Influencer Gary Brecka spreads misinformation about water fluoridation in Instagram post

In April 2025, U.S. health secretary Robert F. Kennedy Jr. announced that he would tell the Centers for Disease Control and Prevention to cease recommending water fluoridation. This followed another announcement by the U.S. Environmental Protection Agency (EPA) that it would review “new science” on the potential health risks of water fluoridation.

Fluoride is naturally present in water at varying levels. But many countries around the world practice water fluoridation, in which more fluoride is added to drinking water in a controlled manner, as one approach to fighting cavities and reducing tooth decay. Despite its proven public health benefits, some groups have campaigned for a halt to community water fluoridation, alleging that it causes harm. Secretary Kennedy himself has claimed that fluoride poses health risks, calling it a neurotoxin. NPR traced these claims back to conspiracy theories about fluoride that circulated during the Cold War.

For the record, experts don’t consider community water fluoridation programs to be harmful. On the contrary, the American Dental Association, the American Academy of Pediatric Dentistry, and the American Academy of Pediatricians consider water fluoridation to be critical to fighting caries and tooth decay.

Kennedy isn’t the only one who has spread misinformation about fluoride; the theme is also popular with various health influencers. In an Instagram post published on 28 March, “human biologist” Gary Brecka claimed that fluoride is a “neurotoxin” and is linked to “lower IQ in children, thyroid dysfunction, and weakened bone density”. That post received more than 40,000 likes.

Brecka, who claims to be a researcher and “an anti-aging and longevity expert”, holds two Bachelor of Science degrees in biology—one from Frostburg State University and the other from the National University of Health Sciences (National College of Chiropractic)—but no advanced qualifications or research experience.

Brecka previously spread false claims about folic acid supplementation in food and about thyroid disease. He also sells various products that allegedly boost health on his website “The Ultimate Human”, even though little to no evidence backs up these claims.

No evidence fluoride levels used in community water fluoridation linked to lower IQ in children

The claim that fluoride reduces IQ in children is a longstanding one in anti-fluoridation circles; a Snopes fact-check of this claim dates back to 2017. Science Feedback discussed iterations of this claim in greater depth in previous reviews; we invite readers to explore these reviews for more details.

To summarize, the evidence for fluoride’s allegedly neurotoxic effects mainly revolve around animal studies and a review of 27 studies^[1] that looked at associations between industrial chemicals and neurodevelopmental disorders.

There are caveats to these studies. Firstly, what happens in animals doesn’t necessarily predict what happens in humans. Secondly, the changes observed in these studies were associated with fluoride levels far greater than that used in community water fluoridation (the recommendation in the U.S. is 0.7 milligrams per liter). Put simply, these studies aren’t relevant to community water fluoridation which uses much lower doses of fluoride.

As the saying goes, the dose makes the poison, and anything can be harmful in large enough doses, even water.

A more recent iteration of this claim co-opted a monograph from the National Toxicology Program, run by the U.S. Department of Health and Human Services. An earlier Science Feedback review explained that while the monograph reported a correlation between reduced IQ and high levels of fluoride in drinking water, the amount of fluoride used in community water fluoridation programs is much lower.

Lack of evidence supporting claim that water fluoridation leads to weaker bones

It’s unclear what evidence Brecka based his claim about “weakened bones” on, but it’s possibly a reference to the condition known as skeletal fluorosis.

Skeletal fluorosis is the result of chronic, excessive fluoride exposure. Over time, this leads to changes in bone structure that weaken bone, making it more brittle and easier to break. The condition is associated with geographical areas where naturally occurring fluoride levels in water are very high, for example, in India and China.

In rare cases, consuming very large amounts of tea over prolonged periods of time has also been linked to skeletal fluorosis^[2,3].

Because excessive fluoride exposure comes with health risks, regulatory bodies set limits on the amount of fluoride that’s allowed in water. For example, the EPA considers 4 milligrams per liter of fluoride in water as the “maximum amount that is allowed in water from public water systems”. The U.S. National Academies reviewed evidence on fluoride’s health effects in 2006. The epidemiological evidence reviewed suggested that skeletal fluorosis is more likely to occur when fluoride levels in drinking water reaches 4 mg/L and above.

The optimal amount of fluoride needed to prevent dental cavities, according to the U.S. Public Health Service’s recommendation, is even lower than that threshold: 0.7 milligrams per liter, or nearly six times lower.

Simply put, while ingesting too much fluoride can result in skeletal fluorosis, the likelihood of this occurring because of community water fluoridation is little to none.

Lack of evidence for claim that water fluoridation causes thyroid dysfunction

Again, Brecka didn’t present evidence for this claim, but a similar claim made headlines in 2015, after a study by researchers in the UK reported a correlation between fluoride levels in drinking water and hypothyroidism (underactive thyroid) prevalence^[4]. Thus the study may be the basis for Brecka’s claim.

However, the study was criticized by other scientists as being methodologically weak. One of the main issues is that it relies solely on a correlation to establish a causal relationship.

But there are many risk factors for hypothyroidism that the study didn’t account for, also known as confounding factors. These are variables that affect the outcome of an experiment, but aren’t the variables being studied in the experiment. Failing to account for the effect of confounding factors could lead researchers to arrive at incorrect conclusions.

David Coggon, a professor of occupational and environmental medicine at the University of Southampton, told Science Media Center (SMC):

“As epidemiological evidence goes, this is about as weak as it gets […] It is quite possible that the observed association is a consequence of other ways in which the areas with higher fluoride differ from the rest of the country. There are substantially more rigorous epidemiological methods by which the research team could have tested their idea”.

When interviewed by The Conversation, Peckham defended the study as “comprehensive and methodologically solid”.

Sandra White, the then-director of dental public health at Public Health England, told SMC that “​​[t]he totality of evidence, accumulated over decades of research, tells us that water fluoridation is a safe and effective public health measure, and shows no association with reduced thyroid function”.

We reached out to Brecka for comment and will update this review if new information becomes available.

Conclusion

Community water fluoridation is practiced in several countries as a public health measure against tooth decay. Claims that water fluoridation is harmful are typically poorly founded, relying on studies where the fluoride levels examined were much higher than those used in water fluoridation or which didn’t adequately rule out the effect of confounding factors on the outcomes studied.

REFERENCES

• 1 –  Choi et al. (2012) Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis. Environmental Health Perspectives.
• 2 – Izuora et al. (2011) Skeletal fluorosis from brewed tea. Journal of Clinical Endocrinology and Metabolism.
• 3 – Kakumanu and Rao. (2013) Skeletal Fluorosis Due to Excessive Tea Drinking. New England Journal of Medicine.
• 4 – Peckham et al. (2015) Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. Journal of Epidemiology and Community Health.