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Comment by cheeseomlit | Hacker News Reader

My understanding is that fluoride is supposed to be applied topically, not ingested (hence the poison control warnings on toothpaste packaging). I'm also curious to what extent research has been done all the other things fluoridated water is used for- bathing, cooking, pets, plants, etc.

And the perverse incentives involved make me innately distrustful- the source of the fluoride for example (per this page that has apparently been removed from cdc.gov)

https://web.archive.org/web/20240223213812/https://www.cdc.g...

>The three fluoride additives used for water fluoridation are derived principally from phosphate fertilizer production.

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Your fluoride toothpaste has much, much more fluoride in it per gram than municipally fluoridated water does. That, along with a bunch of other additives, is why it has a poison control warning.

(A typical dab of fluoridated toothpaste has roughly as much fluoride as 2L of municipally fluoridated water.)

The "it's a side product of industrial processes" argument is emotively salient for a lot of people. But it's worth noting that a lot of things are industrial side products: you presumably don't believe that bran is dangerous just because it's by-produced by milling flour.

Children have less fluoride in toothpaste, they also tend to just eat or swallow the toothpaste.

I have seen many times this argument about children who cannot be taught that the toothpaste must not be swallowed, but I am skeptical about how many such children exist.

As a small child, I certainly did plenty of stupid things, but none was of this kind. Perhaps that was due to the fact that my parents never imposed arbitrary prohibitions, but they always explained why it would be bad to do something that was forbidden for me. So if they said that toothpaste must not be swallowed, because it is toxic, I never swallowed it.

Therefore I believe that if there exist such children who swallow toothpaste, that is entirely the fault of their parents. This is not a more normal behavior than eating stones or any other objects. Any children who are old enough to be able to wash their teeth by themselves should be old enough to know what may be eaten and what must not be eaten.

I had a strawberry toothpaste as a child that had delicious flavor and consistency similar to other sweets. Cannot blame the parents for me eating small amounts of it on occasion. At least I'm pretty sure it was fluoride free.

>Any children who are old enough to be able to wash their teeth by themselves should be old enough to know what may be eaten and what must not be eaten.

My experience has been the opposite, it’s very common for kids to try to eat everything including toothpaste. you do your best to try to teach them not to do it, and use a low/no fluoride toothpaste in the meantime.

Right? They make it taste good[1]. Kids eat stuff that tastes good.

[1] https://www.target.com/s/kids+toothpaste

I doubt it's a conscious choice. I am an adult and I avoid toothpaste with fluoride because no matter what I do, once toothpaste gets to the back of my tongue it simply falls into my throat. I would imagine that for a child without decades of swallowing food it's even harder to control or even notice.

My kids ate toothpaste. At the same time I met a guy (still a friend today) who believed somewhat that fluoride was a mind-control thing. I decided I needed more mind control, so I stopped trying to get them to stop. It didn't help, however the kids seem OK today.

Worth reading this silly thread to hit this gem.

Hope you have a great day!

I don’t know of any public sources suggesting that children tend to do either of those things. Anecdotally, I definitely did not eat or swallow toothpaste as a kid.

Kids definitely eat toothpaste when they're young. My source is having children.

Absolutely. My older boy (3 y/o) definitely has eaten it and doesn’t quite get yet why he shouldn’t. I think the comments saying kids don’t do this or it’s the parent’s fault are from people who don’t have kids!

Fluoridated water is literally all around us in naturally occurring springs and drinking water humans have used for thousands of years. Generally speaking, we have a very good idea of what the benefits are and what our general tolerance is for fluoridated water.

That is true and that is why it is known that in the regions where the natural water has a high content in fluoride it affects negatively the bones of the humans who live there.

The reasons why adding fluoride to drinking water is extremely stupid are that there exists no evidence whatsoever that the ingested fluoride can have any beneficial effect on teeth, there exists no known mechanism through which ingested fluoride can have any beneficial effect (the enamel of the teeth does not have blood vessels), but there is ample evidence that too much ingested fluoride is harmful.

All the evidence about beneficial effects of fluoride is about the external contact between teeth and fluoride, when the fluoride ions substitute the hydroxide ions in enamel. This is a simple chemical reaction, it is not a biological reaction mediated by an enzyme.

This beneficial effect is achieved best by the use of toothpaste or mouth washes with fluoride, which can provide much more fluoride than it would be safe to ingest. It is impossible to optimize the concentration of fluoride in drinking water for a maximum effect on teeth while not being harmful after ingestion, because the amount of water that is drunk daily is variable and unpredictable.

Moreover, the fluoridated drinking water would have a much greater beneficial effect if one would keep the water in the mouth for some time before swallowing it, which nobody does, so most of the fluoride in the drinking water has no opportunity to provide any beneficial effect.

"there exists no evidence whatsoever that the ingested fluoride can have any beneficial effect on teeth"

That is simply wrong. When fluoride comes into contact with developing teeth, it incorporates into the enamel crystal structure, forming fluorapatite, which is more resistant to acid attacks from bacteria that cause cavities.

> exists no evidence whatsoever that the ingested fluoride can have any beneficial effect on teeth

This is just objectively wrong. We've known for almost a hundred years now that ingested fluoride reduces dental problems. Literally the entire reason why fluoridation of water got started was because scientists noted that in regions with higher than average naturally occurring fluoride levels in water resulted in fewer caries.

Very false.

That is not evidence that ingested fluoride reduces dental problems.

When the water with fluoride is drunk, the fluoride ions come in contact with the teeth and a very small fraction of them succeed to substitute hydroxide ions in the enamel before the water is swallowed.

After the water is swallowed the only way for fluoride to reach again the teeth is when a very small fraction of the ingested fluoride exits again the body into saliva.

Both these actions, from the water while it is drunk and from saliva are extremely inefficient in comparison with the use of toothpaste with fluoride, because only a very small part of the fluoride introduced in the drinking water has the opportunity of interacting with the teeth.

When fluoride is inside the body, it does not have any beneficial effect, but it can interfere with the growth of bone tissue and it may have other less understood harmful effects. The body can deal with fluoride intakes that are not excessive, mostly by eliminating it into urine, but the fact that we can tolerate fluoride in small quantities cannot be an argument for introducing it intentionally in our bodies.

There is very strong population-scale evidence that municipal fluoridation significantly reduces the incidence of caries in children, including in developed countries with strong conventions around dental health (brushing twice a day, flossing, etc.)[1][2].

(A lot of this research comes from comparing cities/communities in Canada, since Canada is among the few countries that have gone on-again, off-again with municipal fluoridation. This in turn makes the data really strong, since there are relatively few confounding factors when comparing dental outcomes between Canadian children, versus children spread across the world.)

Of note: the research also indicates that, if the general public were to brush twice a day with fluoride toothpaste, then municipal fluoridation would probably have only a marginal effect on overall dental health outcomes. But there's no strong evidence that redirecting money away from municipal fluoridation towards dental health education would meaningfully move the needle on individual practices; to the contrary, there's strong evidence that a decent percentage of the population will never engage in baseline dental hygiene, and thus benefits disproportionately from municipal fluoridation.

[1]: https://www.researchgate.net/publication/335773400_Affirmati...

[2]: https://onlinelibrary.wiley.com/doi/10.1111/cdoe.12685

I'm fairly conspiracy-minded, but fluoride is prescribed for ingestion in some cases: https://en.wikipedia.org/wiki/Fluoride_therapy

I was prescribed fluoride tablets by my dentist as kid.

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