How Do I Keep My Kid from Swallowing Fluoride?

My 2-year-old is swallowing fluoride toothpaste after brushing. Pediatricians and dentists insist on fluoride over non-fluoride toothpaste to prevent cavities. I’ve seen studies about the effects of fluoride in water on brain toxicity and lowering IQ, but not on toothpaste. Should I be worried about her brain development?
—Maria

We can dispense with the benefits first here. There are significant benefits to fluoride for preventing cavities. We have a lot of evidence on this. Non-fluoride toothpaste is better than nothing, but adding fluoride improves cavity prevention.

Of course, there are these fluoride concerns. Most or all of the evidence on this comes from water fluoridation studies.

As you note, there is an active literature on the question of whether fluoride in drinking water lowers IQ. I’ve written about this before, back in 2014. Since then, the primary study that raised concerns (a study in China) was retracted for a flawed methodology. One new study has come out on fluoride in pregnancy and child IQ, which has somewhat mixed results (small negative coefficients for boys, small positive coefficients for girls). A second study argues that there are reductions in IQ for formula-fed babies who are exposed to fluoridated water, but their estimates appear to be driven by two outlying data points.

This issue probably deserves more time than a Q&A answer here, but the bottom line is it’s a confusing set of evidence to fully parse. On the whole, though, I would say it’s very hard to build a strong case for any dangers of water fluoridation.

Fluoride exposure in toothpaste is potentially subject to similar concerns. A difference is that, for adults, you do not swallow the fluoride in toothpaste. So while you get a little exposure, it’s small relative to (for example) your water-based exposure. Kids do sometimes swallow toothpaste. However: if you use the appropriate amount of toothpaste, the exposure is still quite minimal.

A rice-grain-size amount of toothpaste (which should be all you need for a 2-year-old) is going to have about 0.3 milligrams of fluoride in it. Even if they swallow the whole thing, this is only half of what a typical liter of water would have in it. In other words: toothpaste exposure, even for a chronic swallower, is a relatively small part of their overall fluoride intake. And, again, there’s really no strong evidence for fluoride being an issue.

I’d try to stop worrying about this. She will learn to spit out toothpaste eventually!