Major Flaws in 2025 Meta-Analysis on Fluoride and Children IQ Scores | Hacker News Reader

Major Flaws in 2025 Meta-Analysis on Fluoride and Children IQ Scores

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103 pointsjandrewrogers84 comments

It is not that expensive to run double-blind fluoride experiments. There are hundreds that have been run over decades. There is a Scotland that the found an 81.4% reduction in cavities. A double-blind study from New Zealand found no benefit to osteoporosis is postmenopausal women. Etc. Etc.

If these neurocognitive effects were actually measurable, they wouldn't need to cherry-picking population-level correlation studies to find effects that are within the margin of error of the tests.

> There is a Scotland that the found an 81.4% reduction in cavities.

Do you have a reference?

"Hi we would like to give your child something that we think will lower their intelligence would you sign here please."

> we would like to give your child something that we think will lower their intelligence

“The association between drinking carbonated drinks, eating chips and intelligence level was significant (P= 0.043, 0.001) and prevalence odds ratio of 1.5 and 2.4 respectively” [1].

Anyone arguing this is about childhood IQ and wouldn’t similarly ban (not stop mandating, ban) soft drinks, chips and fast food for kids, they’re signalling this is about something other than kids’ health.

(Note: this isn’t my mole hill. I think communities should have the right to make this call on their own. And the cited study quality is just as good as the fluoride causes autism ones.)

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC3507933/

Note that you are making a casual claim (that junk food lowers intelligence in children) but the paper you cite provides no evidence of causation, only a statistical association between diet and intelligence scores. Further, this association could be caused by the well known fact that parents who are more focused on their child’s well being are not only more likely to provide a diet more in line with health recommendations (less junk) but also more likely to invest in their child’s educational outcomes.

The parent comment is not making a causal claim. They're pointing out a double standard: "Anyone arguing this is about childhood IQ and wouldn’t similarly ban (not stop mandating, ban) soft drinks, chips and fast food for kids, they’re signalling this is about something other than kids’ health."

In other words, if these people are anti-fluoride because it's supposedly bad for children's IQ, they should also oppose bad food for the same reason. If they don't, the supposed (unproven) health effects are not the reason. That's the point that is made, at least.

Yup. We don't have causal studies on fluoride's effects on intelligence, to my knowledge. This is so obviously not about kids' health, but like MMRs, partisan/social identity signalling.

Even if you believed that to be the case, you could choose an area that had high natural fluoride in the water, provide gravity filters and then double-blind supplement fluoride at a moderate level for one group.

It is certainly more ethical than saying "we are definitely going to let your children's teeth rot because some people think, on the basis of circumstantial evidence, it might have approximately the same effects as not having children's books in the home."

I live in a town where most people grew up on well water, but we grew up in cities in another state with fluoridated water.

When I took my daughter to see a dentist here, the dentist saw my daughter's good teeth during the check-up and said, "You didn't grow up here, did you?"

N = 1 doesn’t work for these effect sizes. Each of brushing frequency, use of proper toothpaste, flossing, diet, hydration and I think even genetics affect dental health more than fluoride. The point is fluoride in water provides a good catch-all if those practices aren’t followed.

The studies on fluoride in drinking water indicate HUGE reductions in cavities. I don't think it's a catch-all, it's just effective.

Water fluoridation is considered very common in the United States, Canada, Ireland, Chile and Australia where over 50% of the population drinks fluoridated water.

Most European countries including Italy, France, Finland, Germany, Sweden, Netherlands, Scotland, Austria, Poland, Hungary and Switzerland do not fluoridate water.

https://en.m.wikipedia.org/wiki/Water_fluoridation_by_countr...

Make your own conclusions.

Is there a solid 'trust this paper' site out there? I would think that something could be built that rated papers on how much they have been reproduced, supported or refuted by other papers.

The Cochrane Library (https://www.cochranelibrary.com/) generally has good meta-analysis on various topics. I often prefer that to any one paper.

Site blocks Tor.

Here is the abstract if you can't load the page normally:

A recent meta-analysis in this journal (Taylor et al 2025) produced ostensible evidence of a negative correlation between fluoride exposure and intelligence in children, which garnered major public attention. There has, however, been criticism of this undertaking and conclusions. In order to address the controversy over this work, we in this special communication undertake an independent forensic meta-science review of the methodology and statistical approaches employed and inferences drawn by the authors, as well as an investigation of the underlying data integrity of the constituent studies. We find that the authors employed unjustified methodological and statistical errors which invalidate their conclusion, and demonstrate that the data cannot be analysed as the authors assert. We further find major problems with the sources employed, including reliance on studies from non-MEDLINE indexed publications with an anti-fluoridation editorial stance, and major underlying issues with the data reported in several instances, indicative of impossible or unreliable data. Taylor et al is not reliable nor are its errors remediable. It should be retracted to avoid harms to public health and scientific discourse.

> Taylor et al is not reliable nor are its errors remediable. It should be retracted to avoid harms to public health and scientific discourse

It’s a bit late for that! “Fluoride makes you dumb” is now established in the public discourse as if it were true.

Look, folks, you're being lied to, and you're victims of pseudoscience, and it's easy to prove using facts and logic, so downvote away at your own peril.

Heavy industry, the dental industry, and your municipalities are lying to you when they say that drinking fluoride helps your teeth.

Now when a dentist applies a fluoride treatment in a paste or appliqué, the solution stays in contact with living bone for a significant dosage time. The process is known as "remineralization" and so there is scientific basis for such a treatment to be effective.

But when you drink water with the same substance, it quickly washes around those bones and into your esophagus. It doesn't stick around. It's like getting a cross tattoo to become Jesus. Fluoride will be digested, and absorbed into your bloodstream, and cross your blood-brain barrier, for sure! But it won't stay adhering to your tooth-bones and the remineralization process never has a chance to start. That's absurd thinking that it somehow is internally effective. It's simply not the mechanism of action. There's not enough time for it to work. The process requires physical contact in order for a chemical reaction to occur!

Fluoride is, however, well-known to produce favorable psychoactive effects. For the past century or more. That's why we got Prozac, where the active ingredient is "fluoxetine". Prozac was the next step forward in getting fluoride to the masses who may not drink black/green tea, or live in fluoridated municipalities.

I have a meta-hypothesis that excess surplus of any product is often remarketed as beneficial. For example, heavy industry produced massive amounts of talc and they were able to parlay it into many products as a powder. I simply feel the same way about minerals such as magnesium. How much Epsom salt is sold, simply because industries need to unload this stuff by the 5lb bag, vs. how good it works in a bathtub, I don't really know. But I literally envision cigar-filled back rooms where executives go "we can profit by digging a lot of this crap out of the ground and putting it on store shelves, or just dumping it right into water supplies, if only there's a way to convince everyone it's good for them!" And there's nothing different with the way lithium's being used, either. It used to be a soft-drink additive! Wait until they begin lithiating all your potable water supplies! (Sort of horrific, because side effects of lithium consumption include polydipsia and polyuria...!)

But fluoride is the biggest scam of the 20th century. It's pseudoscience and quackery that sold it to the general public, and your cities are literally lying through their teeth when they don't tell you their ulterior motive and they pretend that there is "evidence" of beneficial effects on teeth. Nothing could be further from the truth. Y'all might as well believe in phrenology and astrology.

But when you drink <coffee>, it quickly washes around those bones and into your esophagus. It doesn't stick around. It's like getting a cross tattoo to become Jesus. coffee will be digested, and absorbed into your bloodstream, and cross your blood-brain barrier, for sure! But it won't stay adhering to your tooth-bones and the <yellowing> process never has a chance to start. That's absurd thinking that it somehow is internally effective. It's simply not the mechanism of action. There's not enough time for it to work. The process requires physical contact in order for a chemical reaction to occur!

I’m going to let my dentist know this next time they claim that the stains on my teeth may have been caused by coffee or tea.

Sort of absurd that you think that the process of staining is comparable to a remineralization. For one thing, coffee and its colorants are thicker and they’ll adhere for longer. Fluoride is simply an elemental substance, not a molecular solution.

While we’re on the subject of cosmetic appearance: fluoride itself can gradually discolor bones such as teeth, and leave really unsightly dark spots on them; good luck to y’all’s dentists trying to distinguish where y’all’s staining came from, because they ain’t gonna blame King Fluoride for it! [They also can’t scrape off your fluorosis with their hand tools anyway...]

It may not be ineffective to formulate fluoride into a paste or gel and then a medical professional deliberately paints it onto dental caries and then carefully holds it there whilst the chemical reaction takes place: honestly, the longer the better.

But just randomly rinsing your mouth with it and then swallowing all of it immediately is the dumbest fucKing pseudoscience I’ve ever heard, yet AmeriKans have swallowed it hooK, line, and sinKer: Seig Heil, DoKtor Mengele!

There are explanations that sound reasonable to me as to why, as you put it, "rinsing your mouth with it and then swallowing all of it immediately" still has a positive effect on your teeth. Have you looked into those at all, and if so, do you dismiss them all as lies?

Honestly, as long as we’re not collectivising the cost of dental caries, and insurers can discriminate dental pricing based on fluoridation if they choose to, I’m okay with folks who don’t brush their teeth doing whatever they want to.

The problem is that children aren't allowed to choose for themselves. Their parents are able to set their kids up for a life of pain and dental bills the parents don't have to experience or pay for.

For completeness sake that could potentially also cut both ways. If it turns out that fluoride does lower academia potential then it would be occurring in the brain's most important development period. Once they are adults they would have to live with that artificial limitation. Though they do say ignorance is bliss.

My personal preference would be to let the scientists, researchers and skeptics put on boxing gloves and in the mean time give the child a healthy diet, teach them to use a water-pick daily to avoid not only cavities but other potential issues related to diet and gum hygiene.

None of these studies measured academic potential or outcomes.

That's what I mean, if one day they actually study this correctly and have a raging epiphany then it would be too late for kids already subjected to fluoride whereas a healthy diet, good brushing with fluoride free toothpaste and using a water pick could mitigate cavities just fine among other things. Perhaps even mitigate the need for SSRI's, ADHD drugs, etc... but that's a much bigger topic.

> Their parents are able to set their kids up for a life of pain and dental bills

This is true of a lot of parenting, and the case is more critical for vaccines than dental hygiene because cavities aren’t transmissible. (Within reason.)

So yes, ideally the kids of the uninformed wouldn’t be born into dental debt. But that’s better than them having gone blind from measles or lame from polio. (Coldly, because those costs will be socialised.)

Those aren't mutually exclusive.

It is interesting how different these discussions are in countries where children's rights are part of the constitution. It's a quirk of America's history of treating various groups of people as chattel that we have kept that framework for children.

> Those aren't mutually exclusive

Logically, no. Politically, I think so. (Counterargument: fluoride is a bulwark against the idiots. As long as they’re fighting fluoridation, they aren’t as focussed on vaccines. I don’t buy it, but it’s worth raising.)

> a quirk of America's history of treating various groups of people as chattel that we have kept that framework for children

It’s a quirk of the Constitution having been written in the 18th century. Children didn’t have rights in most of the world at that time.

Great. Except fluoridation isn't a per-household choice, it's on the municipality level, so your insurance rates will go up because your neighbors aren't taking care of their teeth, even if you are.

The OP literally said "as long as insurance can discriminate"

That's just not how a society should work. Children should get a fair chance at life no matter how ignorant or negligent their parents are. Fluoridated water keeps teeth in mouths and students behind desks instead of missing school.

This is also true for measles and chickenpox, both of which have quite unpleasant or even lethal medium-to-long-term consequences in some fraction of people who appear to have recovered.

> Children should get a fair chance at life no matter how ignorant or negligent their parents are

I agree in principle. But this just isn’t the country we live in. Smart states and communities can still think this through logically. But it may be for the best to let the antivax rural areas do their own thing and stick to themselves.

The problem is that there is no clear demarcation of the transition from parental control to state control.

Even subjects like corporeal punishment and surgical modification are murky at best. Dental hygiene seems incredibly far down the list.

> Dental hygiene seems incredibly far down the list

Yup. It’s also something that can be mostly fixed later in life. So turning it into a hill to die on seems strategically unwise.

You can't fix the fact that poor dental health is associated with poor school attendance and lower academic achievement, later in life.

>antivax rural areas

I would be careful with what size brush you are painting.

>There are, of course, the familiar anti-vaxxers, who spoke up as early as February with concerns about a mandatory vaccine. There are also new groups. One is connected to far-right extremism and conspiracy theories (about the virus and otherwise). The other, termed “vaccine-hesitant,” is more surprising. It includes members of the opposite demographic — highly educated, liberal, not libertarian

>While a majority of those unwilling to get a vaccine are Republicans, 42% of Democrats agree with them

https://harvardpolitics.com/the-new-anti-vax/

The anti-vaxx movement was really strong among ex-hippies when I was growing up. It's all the same people who believe in homeopathy and chiropractors.

Part of the problem is presenting it as a choice makes people think it is legitimate to choose "no".

I believe the consequence of not vaccinating should be social exclusion until you catch up: anything else is stochastically depraved heart murder.

> I believe the consequence of not vaccinating should be social exclusion until you catch up

I think it should be even stronger than that: no public services or public spaces for you. No driver's license, no public school, no library card, nothing, unless you can demonstrate a medical reason why you cannot receive a specific vaccine, and then you get an exception for only that one.

If you want to live in your own world where you're disconnected from society then that's fine, you can do that, but it doesn't and shouldn't come consequence free given the damage you can do to others.

The vaccine hesitant, to my knowledge, still gave their kids the MMR. They have just been sceptical of newer vaccines, e.g. for Covid or the flue. That’s probably a long-term problem. But it isn’t creating pockets of measles- and polio-afflicted kids.

You’re begging the question. If fluoridation decreases IQ through developmental neurotoxicity, is the lost cognitive capacity in the general population justified by the protection of children with irresponsible parents (who do not enforce eg the brushing of teeth) from the consequences of caries? This is a real moral problem we ought to contend with.

I believe society suffers from lower IQs, and that targeted interventions against childhood caries can be applied effectively without dosing the whole population. Why don’t schools teach toothbrushing? Why not have the school nurse check children’s teeth, or have a dentist come to school periodically?

The point of this article is that the evidence of what you are saying is unconvincing.

Even if it _were_ real science [Note: actual science engages with criticism and can withstand critique], the effect size being claimed is smaller than the margin of error on the tests.

Being a programmer, I know plenty of miserable, incompetent and outright criminal people with high IQs: the idea that IQ alone is something to maximize is just weird eugenics.

The impact of fluoride on actual social outcomes, measured by a double-blind study? That would be interesting. Maybe then we could talk about the ethics of inflicting life-long pain and suffering on children in favor of reducing their risk of unemployment by some small percentage.

What is being put forward right now, though, offers chem trail levels of rigor: it isn't going to be convincing to anyone who doesn't really, REALLY want to believe.

It doesn’t lower IQ. You need to read the actual linked article. Stop spreading lies.

> Why don’t schools teach toothbrushing? And/or have the school nurse check children’s teeth?

Some schools used to have a fluoride rinse students would be forced to do. It looks like it still happens in some rural places.

I had the swish at school, it was opt-in, not forced IIRC.

Edit add: I wonder if the swish is better overall as the fluid is spit out after rather than continuous ingestion?

It is less effective because it is spit out rather than ingested: https://www.researchgate.net/profile/Shou-Hua-Li/publication...

The most effective treatment was combining fluoride mouth wash and fluoride tablets.

I had fluoride treatment at the dentist instead city application. It was pleasant tasting and took minutes. You don't swallow it so is local only.

Anecdotal, but I am 40 and have never had a cavity. rarely floss and brush <2 times per day.

Oh the dreaded swish. I grew up in such a place.

We were taught toothbrushing in 1st grade, without follow ups or nurse checks.

> as long as we’re not collectivising the cost of dental caries

We certainly do, through ER visits and illnesses and medical events that can develop as a result of poor oral hygiene -- stroke and heart disease being among them.

Is that fair to the children that have to deal with the life long effects of bad teeth?

If in order to avoid a healthcare treatment, you have to avoid drinking or bathing or cooking with the public water supply, and also avoid most restaurant food, do you still have the right of informed consent to that treatment?

So do you avoid going outside to reduce exposure to environmental pollutants?

Water fluoridation is a net-benefit to society.

I don't think informed consent is violated by removing a pollutant. But adding a substance as a healthcare treatment denies informed consent as an individual right, and turns it into a majority right. I'd hate for that to happen to other civil rights.

Should we also stop adding iodide to salt or fortifying white bread? I see your point, but society has benefited as a whole by forcing some of these substances onto populations. I think it's fairly evident that many humans in the US are either unable or unwilling to really care about their health.

Bad analogy. Fortified food provide nutrients to supplement what you get from other foods. One can simply choose to buy white bread that's fortified, or whole foods that have those nutrients naturally.

You can't avoid water for too long though. Ingesting whatever is in the water supply is mandatory. I can't avoid flouride in my water any more than I can avoid Nitrogen when I breathe. I have no choice in the matter. It's the lack of choice that many object to, not the health effects of flouride per se.

Personally, if given the choice, I'd probably still take flouride. Having it in the water is convenient. Mandatory, but convenient.

Folks who don't want to drink flouride can use a reverse osmosis filter or drill a well.

You could also buy oxygen generators to avoid breathing as much nitrogen, but that's probably not a great idea in the long run.

It's also extreme individualism we've all been indoctrinated with and which is turned up to 11 in the US.

But uninformed consent to having you remove a necessary mineral from the water supply is fine?

If you are worried, you can get a gravity filter and take it out yourself.

> Water fluoridation is a net-benefit to society.

Banning more than one daily triple cheese burger would be net benefit to society as well. Likely more than we’re getting on dental cost savings. I doubt most would be okay with that though.

If you have strong evidence for your proposal, I haven't come across it in my literature reviews.

The only food I am aware of that has strong evidence that it contributes to poor health outcomes is sugary sodas. (The only other nutritional thing that consistently shows a negative impact on BMI is dieting: for everything else, populations are too heterogeneous for effects to be consistent. There are people whose combination of genetics + lifestyle make two or more triple cheese burgers a day a perfectly healthy diet.)

Outright bans and limitations on size of soda cups were both struck down by the courts, but soda taxes have been an effective public health intervention that reduce consumption and improve health outcomes: https://www.frontiersin.org/journals/public-health/articles/... And they do get widespread support among technocrats.

You could always move to a country which doesn't fluoridate their water supply.

But I am struggling to see how this has anything to do with a white paper highlighting and examining flaws in another white paper.

They don't even have to move to another country. They can move to parts of the United States that don't fluorinate or that don't have municipal water at all, or just get a gravity filter.

> fluorinate

Nitpick, fluorinated water, i.e. treating water with fluorine gas, produces hydrofluoric acid, oxygen and heat. Not tasty. Or keep your face on-y.

Fluoridated water matches up the fluorine atoms with a buddy who keeps them in check before introducing it to water. (Sort of like why you wouldn’t want to eat a chunk of sodium.)

Isn't it the case that countries that don't fluoridate only do so because their water sources already contain beneficial amounts?

i think the dissent in this thread is unqualified. Society is completely over "net-benefit" solutions. Stop perscribing 20th century one size fits all solutions. How about free flouride tablets instead of dosing everyone. Then saying "we need public policy to govern insurance rates". If this arugment saw its maxima, it would be manditory euthansia after 65. Certainly would really drop insurance rates. Btw genetics are a massive factor in oral hygine requirements, probably something your not considering. Should everyone wear the same brand/make of shoes?

Having to do work is different than getting adequate vitamins and minerals (which is all fluoride is) passively. It's no different than iodine in salt or vitamins B12, C and folic acid in cereal or vitamin D in milk.

We no longer go out and find the magic rock that we lick to ensure a good harvest or drink from the special stream that cures illnesses: we know what the human body needs to be able to do things like "grow teeth" and "not develop scurvy". Why would we go back to making people have to do a bunch of work to get access to basic nutrition? Because some weirdos want to take us back to a time when the average life expectancy in the United States was 40 years old?

The only point I put forth is that public fluoridation of water supplies doesn't infringe absolutely on an individual's right to informed consent to treatment since there is at least 1 method (moving) available that an individual can utilize to opt out. Others have pointed out that there may even be additional options available such as de-fluoridating yourself.

Did you have something on topic to contribute?

Or did you just want a soap box to voice your own opinions and I just happen to be collateral damage because you thought casting oblique aspersions about my qualifications would make you sound intelligent?

If in order to gain support for a political position, you have to publish fraudulent science; is the political position tenable?

Are you aware that fluoride is a natural mineral in all sources of water? People were found to have better teeth in areas with higher natural concentrations of the stuff. It's like yelling at the sun for administering vitamin D.

Informed consent for unnecessary medical treatment is just not a thing in the US. See also: infant circumcision.

That happens at the discretion of the parents, who are legal guardians and thus responsible for making informed decisions.

It is still a medical treatment added to the water supply, and sets a dangerous precedent. This same power if unchecked has the potential for great harm.

As for efficacy, the same (or greater) benefits to enamel hardness can be obtained from using fluoride toothpaste anyway, I do not see the urgency for this. They've stopped fluoridating their water in Scandinavia for years now.

> They've stopped fluoridating their water in Scandinavia for years now.

Note that Scandinavia has naturally high fluorine levels in their groundwater:

> In Sweden, fluoride concentrations in drinking water from water treatment plants have been reported to mostly range between 0 and 1.5 mg/L, with a maximum level of 4.1 mg/L, while in private wells in South-Eastern Sweden, it was found that 24% out of about 4,800 wells exceed 1.5 mg/L. In Norway, a study from 2017 found that 4 of 201 waterworks had fluoride concentrations exceeding guideline value of 1.5 mg F/L. In a study from Western Norway, the fluoride concentration in selected wells ranged from 0.51 to 8.0 mg F/L, and drinking water was the only dietary variable associated with increased risk of dental fluorosis. In Denmark, analyses of drinking water show most sources being low and below 1.5 mg F/L.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10770722/

The US targets 0.7 mg/L.

Many European countries also choose to add fluorine to milk and/or salt instead of water.

In no way does it set a dangerous precedent. Fortifying flour and iodizing salt (both of which could be termed a "medical treatment") were huge successes, with universally positive results and at virtually no cost. Mandating something like this should be done cautiously (in either direction), but fluoride isn't the first, only, or last example of it.

The only difference is that it's rather harder to avoid fluorinated water than iodized salt if one is so inclined, which raises the bar for proof of efficacy and preponderance evidence that it does not cause harm (which has been provided by others in this thread).

> It is still a medical treatment added to the water supply, and sets a dangerous precedent. This same power if unchecked has the potential for great harm.

Fluoridation started in US water supplies 80 (eighty) years ago. The people who set that "dangerous precendent" are all dead now. Seems like we've done OK with that "unchecked potential for great harm".

I mean, come on. Even as a libertarian argument this seems tone deaf in a month where we're literally rolling back the fourth amendment.

Very good point!

Fluor is an electron stealer. Enough for me not to touch it with a ten foot pole. Besides, tooth regrowing/regeneration will be available in the next few years.

> Fluoride, as an ion (F-), is not reactive in the same way that elemental fluorine (F2) is. Fluoride ions are stable and typically do not readily gain or lose electrons, while elemental fluorine is highly reactive due to its strong electronegativity and tendency to attract electrons from other elements.

As well as the cure for cancer

bad news about salt, then.

maybe they just don't want to deal with all the electronegativity

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