FDA can’t stomach fluoride and doesn’t want you to, either

On May 13, the Food and Drug Administration (FDA) announced that it would begin a process intended to exclude ingestible prescription fluoride products for children from the market. Already in 2025, two states have passed statewide prohibitions of fluoridating water, meaning the use of supplemental fluoride prescriptions will be even more important going forward.

How is supplemental fluoride different from fluoridated water?

People’s teeth are constantly being damaged both physically and chemically. These forces destroy the enamel. When fluoride is present in the mouth, it becomes incorporated into the enamel as the teeth undergo the natural degradation and reconstitution associated with digestion. Enamel reinforced with fluoride is stronger and more resilient to degradation than natural enamel, so the presence of fluoride improves oral health. These effects were identified in the 1940s, and the underlying chemical mechanisms have long been understood. A CDC video from 2022 goes into detail about all the specifics, and there are several illustrations of the chemistry around the 30 minute mark.

The primary method by which fluoride is applied to teeth is topical, through toothpaste and in drinking water. In most cases, fluoridated water and toothpaste provide enough fluoride to generate all the benefits of the fluoride without causing any harm.

However, in some areas, water may not be fluoridated to the appropriate level, and fluoride supplements can be beneficial. Fluoride is even more important for children. As their adult teeth develop, having fluoride present in their system helps strengthen their teeth permanently than just using topical treatments like toothpaste and fluoridated water in adulthood.  

The table below shows the current recommended fluoride supplement depending on age and amount of fluoride in water. For children under 6 months, there have been no proven benefits of fluoride, and supplemental fluoride should not be provided. If fluoride content in water is greater than 0.6 parts per million already, supplemental fluoride is unnecessary. The standard in the US is 0.7 parts per million. The largest recommended amount for the supplement is 1mg per day for children between 6 and 16 years old.

Sodium fluoride is one of the most prescribed drugs in the US, with more than 1.7 million prescriptions per year for 771 thousand patients.

FDA evidence

In its press release, the FDA cited five studies to support the contention that fluoride supplements may be harmful. The primary concern seems to be how ingested fluoride affects the gut microbiome in children. Microbiome is technical jargon that represents all the processes that are going on in your digestive system, including the (natural) chemicals and common bacteria that break food down into resources that the body can transport, absorb, and employ.

When fluoride is ingested, it will naturally be broken down from its original form and distributed through the body before making its way to the developing teeth. So, as a matter of chemistry, it will have to affect the microbiome. The FDA is concerned, though, that fluoride will significantly and adversely affect the operation of digestion. The evidence they cite, however, doesn’t show that this would be the case, especially at the levels of fluoride that are relevant.

Only the first two studies explore effects on the microbiome at all. The first study listed did not consider any research on the microbiomes of humans, only animals. It even stated outright “The effects of ingestion of these formulations on the gut microbiome have not been investigated.” In general, substantial adverse effects were only detected at very high dosages.

The second study reviewed 49 studies—42 on animals and four on humans. It generally found that low concentrations (like what we’re exposed to through water or supplements) didn’t create any harm, and may have been beneficial, but extremely high dosages, at least 10 times the standard human exposure “could increase…some unhealthy microbes.”

The FDA announcement also suggests that fluoride may affect IQs as fluoride could potentially interfere with brain development. It includes a study that purports to show such a relationship exists, but not at concentrations below 1.5mg/L (more than double the concentration in drinking water). Furthermore, there are several reasons to discount the result. These studies are not causal, only relational. This means they did not measure the effects of fluoride, but the coincidence of IQ and fluoride consumption. Additionally, more than 60 percent were conducted in China, another 20 percent in India and Pakistan. None were conducted in the US. The effect on IQ they determined, even at higher concentrations, was very low, around 1 IQ point. Finally, these studies were all conducted on fluoridated water, not supplements. There’s no reason to use this study to restrict usage of supplements specifically.

Similarly, a study of fluoride’s effect on thyroid hormones found no effects in the targeted range of fluoride concentration. Effects only showed up at levels three times the size of this acceptable range. The final paper cited again has nothing to do with supplemental fluoride, only fluoridated community water. Many of the criticisms mentioned previously apply here as well; the study is not randomized but only relational. It considered only the effect of fluoridation on dental health, not the microbiome or other adverse consequences. Even with the narrower scope, the authors were reluctant or unable to draw conclusions. This study provides no support for the FDA’s decision to regulate supplemental fluoride.

The bigger picture

Fluoride has been used in humans for 80 years, and in all that time, there has been no research or real-world event that would suggest that it is detrimental to human digestion at typical levels. In light of this lack of evidence, why the FDA is initiating this crusade to eradicate it is inexplicable.

The MAHA Report focused on children’s health and named several concerning health trends. While the FDA doesn’t tie supplemental fluoride to any of these trends, the fact that fewer than one million children use these supplements suggests that it cannot be responsible for them and should not be a priority (or even a consideration) of the FDA.

One of the studies pointed out that the perfect microbiome has not been characterized, meaning even the most expert scientists don’t know what the optimal biome for human digestion looks like. While the paper presumes that there is such a thing, in fact, a human microbiome will probably defy any one-size-fits-all approach. No two people have the same fingerprint, or any number of other biological markers, so why would we expect there to be a perfect microbiome?

With all the variation in human biology, the effects of fluoride on the microbiome are so small, even if someone were to try to measure them, it would likely be impossible to identify the signal from the noise.

Unsatisfied with its failed attempts to regulate the economy and the environment, now government wants to try its hand at regulating the millions of chemical reactions going on in the bodies of hundreds of millions of Americans. This literal micromanagement is too much for any of us to stomach.