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Dunedin IQ-fluoride study Sloppy Science

Media Release

Fluoride Free New Zealand
(Fluoride Action Network NZ Inc)

20th May 2014

Dunedin IQ-fluoride study Sloppy Science

Not only were there too few unfluoridated children in this study to give reliable results (99), it is likely that they were a large proportion of the 139 children who took fluoride tablets. If so, there is no ‘unfluoridated’ group. Why was this not disclosed?

But worse, the study fails to allow for a whole range of confounding factors. The most important period for IQ damage is in the womb, yet the mothers’ fluoride intake and other factors like iodine deficiency were not controlled for. Similarly, there was poor information on total fluoride intake by these infants. Had the study actually been prospective as claimed, rather than retrospective, this essential information could have been available.

The Dunedin research report begins with the conclusion it set out to “prove” - that fluoridation is harmless. The first two named ‘researchers’ are two of NZ’s leading political promoters of fluoridation. They are dentists, not developmental neurotoxicologists.

In contrast, a Harvard University meta-analysis of studies was conducted by some of the world’s leading expert researchers into developmental neurotoxicology, who have no known bias on fluoridation policy. There were 27 studies reviewed. The total number now available is 43. The Dunedin authors wrongly dismiss this as a single study.

The Harvard review rightly caused concern to decision-makers as it showed a consistent lowering of IQ associated with fluoride intake. It is clearly the reason this Dunedin study has been published – as a political posturing, just as the tobacco companies funded and published ‘research’ showing cigarette smoking did not cause lung cancer.

The Dunedin IQ-fluoride study is missing just about all the confounding factors that the authors have criticised in the studies reviewed by the Harvard team. This is outright sloppy science. Broadbent criticizes the studies reviewed by Harvard for not controlling for these factors (when in fact some of them did) and then fails to control for them when the data is readily available to him.

This is a single ‘study’ by politically driven dentists against a robust analysis of 27 studies by world-leading experts in this field, from one of the world’s foremost universities. You’d have to have a pretty low IQ to not know whose opinion carries the more credible weight.



July 25, 2012 — For years health experts have been unable to agree on whether fluoride in the drinking water may be toxic to the developing human brain. Extremely high levels of fluoride are known to cause neurotoxicity in adults, and negative impacts on memory and learning have been reported in rodent studies, but little is known about the substance’s impact on children’s neurodevelopment. In a meta-analysis, researchers from Harvard School of Public Health (HSPH) and China Medical University in Shenyang for the first time combined 27 studies and found strong indications that fluoride may adversely affect cognitive development in children. Based on the findings, the authors say that this risk should not be ignored, and that more research on fluoride’s impact on the developing brain is warranted.

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