I think it's worth reminding people of Occam's Razor, and the point of it is: a simple explanation is often better than a complicated one. The US has had water fluoridation for 65 years, affecting 346 million people. That's a pretty big god damn sample size and long amount of time in which to observe effects. If we still have no proof of significant negative health effects, it's probably not bad for you . That said:…
Using a prospective Canadian birth cohort, we found that estimated maternal exposure to higher fluoride levels during pregnancy was associated with lower IQ scores in children. This association was supported by converging findings from 2 measures of fluoride exposure during pregnancy. A difference in MUFSG spanning the interquartile range for the entire sample (ie, 0.33 mg/L), which is roughly the difference in MUFSG concentration for pregnant women living in a fluoridated vs a nonfluoridated community, was associated with a 1.5-point IQ decrement among boys. An increment of 0.70 mg/L in MUFSG concentration was associated with a 3-point IQ decrement in boys; about half of the women living in a fluoridated community have a MUFSG equal to or greater than 0.70 mg/L. These results did not change appreciably after controlling for other key exposures such as lead, arsenic, and mercury.
To our knowledge, this study is the first to estimate fluoride exposure in a large birth cohort receiving optimally fluoridated water. These findings are consistent with that of a Mexican birth cohort study that reported a 6.3 decrement in IQ in preschool-aged children compared with a 4.5 decrement for boys in our study for every 1 mg/L of MUF.10 The findings of the current study are also concordant with ecologic studies that have shown an association between higher levels of fluoride exposure and lower intellectual abilities in children.7,8,26 Collectively, these findings support that fluoride exposure during pregnancy may be associated with neurocognitive deficits.
https://jamanetwork.com/journals/jamapediatrics/fullarticle/...