What Fluoride Does Once It Gets Past the Teeth

For most of my life I filed fluoride under settled and boring. It hardened enamel, it went in the tap water, the argument about it ended somewhere around my grandmother’s generation. That tidy story is not holding up, and right now it is coming apart in public, in a fight over whether the stuff should stay in American tap water at all.

The first crack most people noticed was in the brain. In 2024 the U.S. National Toxicology Program concluded, with what it called moderate confidence, that higher fluoride exposure is associated with lower IQ in children, and it drew its line at more than 1.5 milligrams per liter of water. The U.S. recommends 0.7 mg/L for the systems that fluoridate, roughly half that, so the dental establishment filed the finding under somebody else’s problem in somebody else’s wells. What is harder to file away is that the review sat in bureaucratic limbo for years before it was published.

The finding that actually made me put my coffee down is quieter, and it has nothing to do with the brain. In August, researchers publishing in Environmental Health went looking where fluoride is not a hypothetical: Yazd, in central Iran, where it saturates the groundwater. They measured the fluoride in the drinking water and the fluoride in the children’s urine, then set both against the kids’ cardiovascular risk factors. Their premise is one every parent should sit with: the biology that becomes adult heart disease, the blood pressure that runs high, the lipids that drift wrong, is laid down in childhood and carried forward. So why would a mineral we think of as a tooth thing turn up anywhere near a child’s heart?

That question only makes sense once you see the doses. Central Iran sits on fluoride-rich groundwater, and the numbers there put American fluoridation in a different light. The U.S. recommends 0.7 mg/L. The WHO sets its health-based limit at 1.5 mg/L. In Ardakan, in Yazd province, the mean hits 2.92 mg/L and climbs as high as 6, with more than half the sampled villages over the WHO line. These children are living the long, high-dose experiment no American review board would ever approve.

Here is where the biology stopped being boring for me. Fluoride is swallowed, absorbed through the gut, and most of what the body holds onto ends up parked in bone and the other tissues that mineralize. So ask the obvious question. If the ion likes to settle into anything that hardens, what is it doing as it rides past artery walls, which calcify too as we age? The leading hypothesis is that chronic exposure drives oxidative stress and pushes vessels toward stiffness, so the same chemistry that hardens enamel may be working, quietly, on a blood vessel. The body does not keep one filing cabinet for teeth and another for arteries. That is the moment the whole thing clicked for me, and not in a comforting way.

And Yazd is not a lone data point. In the Mexican PROGRESS birth cohort, which followed roughly 500 children, each doubling of early-childhood fluoride intake tracked with worse cardiometabolic markers in the years that followed: triglycerides climbing about 2 percent a year, total cholesterol up 1.46 mg/dL a year, and HbA1c, the running average of blood sugar, up 0.76 percentage points a year. In a body that is still being built, those are not rounding errors.

Blood pressure shows the same shape in the high-exposure data. A 2021 systematic review and meta-analysis pooling six studies from fluoride-endemic regions found systolic pressure running 6.49 mmHg higher, and diastolic 4.33 mmHg higher, in high-fluoride populations than in low. Those studies lean adult, not pediatric, so read them as the destination rather than the childhood snapshot. This looks like where the vessels end up.

Here is the evidence that cuts the other way, and it does not say nothing to see. At the 0.7 mg/L Americans actually use, the signal mostly vanishes. An analysis of NHANES data on children aged 6 to 19 found no significant blood-pressure difference across fluoride levels, and a large German survey of children and adolescents came up essentially empty, save a weak inverse blip in HbA1c. So the honest pattern is not harmless versus poison. It is that the cardiometabolic harm shows up loudly where the dose is high and fades where the dose is low. Dose is the whole ballgame, and dose is exactly the question the American fight has never cleanly answered.

Because the timing is not subtle. In April 2025 HHS Secretary Robert F. Kennedy Jr. said he would direct the CDC to stop recommending fluoridation, the EPA announced it was reviewing the science, and Utah became the first state to ban it outright. The reflex from the dental and public-health establishment was immediate and familiar: settled, safe, move along. But settled is a strange word for a question these same institutions left sitting in a drawer for years while the IQ evidence and the endemic-region cohorts piled up. When the people assuring you a dose is safe are the ones who were slow to read the file, trust us is not a dosing study.

I am not worried about the fluoride in your toothpaste. Spitting it out is a different proposition from swallowing it every day for eighteen years while your arteries are still under construction. But having chased this all the way down, I filter my drinking water, and if I had a young child I would not wait for a reconvened task force to bless a dose before I stopped pouring it into a growing body every day. The burden of proof sits with the people who put it in the water, not with the parent asking what it does once it gets past the teeth.

Sources

1. Environmental Health – urinary and water fluoride vs. cardiovascular risk factors in children and adolescents, Yazd (2026)
2. Environment International / PROGRESS cohort – early-life fluoride and cardiometabolic outcomes in Mexican children (2023)
3. Int. Arch. Occup. Environ. Health – fluoride in drinking water and blood pressure, systematic review and meta-analysis (2021)
4. National Toxicology Program monograph – fluoride exposure, neurodevelopment and cognition (2024)
5. Int. J. Environ. Health Research – fluoride exposure and blood pressure in U.S. children aged 6 to 19, NHANES 2013–2016
6. Fluoride status and cardiometabolic health, representative German survey of children and adolescents
7. Data in Brief – fluoride concentrations and health-risk assessment, Ardakan, Yazd province, Iran
8. CNN – HHS/EPA to study fluoride as RFK Jr. moves to end CDC recommendation (2025)