Massive Study Debunks One of RFK Jr’s Biggest Claims about Fluoride in Tap Water

Fluoride in tap water not linked to lower IQ in children, massive study finds

By Humberto Basilio edited by Claire Cameron

A new study spanning several decades has found no evidence that exposure to recommended levels of fluoride decreases children’s cognitive abilities.

The study, published Wednesday in Scientific advances, disputes U.S. Secretary of Health and Human Services Robert F. Kennedy, Jr.’s earlier assertion that adding fluoride to tap water could harm cognition.

Citing concerns that the chemical negatively affects brain development, several U.S. cities and states are either re-evaluating the inclusion of fluoride in their water supplies or have already decided to remove it. The new paper’s findings, however, offer U.S. evidence that the public health intervention is safe, says John Robert Warren, a sociologist at the University of Minnesota and co-author of the study.

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The new study is a “much-needed addition to a large literature that shows the safety and benefits of community water fluoridation,” says Susan Fisher-Owens, a pediatrician at the University of California, San Francisco, who was not involved in the work. “This is the first study to examine this information in the United States, making it a stronger basis for making policy decisions.”

Fluoride was first added to drinking water in parts of the United States in 1945 to prevent tooth decay, one of the most common chronic childhood diseases. The practice, first adopted in Grand Rapids, Michigan, was, in 1999, hailed by the Centers for Disease Control and Prevention as one of the greatest public health achievements of the 20th century. Today, more than 62 percent of the U.S. population receives fluoridated water. Typically, U.S. water systems contain 0.7 milligrams of fluoride per liter of water.

For the new study, Warren and colleagues analyzed data from Americans included in the National Center for Education Statistics’ High School and Beyond study cohort between 1980 and 2021. The data Warren’s team analyzed began with 26,820 participants in 1980, and about half of them were part of a 2021 follow-up.

The researchers estimated each participant’s fluoride exposure from conception through 12th grade. The team then compared the participants’ exposure with their standardized test scores in reading, math, and vocabulary in high school, as well as with the memory tests they took when they reached their 60s.

The results showed that children who grew up consuming recommended levels of fluoride performed slightly better on all academic measures in high school than those who were never exposed to sufficient levels. As adults, the same people who recommended exposure showed no measurable differences in memory, attention or other cognitive abilities compared to their peers, the study found.

Although the study did not examine why people exposed to fluoridation had higher test scores in high school, Warren hypothesizes that better dental health from fluoride could have meant that these people were less likely to miss school due to illness.

“If children are healthy, they will stay in school and perform better,” agrees Fisher-Owens.

The study “is not perfect,” Warren says, because standardized test scores are not the same as an IQ test. However, his team is preparing to publish another study involving IQ tests administered to a group of people that researchers have been following since the 1950s.

The study comes amid a growing debate over water fluoridation: This year, Utah’s ban on fluoride in public drinking water took effect in May, and Florida’s did so in July.

Any policy assessment must take into account both the potential benefits and harms of fluoridation, says epidemiologist David Savitz, who was not involved in the new study. But, he adds, the evidence showing the benefits of fluoridation in the United States is stronger than that suggesting its potential harms.

“The only reason we fluoridate water is because of the benefits. If it didn’t have benefits, we wouldn’t do it,” says Savitz.

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