May 20 2014

New Study Shows Fluoride Safe

Public controversy over the safety of fluoridation programs continues, in some towns leading to successful resistance to water fluoridation. As a public health issue, the scientific evidence for risks vs benefits should be at the core of this debate. A new study sheds significant light on this question.

Some anti-fluoridation activists will latch onto any claim they feel supports their opposition (common behavior in any context), and this leads to a great deal of nonsensical conspiracy-mongering. My favorite is the claim that public water fluoridation is all a plot to allow companies to cheaply dump industrial waste into the public water supply.

These sorts of claims distract from the real issues, and in my opinion does a disservice to the anti-fluoridation movement. I don’t mind the existence of opposition movements, even if I disagree with their position. They can serve a useful function in driving public debate and keeping the powers that be honest and transparent.

When they utilize highly emotional but irrational arguments, however, they relegate their own movement to the crank fringe, they marginalize what might be legitimate issues, and they can lead segments of the public into making fear-based and ultimately harmful decisions. They also miss their opportunity to run an effective and ethical opposition which focuses on legitimate scientific issues, and to effectively advocate for the rights of individuals. (Again, I am not saying I agree with any particular such campaign – but at least focus on the real issues.)

Public water fluoridation programs are a proven safe and effective method to improve oral health. It should also be noted that such programs do not always add fluoride to water – they deliberately adjust the level of fluoride in the water supply to optimal levels. Sometimes this involves reducing fluoride levels, but often involves adding fluoride.

The new study involves the safety of such fluoride programs, and specifically addresses the question of whether or not there is an adverse effect on neurological development, as measured by standard IQ testing.

This issue was recently in the news following the infamous “Harvard study” that claimed to show an adverse effect from fluoride on IQ. I discussed the study here – which was really a systematic review and meta-analysis. In short, the researchers looked at studies that compared high vs low exposure to fluoride and measured IQ. They found that the high exposure group had a lower IQ compared to the low exposure group.

There are two main flaws with concluding from this study that fluoridations programs are not safe. The first is that the high fluoride exposure group (2-10 mg/L range) had exposures that were much higher than what is deliberately maintained in public fluoridation programs (0.5-1.0 mg/L range), which was considered the low fluoride exposure group in these studies.

In other words – the review really showed that the level of flouride in public water supplies with deliberate fluoridation is safe when compared to much higher levels of exposure.

The second major flaw was that the high exposure groups had exposure from toxic sources, such as burning coal, or from high natural sources of fluoride. These types of exposure potentially introduce many confounding factors, that were not controlled for.

The bottom line is that this review of studies provided no evidence that fluoridation programs are a risk to intellectual development, and if anything adds to the evidence for the safety of fluoridation programs (since that level of exposure was associated with a higher IQ).

The new study, unlike the studies in the Harvard review, is a study of exposure to fluoride through a public fluoridation program. This is an impressive study, in that it is a prospective study with a 38 year follow up involving over a thousand subjects with a 95.4% retention.

We conducted a prospective study of a general population sample of those born in Dunedin, New Zealand, between April 1, 1972, and March 30, 1973 (95.4% retention of cohort after 38 years of prospective follow-up). Residence in a CWF area, use of fluoride dentifrice and intake of 0.5-milligram fluoride tablets were assessed in early life (prior to age 5 years); we assessed IQ repeatedly between ages 7 to 13 years and at age 38 years.

The results were dead negative – no difference in IQ among any of the groups, regardless of fluoride exposure. There was a trend toward higher IQ in the fluoride exposed group, but this was not statistically significant, so the study was negative. The lack of correlation held up even when they corrected for possible confounders, like socioeconomic status.

This is as good as it gets for an observational study – a nicely controlled environment, large population, good long term follow up.


This latest study adds to the body of evidence showing that public fluoridation programs are safe, and specifically addresses the issue of IQ that was raised by the Harvard systematic review (which, to reiterate, wasn’t really relevant but was seized upon for anti-fluoridation propaganda).

For public controversies such as whether or not to adjust the level of fluoride in public water supplies, my wish is for the debate to be centered on and informed by the relevant science. If the question comes down to – what does the best scientific evidence say? Then that is something that can be objectively resolved.

Questions about ethics and the rights of individuals vs the duty of the state are more difficult to resolve objectively as there is a measure of personal value in the mix. That is where democracy comes in – we have to collectively decide what freedoms we will surrender in exchange for which public benefits.

But at least let the discussion be informed by proper science, and not obscured by pseudoscience, fear-mongering, and nonsense.

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