fluoridation – it pays to read carefully

I've spent a bit of time lately on the Making Sense of Fluoride Facebook page: I realise there's no convincing the committed anti-fluoride activists who spend time there, but like the other science-y people on the page, I'm hoping to provide information (& counter misinformation) for the 'lurkers' there: the people who visit & read but don't comment.

A common technique of those arguing against fluoridation on the MSF page is to dump large amounts of copypasta (from various sources) & tell us that if we'd only read it we'd see the rightness of their case. Or else, we get a lengthy list of references, & the same admonition. The problem is that if you pick a paper or two at random & do read it, you often find (as I've noted before) that it doesn't say what's claimed for it, or that it contains methodological errors that bring its findings into question.

For example (from a rather long list of references, all of which the commenter claimed to have read): a study by Reddy et al (2011) supposedly found that fluoride accumulated at very high levels in rats' brains. The researchers used 2 groups of male rats: one experimental group, one control. There were only 6 animals in each group, which is a very small sample size. The control group supposedly received no fluoride, but then there were no data on fluoride levels in the tap water they drank or the rat chow they ate. This is a significant flaw & I'd have thought it should have been picked up by peer review.

The experimental rats apparently received 20ppm fluoride by nasogastric tube for 2 months. Actually, it's not actually clear what dose they received: the abstract says 20ppm NaF, but the methods section says "20ppm concentration of fluoride". These are 2 different things. Either way the dose is about an order of magnitude higher than you'd find in fluoridated municipal water in New Zealand, in which case the paper didn't really support the commenter's assertions. Also, after those 2 months the researchers recorded 864mg/kg F- in the rats' brains: given that a large proportion of fluoride is normally excreted, and some of the rest fixed in apatites in bone, this figure looks extremely high & should surely have been questioned by the referees. 

And in addition, both groups of rats lost a great deal of weight during the course of the study. While the average body weight of the animals was 180g (+/-20g), after 2 months the control animals weighed on average 111g, while the experimental group was down to 93g (both +/- 2g). This strongly suggests they were either ill, or not receiving adequate food.

Another example: Bataineh & Nusier's 2006 report on the effects of sodium fluoride (NaF) on behaviour and reproduction in male rats is presented to us. Let's have a look: in the very first sentence of the abstract, we see that the experimental animals received either 100ppm or 300ppm NaF for 12 weeks, while the controls received normal drinking water (1.2ppm NaF). So the experimental rats were receiving a dose up to 2 orders of magnitude higher than what's normally found in fluoridated town supply! Unsurprisingly the control rats continued to do what rats normally do. In other words, the dose makes the poison – this paper does nothing to bolster claims that fluoridated municipal water is harmful to health. 

But point this out and what do we get? Cries of 'more excuses' and/or an immediate switch of attention to the next thing that appears to show teh ebils of fluoridation. It seems that the Gish Gallop is a technique not restricted to creationists.

Bataineh, H.N., Nusier, M.K. (2006) Impact of NaF on aggression, sexual behaviour and fertility in male rats. Fluoride 39(4): 293-301

Reddy, P.Y., Reddy, K.P., Kumar, K.P. (2011) Neurodegenerative changes in different regions of brain, spinal cord and sciatic nerve of rats treated with sodium fluoride. J.Med.Allied Sci 1(1): 30-35