A new study has been published that seems to provide evidence that fluoride in our water may lower children’s IQ. Despite several flaws with the study, we know that Robert F Kennedy Jr. will use it to target fluoridation despite its benefits to dental health. Water fluoridation has been one of the greatest public health accomplishments over the past 100-plus years, tied with vaccines.

I’ve written a couple of articles about the safety and effectiveness of fluoride in our water systems, and the CDC, which will soon be under RFK Jr’s authority as Secretary of Health and Human Services, is solidly on the side of the importance of water fluoridation in the USA. I guess Kennedy wants to Make America have Cavities Again. Of course, water fluoridation is controlled by local and state agencies, so Kennedy may not have much power to regulate it.

This post will examine and critique this new paper. I don’t think you will be impressed with it.

Why is fluoride so important?

Fluoride is the naturally occurring inorganic anion of fluorine. It has one negative charge and is found in fairly large quantities in the form of calcium fluorite (CaF₂), the most common form of fluoride.

Fluoride has a straightforward mechanical effect on teeth and dental caries (commonly known as cavities). Fluoride operates on tooth surfaces by reducing the rate at which tooth enamel demineralizes and increasing the rate at which it remineralizes in the early stages of dental caries. In other words, it reduces the damage to teeth from cavities, but it also can repair it, as long as it is done early enough.

Water fluoridation works by increasing, very slightly, the concentration of fluoride in the saliva, which constantly bathes the teeth with very low levels of fluoride. And by doing so, it reduces the risk of cavities, while also inducing some tooth repair. Please note that if a tooth has significant damage from a cavity, fluoride will probably not repair it. Fluoride is not something where a little helps, so a lot must help a lot.

The World Health Organization states that the upper safe limit of fluoride in drinking water is 1.5 mg/L. On the other hand, the US Environmental Protection Agency (EPA) allows up to 4 mg/L, And the US Public Health Service recommends a fluoride concentration of 0.7 mg/L, which is what most public water systems in the US follow. However, levels above 1.5 mg/L are found in wells and some community water systems.

Fluoride in water and IQ paper

In a paper published on 6 January 2025 in JAMA Pediatrics, Kyla Taylor, PhD, National Institute of Environmental Health Sciences, Morrisville, North Carolina, and colleagues performed a meta-analysis of 59 studies that included 20,932 children with group-level measures of fluoride in drinking water, dental fluorosis, or other measures of fluoride exposure.

Here is the key result of the meta-analysis:

• The pooled standardized mean difference (SMD) of −0.45 for higher versus lower exposure groups roughly translates to a difference of 7 IQ points on a scale with a mean of 100 points.

However, the authors warned that there were limited data and uncertainty in the dose-response association between fluoride exposure and children’s IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L, In other words, at the fluoride levels found in US public drinking systems, 0.7 mg/L, the researchers could find no association between fluoride and IQ.

In an accompanying editorial also published in JAMA Pediatrics, Steven Levy, DDS, MPH, University of Iowa, Iowa City, IA, argued:

…despite the presentation of some evidence of a possible association between IQ and high fluoride levels in water, there is no evidence of an adverse effect at the lower water fluoride levels commonly used in CWF [community water fluoridation] systems. Therefore, public policy concerning the addition of fluoride to community water systems and recommendations concerning the use of topical fluoride in its many forms should not be affected by the study findings and the widespread use of fluoride for caries prevention should continue.

Another issue with this study is that the researchers used urine fluoride measurements to assess fluoride levels in the body. However, urine levels of fluoride can vary over a day or day to day.

Dr. Levy also criticized this assessment:

There is scientific consensus that the urinary sample collection approaches used in almost all included studies (ie, spot urinary fluoride or a few 24-hour samples, many not adjusted for dilution) are not valid measures of individuals’ long-term fluoride exposure, since fluoride has a short half-life and there is substantial variation within days and from day to day.

One other issue with this study is the high level of bias that even the authors admit. Of the 59 studies included in the meta-analysis, 47 had a high risk of bias while 12 had a low risk. Among the 47 studies with a high risk of bias, the difference in mean IQ between high-exposure and low-exposure groups was -0.52.

Among the 12 studies at a low risk of bias, the difference was small, -0.19. Even more, of the 12 studies, eight showed NO LINK between fluoride exposure and IQ. I am not convinced by this study.

More criticism

Furthermore, these researchers are part of the National Toxicology Program group that selected its peer reviewers to self-publish this study as a monograph in August 2024.

But there’s more history than that. Ars Technica wrote:

NTP researchers have been working on the fluoride study since 2015 and submitted two drafts for peer review to an independent panel of experts at the National Academies of Sciences, Engineering, and Medicine in 2020 and 2021. The study failed its review both times. The National Academies’ reviews found fault with the methods and statistical rigor of the analysis. Specifically, the reviews noted potential bias in the selection of the studies included in the analysis, inconsistent application of risk-of-bias criteria, lack of data transparency, insufficient evaluations of potential confounding, and flawed measures of neurodevelopmental outcomes, among other problems.

In other words, this same research was rejected by scientific experts at the most prestigious scientific body in the world because it was just bad. That’s why they self-published the study. I looked at this monograph previously, and I was not at all impressed.

Summary of fluoride in water and IQ

Given all of this criticism, I am wondering why JAMA Pediatrics published this study. It failed peer review with the National Academies, and it appears that the researchers did not add much.

I also want to remind you that water fluoridation is endorsed by nearly every public health organization in the world – the American Dental Association, American Academy of Pediatrics, World Health Organization, and CDC. This represents a scientific consensus on the safety and effectiveness of fluoride in water.

Even though I am entirely unconvinced by this study, the best data they provided linking fluoride in water to IQ was at higher levels of fluoride. They provide no evidence of any value that convincingly suggests that the typical levels of fluoride in water found in the USA have any effect on children’s IQ.

And just in case you want to say “well if a lot is bad, a little might also be bad,” betrays the basic essence of toxicology — the dose makes the poison. Water itself can be toxic if given in high enough doses. That’s why we look at dose-response studies, because at lower doses, a toxin may have zero effect. That’s what we see with fluoride and IQ dose response.

This is just a bad study that is providing “evidence” to people like Robert F Kennedy Jr to fight water fluoridation. What we will get from this is increasing the rate of cavities with more visits to the dentist. No one wants that, except RFK Jr, but he had a worm eating his brain.

Citations

• Levy SM. Caution Needed in Interpreting the Evidence Base on Fluoride and IQ. JAMA Pediatr. 2025 Jan 6. doi: 10.1001/jamapediatrics.2024.5539. Epub ahead of print. PMID: 39761058.
• Solanki YS, Agarwal M, Gupta AB, Gupta S, Shukla P. Fluoride occurrences, health problems, detection, and remediation methods for drinking water: A comprehensive review. Sci Total Environ. 2022 Feb 10;807(Pt 1):150601. doi: 10.1016/j.scitotenv.2021.150601. Epub 2021 Sep 28. PMID: 34597567.
• Taylor KW, Eftim SE, Sibrizzi CA, Blain RB, Magnuson K, Hartman PA, Rooney AA, Bucher JR. Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatr. 2025 Jan 6. doi: 10.1001/jamapediatrics.2024.5542. Epub ahead of print. PMID: 39761023.
• U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Public Health Rep. 2015 Jul-Aug;130(4):318-31. doi: 10.1177/003335491513000408. PMID: 26346489; PMCID: PMC4547570.