An evidence-based discussion of the Canadian fluoride/IQ study

Dr. Christopher Labos and Jonathan Jarry discuss the recent Canadian fluoride/IQ research. They provide an expert analysis of the paper and its problems. Click on image to go to podcast.

The critical debate about the recent Candian fluoride/IQ study is continuing. Dr. Christopher Labos and Jonathan Jarry of The Body Of Evidence group discussed the research in their recent Podcast. The subject is appropriate because, as their website says:

“The Internet allows fantasies to thrive, but your health (and wallet) should not be the target of nonsense. There is a body of evidence out there, and Dr. Christopher Labos and Jonathan Jarry are staring it right in the face.

Through a podcast, a shared blog, and videos (and even appearances on the radio and in person), they explore what reproducible evidence has to say on important medical topics, and how scientific thinking shouldn’t be the sole purview of researchers. The bickering is just the cherry on top.”

The discussion is in Podcast 053 – Smart Drugs and Fluoride. The section on the Canadian fluoride/IQ study starts at 30 minutes and is 10 minutes long.

It’s a very thorough discussion going into a range of problems with these sort of studies and problems with the particular study. It raises the issue of differing results obtained by similar studies (eg the Mexican study did not report differences between boys and girls although the Canadian study did see Paul Connett’s misrepresentation of maternal F exposure study debunked and other articles here). They also discuss important factors the Canadian study ignored

Clearly, there is a lot wrong with the Canadian study – or at least a lot of factors that a sensible reader should take into account.

An important issue is the ethics of publishing controversial studies like this. In particular, the authors should have been aware that their results would be used by anti-fluoride activists to scaremonger in their campaign against community water fluoridation (that is certainly happening in New Zealand). And the most effective scaremongering is raising fears about children. Christopher and Jonathan suggest that in such a situation the authors should have been responsible enough to do further work to eliminate doubts or at least present their findings in a more qualified way. The authors should have been more diligent considering the way their findings were going to be used by activists.

The fact that this was not done suggests to me that other factors, such as professional ambition and pressure form immediate peers and their institution came into play (see Politics of science – making a silk purse out of a sow’s ear).

They also finish with a discussion of the nature of IQ tests and suggest that the differences claimed by the researchers are rather meaningless given that the average IQ of the children in the study were above average.

There is a very strong message here for the non-specialist. In cases like this, one should never simply accept the initial claims because they can be highly motivated. Christopher and Jonathan recommend that non-specialists should wait several days for the more balanced views to be published. There are plenty of experts out there who can provide this balance – they just have to be given time to actually read the paper, work out what the data means and how that compares with the claims made by authors.

For other comments on the Candian fluoride/IQ research see:

• If at first you don’t succeed . . . statistical manipulation might help
• Politics of science – making a silk purse out of a sow’s ear
• More expert comments on the Canadian fluoride-IQ paper

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