What fluoride supplements really do — and why the FDA’s cracking down

A long-standing dental treatment aimed at preventing cavities in children may soon disappear from the US market, as the Food and Drug Administration (FDA) moves to eliminate fluoride supplements over safety concerns.

The agency announced on May 13 that it intends to remove prescription fluoride tablets and drops, citing potential links to altered gut bacteria, thyroid disorders, and lowered IQ. The decision does not affect fluoride in toothpaste, gels, or mouthwashes.

“The best way to prevent cavities in children is by avoiding excessive sugar intake and good dental hygiene, not by altering a child’s microbiome,” said FDA Commissioner Martin Makary, who is directing the agency to reassess the risks of these supplements.

The announcement has drawn swift criticism from dental professionals and scientists, who argue that the FDA’s concerns are based on weak and irrelevant studies.

They warn that the move could deepen existing oral health disparities, particularly in rural areas where fluoridated water is unavailable.

“It is a complete mystery to me why they think that this is an appropriate way to make the American public healthier,” said Scott Tomar, a dentist and epidemiologist at the University of Illinois Chicago. “The decision is based on some of the flimsiest evidence I’ve seen.”

Tomar noted that fluoride supplements have been prescribed for decades with proven success in reducing tooth decay.

He also questioned the relevance of studies cited by the FDA, many of which involve communities in rural China exposed to extremely high fluoride levels from coal burning and contaminated water—conditions not present in the United States.

The American Dental Association also pushed back, saying the cited research does not support banning fluoride at levels currently prescribed.

“A review of the studies offered does not in fact demonstrate any harmful effects,” the association said in a statement.

Even scientists involved in the FDA’s cited studies were surprised by the decision.

“There is no convincing evidence to support a stance that fluoride use in childhood has a detrimental effect on microbiome development,” said microbiologist Gary Moran of Trinity College Dublin.

Meanwhile, states such as Florida and Utah have moved to ban the addition of fluoride to public water systems, further narrowing access.

Health experts warn that eliminating fluoride supplements would remove a critical line of defense for children in unfluoridated regions.

Fluoride supplements, available as drops or tablets, have long been prescribed to children living in areas where water supplies lack fluoridation. The aim is to prevent cavities by mimicking the protective benefits of fluoridated drinking water, said Scott Tomar

"The dosage ranges from 0.25 to 1 milligram, depending on the child's age," Tomar explained. "It’s comparable to what children would ingest naturally if they drank water containing 0.7 milligrams per litre of fluoride."

Caroline Orr, a microbiologist at Teesside University, described fluoride’s benefits as “proven,” pointing to its role in remineralising tooth enamel, reversing early decay, and disrupting harmful bacteria. “It strengthens the teeth and reduces cavities,” she said.

Despite these long-standing advantages, the FDA has signalled plans to remove ingestible fluoride supplements for children, citing concerns about their impact on gut microbiota, IQ, thyroid function, and even weight gain.

Tomar was critical of the evidence being used to justify the decision. “Most of the literature the FDA cited is low-quality and high-risk for bias,” he said.

“The strong studies from countries like Denmark, Australia, Spain and Sweden show no link to IQ or neurodevelopment issues.”

“The thyroid accusation has no substantial scientific support,” said Tomar. “As for weight gain, that's a new and unsupported claim.”

“The science just isn’t there,” he added. “These claims are not new, and they’ve consistently failed under scrutiny.