Dissecting a Fear-Mongering Instagram Square

A closer look at exaggerated claims about fluoride and IQ seen on social media

A friend of mine recently sent me a screenshot of this Instagram post, asking what I thought about it. While I’m no toxicologist, I do know a lot about IQ, so I figured I had enough background knowledge and context to dig in and offer my perspective.

First, I checked the Instagram post to see if there was a link to the study itself. Negative. A quick Google search, however, brought me to what I assume was the report he referenced. Right away, I could see it met a lot of quality markers. It’s a comprehensive review of the literature, synthesizing results across many studies, rather than a single, isolated report. It’s produced by the National Toxicology Program at NIEHS, so it’s written by trusted experts. It’s peer-reviewed by a number of heavy hitters in the field. It’s really hefty (300 pages!) with robust citations and clear methodology, results, and conclusions sections. It’s definitely a document to take seriously.

Then, as I read further, I thought more critically about the study’s findings. Methodologically, it was sound; it’s an exhaustive review that searched the literature thoroughly and assessed each study’s quality rigorously. And it provided compelling evidence linking fluoride exposure to IQ reductions in kids. 

But the IQ reductions the studies showed, though significant (i.e. not due to chance alone), were really small: the most extreme were around 5 points. To put this into perspective, IQ has a standard deviation of 15 points; in terms of adult height, that’s comparable to a difference of about 1 inch—not particularly meaningful for most people.

And, interestingly, none of the included studies were from the United States. Recognizing that different countries have different fluoride regulations, I compared the fluoride levels studied with those in New York City tap water. Fluoride levels in the report were about twice as high as what’s found here, and, crucially, lower fluoride levels consistent with our exposure were not linked to IQ reductions.

So I responded to my friend by saying this: The benefits of fluoride for preventing tooth decay are well documented. If I had to choose between protecting my teeth and sacrificing a few IQ points, I’d probably choose the teeth. But given that our fluoride levels are below those associated with IQ effects, I don’t think we need to worry.

As with many substances, dose matters. Advil helps my headache, but taking ten Advil at once isn’t safe. Similarly, fluoride benefits my teeth, but only in the right amounts. Research like this is valuable for guiding optimal exposure levels so regulations can adapt responsibly—not to fuel influencer-doctors’ fear mongering for more followers. 

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She’s perfect!