3/29/2025 at 9:29:19 PM
I initially dismissed it as the same category of stupid as anti-vax beliefs, but it turns out that there are a decent amount of good studies showing a link between fluoride in water and (slightly) lower IQ when pregnant mothers ingest the fluoride. Note that there is no significant effect after birth.The idea is to remove fluoride from water and advise pregnant women to use fluoride-free toothpaste.
Everyone else can get enough fluoride from modern toothpastes, or regular dentist treatments.
The logic is that fluoride in tap water made sense in the era before toothpaste had it, but now it is “overmedicating” a vulnerable fraction of the population.
by jiggawatts
3/30/2025 at 12:54:24 AM
The IQ link is very heavily lacking in evidence.In the actual research the main "risk" posed by flouridated water is actually fluorosis. This causes minerals in your enamel to be replaced with flouride which can cause them to be brittle in the long term. It's pretty uncommon but the thought is that now that flouride toothpaste are commonplace, the benefit of flouridated water is also way less. Which changes the calculus.
A not insignificant number of researchers are advocating for the view that flouridating water just isn't worth it anymore and the (slight) risk of flourosis is more significant than the (slight) benefit of decreased dental caries.
by culi
3/30/2025 at 4:36:42 PM
Children are the main group that benefits from fluoride in water because the fluoride helps strengthen teeth as they form. Lack of fluoride increases childhood cavities, leading to decreased academic performance.This was a real problem in the San Jose school district until recently. They started fluoridation of water in the last ten years, and were the biggest US city that didn’t fluoridate. The evidence of the above is clear according to SJ dentists I have talked to.
by hedora
3/30/2025 at 4:47:15 PM
The National Toxicology Program recently completed a fairly substantial meta study and concluded that "for every 1 mg/L increase in urinary fluoride, there is a decrease of 1.63 IQ points in children.". [1] This is also relevant to OP since it's not just pregnant women at risk from excessive fluoridation but also children. For now it seems that adults are, somewhat oddly, unaffected.[1] - https://ntp.niehs.nih.gov/whatwestudy/assessments/noncancer/...
by somenameforme
3/30/2025 at 5:49:42 PM
In bold from your source:> It is important to note that there were insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies has a negative effect on children’s IQ.
by Aloisius
3/30/2025 at 6:50:28 PM
Yeah, note the measurement is in urine. So there are two separate issues. Determining whether fluoride is damaging to IQ, and then whether the levels in water can drive this. The former is way easier to evaluate than the latter. The reason comes from that study's intro pargraphs:---
"Since 1945, the use of fluoride has been a successful public health initiative for reducing dental cavities and improving general oral health of adults and children. There is a concern, however, that some pregnant women and children may be getting more fluoride than they need because they now get fluoride from many sources including treated public water, water-added foods and beverages, teas, toothpaste, floss, and mouthwash, and the combined total intake of fluoride may exceed safe amounts."
---
So the issue is trying to isolate the exact amount and source of fluoride people are getting. And that probably has no answer because it's going to vary dependent on how much fluoridated water somebody drinks, the rest of their diet, their other dental hygiene composition, and more. So levels that would be safe for one percent of the population, will be dangerous for another percent of it.
by somenameforme
4/1/2025 at 4:43:27 PM
Here is a concise detailed analysis of the concerns with the metaanalysis provided by the NTP:https://theunbiasedscipod.substack.com/p/the-well-runs-deep-...
The NTP report is flawed and likely biased.
by efirman
4/3/2025 at 3:34:30 AM
Says the substack paper which takes everything it can and spins and misrepresents it to the point of absurdity, for clicks.by somenameforme
3/30/2025 at 2:22:00 AM
Which changes the calculusWas that intentional? (https://en.wiktionary.org/wiki/dental_calculus for those who didn't get the reference.)
by userbinator
3/30/2025 at 2:44:39 AM
The canonical form is "I see what you did there".by kazinator
3/30/2025 at 6:07:29 AM
Fluorosis is very common afaik. My dentist told me I have it: slightly whiter patches on my teeth. Then he showed me his own fluorosis. It actually is stronger than the old enamel.by kjkjadksj
3/30/2025 at 1:22:09 PM
> The IQ link is very heavily lacking in evidence.Not really: https://jamanetwork.com/journals/jamapediatrics/fullarticle/...
by naasking
3/30/2025 at 2:33:22 PM
your study has been heavily criticized where you already posted it:https://news.ycombinator.com/item?id=43523900
I can only assume once you see those very valid criticisms, you will update your references
by shlant
3/30/2025 at 3:52:26 PM
Does the study not literally refute the claim that fluoride's negative impact on IQ is lacking in evidence, contrary to the original claim? What exactly do you think needs to be updated?by naasking