to no benefit from water fluoridation.

In their own research, Lanphear et al. found levels of urinary fluoride higher than 1.5 mg/L among pregnant women in Canada who drank fluoridated water.

Advocates for water fluoridation argue the practice is necessary to protect low-income children who may not have regular access to dental care. However, they wrote, those children are at higher risk for exposure to other neurotoxicants like lead as well, therefore water fluoridation may pose an even greater risk to them.

Given that NTP’s analysis showed fluoride’s negative effects may be associated with cognitive function, they concluded, “It is time for health organizations and regulatory bodies to reassess the risks and benefits of fluoride, particularly for pregnant women and infants.”

The EPA has until the end of the month to file an appeal contesting the federal judge’s order that the agency make new rules regulating water fluoridation based on the risk it poses to children’s neurodevelopment.

“NTPs findings highlight the need for the EPA to move quickly in taking regulatory action to protect the public from the risk posed by fluoridation,” Connett said.