Regarding long-term effects of flouride, the national academy of sciences (NAS) has a report from 2006 which gives a comprehensive interpretation of the scientific literature. The NAS was tasked by the EPA with doing the review to evaluate safety of flouride supplementation of drinking water.
The report costs $50-$80 (on-line versus print).
For adults concerned about taking flouride supplements (like me), the report is inconclusive. Here is a summary as I understand it.
My recommended dose is about 10mg flouride (3 florical tablets) daily. The report recommends that the daily dose in water should not exceed about 1-2mg/liter (giving a typical person a maximum flouride dose of 2-3mg daily). Above 4mg/liter the report warns of adverse health consequences (summarized below).
The adverse health consequences discussed are mostly for developing kids or for people exposed to 4mg/L or more for decades. Most people considering flouride supplements are not in this category. So the report is not conclusive regarding supplements. Still, after reading the report, I am pretty sure I don’t want to take 10mg flouride per day for an extended period. A year makes me a little nervous.
The kinds of problems discussed in the report are:
- bones, muscles, teeth
- reproduction and development
- neurotoxicity (brain) and behavior
- endocrine (hormones)
The studies cited by the report are only suggestive, not conclusive. Existing studies done on humans are only epidemiological (studying population data, not doing experiments), and these seem to focus on children. The remaining studies are mainly on rats. These studies seem to show clear biological effects on bones and brains (and perhaps other organs, I didn’t read the full report) at daily dosages less than the rat-equivalent of 10mg. Whether these effects cause health problems is unclear.
Furthermore, the risks seem complicated. For example, some of the problems show up only if low levels of aluminum are also in the diet, and the level of aluminum matters – higher levels, or very low levels, lower the risk.
My summary conclusion is that there are probably some risks of taking 10mg/day flouride, although the degree of risk is not clear.