Fluoride Free NZ’s (FFNZ) face book page is claiming:
Would you be interested to know that no studies have been conducted on fluoridated water at 0.7ppm to determine whether there is IQ reduction? The National Toxicology Program are currently completing research to fill this gap. You would have thought that they would have done this in the 1950s before starting the fluoridation program wouldn’t you?
There have actually been three recent studies from three different countries which have specifically investigated the claim of an effect of fluoridation on IQ – and, unsurprisingly, all threes studies showed there was no effect.
Here are those studies:
Broadbent, J. M., Thomson, W. M., Ramrakha, S., Moffitt, T. E., Zeng, J., Foster Page, L. A., & Poulton, R. (2014). Community Water Fluoridation and Intelligence: Prospective Study in New Zealand. American Journal of Public Health, 105(1), 72–76.
In fact, anti-fluoride activists in the US, as well as New Zealand, have campaigned against this study. Their major criticism is that the study also included the effect of fluoride tablet use. They argue that this makes the unfluoridated control group useless because many participants will have consumed fluoride tablets. However, they ignore the fact that the statistical analysis corrected for this but still found no statistically significant difference in IQ of children and adults from fluoridated and unfluoridated areas.
Other critics of the Broadbent et al. (2014) study have raised the issue of experimental power because of the numbers of people in the study. This could be a valid issue as it would determine the minimum effect size capable of being detected. Aggeborn & Öhman (2016) made that criticism of Broadbent et al., (2016) and all other fluoride-IQ studies. Their study is reported at:
Aggeborn L, Öhman M. (2016) The Effects of Fluoride in the Drinking Water. 2016.
Aggeborn & Öhman (2016) used much larger sample size than any of the other studies – over 81,000 observations compared with around 1000 or less for the commonly cited studies. It was also made on continually varying fluoride concentrations using the natural fluoride levels in Swedish drinking waters (the concentrations are similar to those in fluoridated communities), rather than the less effective approach of simply comparing two villages or fluoridated and unfluoridated regions. The confidence intervals were much smaller than those of other cited fluoride-IQ studies. This makes their conclusion that there was no effect of fluoride on cognitive measurements much more definitive. Incidentally, their study also indicated no effect of fluoride on the diagnosis of ADHD or muscular and skeleton diseases.
Another recent fluoridation-IQ study is that of Barbario (2016) made in Canada:
Barberio, AM. (2016). A Canadian Population-based Study of the Relationship between Fluoride Exposure and Indicators of Cognitive and Thyroid Functioning; Implications for Community Water Fluoridation. M. Sc. Thesis; Community Health Sciences, University of Calgary.
This study also had a large sample size – over 2,500 observations. This reported no statistically significant relationship of cognitive deficits to water fluoride.
Incidentally, Barberio (2016) also found there was no evidence of any relationship between fluoride exposure and thyroid functioning. That puts another pet claim of anti-fluoride campaigners to rest.
So much for NZFF’s claim that “no studies have been conducted on fluoridated water at 0.7ppm to determine whether there is IQ reduction.” But, just a minute, they are quoting the National Toxicology Program (NTP):
“No studies evaluated developmental exposure to fluoride at levels as low as 0.7 parts per million, the recommended level for community water fluoridation in the United States. Additional research is needed.”
But they omit the next sentence from the quote:
“NTP is conducting laboratory studies in rodents to fill data gaps identified in the systematic review of the animal studies.”
The NTP is discussing the research with animals, mainly rats, where effects of fluoride on the cognitive behaviour of the test animals have been reported but the fluoride concentrations are very high. And NTP’s assessment base on the review of the literature found only “a low to moderate level of evidence that the studies support adverse effects on learning and memory in animals exposed to fluoride in the diet or drinking water.” Hence the need for more research.
As part of the NTP’s research, which is currently underway, there are plans to extend studies to low fluoride concentrations more typical of that used in community water fluoridation.
The high concentrations used in animal studies is a major flaw in the anti-fluoride activist use of them to oppose community water fluoridation. For example, Mullinex et al (1965) (very commonly cited by anti-fluoride campaigners) fed test animals drinking water with up to 125 mg/L of fluoride (concentrations near 0.8 mg/L of fluoride are used in community water fluoridation).
While it is unlikely that the NTP research will find any significant effects of fluoride on the cognitive behaviour of rats at the low concentrations used in community water fluoridation the anti-fluoride campaigners have their fingers (and probably toes as well) crossed.
NTP will begin publishing the results of their new research next year (see Fluoride and IQ – another study coming up).