The MacDoctor was bemused to read that, in the face of opposed public opinion, Hamilton City Council are withdrawing fluoride supplementation from their town drinking water. Apparently they succumbed to the intense lobbying of people such as Mary Byrne of the Fluoride Action Network NZ, who makes statements like this:
“Fluoride is linked to many adverse health effects such as arthritis, thyroid dysfunction, lowered IQ and hypersensitivity.”
The MacDoctor begs to differ. He is relatively well-read and up to date in this matter and there is no reputable scientific study that demonstrates the above effects, merely some wishy-washy extrapolations of rat experiments and poorly controlled and executed epidemiological data. There appears to be some correlation between fluoride levels and hypertension, but it is by no means clear that this is a direct effect (it is likely fluoride levels in drinking water are a proxy for other, more important, factors). Increased fluoride levels may also increase rates of osteosarcoma (bone cancer), but studies are equivocal (i.e. some studies show a small increase, some show no increase).
About the only unequivocal negative effect of fluoride in the drinking water is fluorosis – whitened spots and patches on teeth caused by excessive ingestion of fluoride during childhood (especially under the age of 3). Currently it is thought ( and, so far, studies have born this out) that this complication is rare at the levels of fluoride optimal for prevention of dental caries (0.7mg/l). It can be avoided completely by not using fluorinated tap water below the age of 3. Breast milk and bottled water are completely safe in this regard.
Of course, none of this matters if fluorination of water does not prevent dental caries. Certainly Ms Byrne thinks this:
“The DHB could not produce any scientific evidence to prove fluoridation is safe, let alone effective.”
The MacDoctor loves the “prove it is safe” mantra loved by flakes the world over. Medicine (and dentistry) cannot prove that anything is “safe” – all interventions have side effects, some foreseen and some unanticipated. All one can demonstrate is that it has a benefit higher than any risks. And there one immediately sees the flakiness of people like Ms Byrne. She denies that fluorination of water prevents dental caries at all.
This is just silly. There is an ocean of evidence that fluoride in drinking water reduces the incidence of dental caries. Here is a link to just one recent Australian study involving 128 990 children. You can use the references at the end of the article to springboard to other confirmatory studies if you still need convincing. Note that the importance of this recent study is that it ably demonstrates that there is still a benefit to fluorination of water even in an age where tooth brushing with fluoride containing products is nationwide.
So, in summary, fluoridation of drinking water prevents tooth decay and has no proven downside apart from the purely cosmetic one of occasional fluorosis. The evidence for more substantial side-effects remains weak despite intensive ongoing investigation. As a preventative health measure it is considered one of the 10 most successful public health measures of the last century by the CDC. Only very silly people would ignore this.
And Hamilton City Council.