AMA #15: Fluoride Benefits/Risks & Vagus Nerve Stimulation

This Ask Me Anything episode belongs to the Huberman Lab premium subscriber channel. Huberman says the channel exists to support the free weekly podcast and to fund human research on mental health, physical health and performance at Stanford and elsewhere. He adds that the Tiny Foundation has agreed to match every dollar the premium channel generates for research studies, which doubles the total funding.

The first listener question asks why fluoride is in drinking water and "how much is it harming us?" Huberman objects to the framing before he answers. He says the question presumes harm, while whether fluoride hurts you depends on how much of it is in the water, toothpaste or other things you consume. He grants clear benefits for tooth strength and cavity prevention, but says that too much fluoride is dangerous and "a poison at certain levels."

So as you've probably heard before, the dose makes the poison.

Huberman says even the "why" part is hard to answer cleanly because of what was happening in 2024. In California, a group that believes fluoride at any concentration in drinking water is bad had filed a major lawsuit to get it removed. He says the outcome was still undetermined. As the basis for their concern, he cites evidence that fluoride above a certain threshold can cause problems with thyroid hormone function and perhaps some aspects of brain function, and he repeats the threshold caveat.

At the same time, he says, citizens in Buffalo, New York were suing their city for the opposite reason. They claimed the water did not contain enough fluoride and sought damages for their children's dental health needs. Huberman notes that some areas of the United States have low or perhaps zero fluoride in their water. He says Buffalo may since have raised its level from zero, but that whether it was actually zero "is still debatable."

He uses these opposing cases to show how far apart people are on whether fluoride in water is safe. Some people sue because there is too little and others because there is any at all. He calls it a topic where you are likely to get stuck from any angle.

So this is a really barbed wire topic, as I like to say.

Setting dosage aside, Huberman explains why fluoride is used at all. He promises more detail in a future oral health episode. He says teeth are always in a state of demineralization or remineralization, which he shortens to "demin" and "remin," with one or the other predominating. A cavity forms when bacteria, especially Streptococcus mutans, feed on sugars in the mouth. As a byproduct, they produce acids that erode the enamel and deeper layers of the tooth, demineralizing it.

Remineralization runs the other way. Minerals build crystals that stack in organized sequences, which he compares to LEGO blocks. He says this process can potentially fill in small cavities that have not yet reached the deeper layers. The critical element in these blocks is hydroxyapatite.

Huberman stresses that fluoride is not a vitamin or an essential nutrient and is a poison at high concentrations. Its value lies in its ability to get inside these crystal chains and form bonds that are stronger than the hydroxyapatite bonds that would normally form. Drinking fluoridated water or using fluoride toothpaste, especially in childhood, therefore makes the tooth's mineral structure "super physiologically strong." That limits the ability of Strep mutans and its acid to erode enamel and cause cavities.

Huberman says he asked several dentists and a periodontist why fluoride is in water and toothpaste. They gave him the chemical-mechanical rationale above. He then draws a distinction. Most health inputs, like diet and exercise, are individual choices. Tap water, by contrast, is basically a government or local government-supplied resource that reaches everyone who drinks from the tap.

He describes the policy logic. He believes it first took place in the 1950s, though he states this tentatively. Because fluoride can make teeth super physiologically strong, authorities added it to drinking water to reduce cavities and tooth decay in children and adults. He says he was told this was not necessarily the best way to care for teeth. It was and remains a fairly low-cost approach for cities, and he notes that practices vary around the world. He also says other measures can improve tooth mineralization and even fill cavities that have not reached the dentine layer, even with no fluoridated water or toothpaste, and defers the details to the future episode.