Fluoride and Intelligence

Dr. Ken Walker, more well known under his pseudonym, W. Gifford-Jones, has a column published by 70 Canadian newspapers, several papers in the U.S., and the Epoch Times which has editions in a number of European countries. Because of his notoriety, he can be quite influential in shaping public opinion of medical and health issues. Most of the time, his columns are quite informative and helpful. Sometimes, however, he takes sides on issues where he is at odds with the best available medical  information. In extreme cases he moves into conspiracy theory territory.

Recently, he tackled water fluoridation using the familiar conspiracy theorist tactics of scaremongering and dis-information. This particular article, available at C-Health on the Canoe Network, has a title designed to strike fear into any parent’s heart: “Water fluoridation may affect children’s IQ”.  To set the stage, his opening paragraph is even more terrifying than the title.

Why, in 1974, didn’t authorities learn from this terrible tragedy? A 3-year-old Brooklyn boy, during his first dental checkup, had fluoride paste applied to his teeth. He was then handed a glass of water, but the hygienist failed to inform him to swish the solution around in his mouth and then spit it out. Instead, the boy drank the water and, a few hours later, he was dead from fluoride poisoning. A report in Clinical Toxicology of Commercial Products calls fluoride an acute toxin with a rating higher than lead.

Although hundreds of millions of people have been treated with fluoride, he reports a single incident that happened almost 40 years ago. There may be others, but if Gifford-Jones has to go back that long for such an instance, we can assume that you, or your children, are more likely to die from Bubonic Plague, than from fluoride overdose, at least if you live in the United States.

Gifford-Jones then moves on to a study written by researchers at the Harvard School of Public Health (HSPH) and published in the Environmental Health Perspectives  that links fluoride consumption in childhood with decreased mental acuity later in life. However, in his discussion of the paper, he moves from scare tactics to outright misrepresentation of the intent and the content of the paper.

The study looks at children from two communities located close to each other. Researchers discovered that children in the low-fluoride area had a 28% chance of being normal, bright or of high intelligence. In the high-fluoride area the figure was 8%. Researchers also found that, in the low-fluoride community, 6% of children suffered from mental retardation compared to 15% in the high fluoride community.
The HSPH says that there are now 23 human and 100 animal studies that link the use of fluoridated water to brain damage. These findings show an increase of aluminum and beta amyloid plaque in the brain, both of which are associated with Alzheimer’s disease. Researchers have also noted a decrease in acetylcholine receptors, which help to transmit nerve messages. These changes could have an adverse effect on a child’s neurological development.

The paper itself does not use the phrase “Mental retardation”, so I am unsure where Gifford-Jones gets his numbers. From Medline, we learn that the average rate of mental retardation in the US is 1-3% of the populations so the first question we must ask is why are his number so extremes. He suggests that in high-fluoride areas that 92% of the population is below average intelligence. Even in the low-fluoride areas, 72% are below average. There is something very wrong here, and I suggest that Gifford-Jones is at the base of it.

The abstract of the paper, written by  Choi AL, Sun G, Zhang Y, and Grandjean P. of (HSPH) seems very intimidating:

Background: Although fluoride may cause neurotoxicity in animal models and acute fluoride poisoning causes neurotoxicity in adults, very little is known of its effects on children’s neurodevelopment. Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development. Methods: We searched the MEDLINE, EMBASE, Water Resources Abstracts, and TOXNET databases through 2011 for eligible studies. We also searched the China National Knowledge Infrastructure (CNKI) database, as many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, endpoints of IQ scores or related cognitive function measures with means and variances for the two exposure groups. We estimated the standardized mean difference (SMD) between exposed and reference groups across all studies using random effects models. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking water fluoride as the only exposure. Cochran test for heterogeneity between studies, Begg’s funnel plot and Egger test to assess publication bias were performed. Meta-regressions to explore sources of variation in mean differences among the studies were conducted. Results: The standardized weighted mean difference in IQ score between exposed and reference populations was -0.45 (95% CI -0.56 to -0.35) using a random-effects model. Thus, children in high fluoride areas had significantly lower IQ scores than those who lived in low fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease. Conclusions: The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.*

However, when we examine the paper (pdf) itself, we discover that the researchers are actually looking at studies from China where naturally occurring fluoride levels are as much as an order of magnitude higher than the levels added to North American community water systems. Acceptable levels of fluoride in drinking water in Canada and the US range from 0.7mg/L to 1.2mg/L, with the lower end considered optimal. The levels in some of the Chinese communities in the study were as high as 11.5mg/L; all of the communities selected as having high levels fluoride concentrations were well in excess of Health Canada and CDC standards.

Even with such large fluoride concentrations, the authors were very careful about what conclusions could be drawn from their analysis. For example:

  • Information on the child’s gender and parental education were not reported in more than 80% of the studies, and only 7% of the studies reported household income. These variables were therefore not included in the models. These two factors alone can account for differences in intelligence tests.
  • Although fluoride exposure  showed inverse associations with test scores, and dose-related differences in test scores occurred at a wide range of water-fluoride concentrations, the available exposure information did not allow a formal dose-response analysis.
  • The estimated decrease in average IQ associated with fluoride exposure based on our analysis may seem small and may be within the measurement error of IQ testing.

As in any meta-analysis, two of the possible confounding factors can be the inclusion criteria and the cross-study statistical analysis. Both of these are beyond my ability to tackles with any degree of certainty, so I will assume the authors acted appropriately.

Leaving this study behind for now, Gifford-Jones moves to another area of concern, albeit less terrifying than death or lowered intelligence—dental fluorosis.

Most parents are not aware of dental fluorosis, a discolouring of teeth due to excess fluoride that can occur in children between the ages of three months and eight years. In 1940 this mottling of teeth occurred in 10% of children. Today, in some areas, it’s as high as 55%. One possible reason for the increase is that children’s toothpaste tastes good and they swallow too much of it.

Some simple numbers with no references. Are they accurate? Is it important? More importantly, after his misleading take on the Harvard study, should we believe him? Let’s see what Health Canada has to say on dental and skeletal fluorosis.

Dental fluorosis is the most widely and frequently studied of all adverse effects of fluoride. It is the effect occurring at the lowest level of fluoride exposure in the population. Mild and very mild dental fluorosis are not considered to be adverse effects, whereas moderate dental fluorosis is found to be an adverse effect, based on its potential cosmetic concern, and is used as the endpoint of concern in the risk assessment used to establish the Maximum Acceptable Concentration. By protecting against a cosmetic effect of moderate dental fluorosis, Canadians are also protected against the adverse health effects of severe dental fluorosis.

Skeletal fluorosis is the most serious adverse health effect clearly associated with prolonged exposure to high levels of fluoride in drinking water. Skeletal fluorosis can occur at very high exposure levels, and has rarely been documented in Canada.

Far from ignoring any issues with fluoride, Health Canada has recommendations for dealing with groundwater with naturally high levels of fluoride. I guess Health Canada must be in the pocket of Big Fluoride.

Now for some irony.

I believe it’s dangerous for health authorities to brush aside the Harvard study. So-called experts are not always right. As noted astronomer Carl Sagan once remarked, “Arguments from authorities do not count. Too many authorities have been mistaken too often.” I say amen to that.

In other words “Don’t pay attention to other authorities, just me”

And for the grand finale, back to the top:

This is just my opinion about fluoridation and, since I’m not related to the Almighty, I could be wrong. But it appears that since the 3-year-old boy died, experts have continued to ignore the dangers.

Gifford-Jones gives us a masterful example of how to influence public opinion with a combination of scare tactics and misinformation that borders on outright lies. Despite the impression  he leaves, both the CDC and Health Canada continually monitor research on fluoride exposure and pay attention to the scientists not the scaremongers.

I echo his final comments, but rather than comparing myself to a deity, I’ll say simply that I am not a toxicologist, and I could be wrong.

For more on Fluoride, see Steve Thoms’ article from 2010.


7 Responses to “Fluoride and Intelligence”

  1. Paul says:

    The other detail he fails to mention is the fact that the “low fluoride” areas had fluoride levels approximately equal to fluoride levels in fluoridated municipal water supplies in North America. “Dr. W. Gifford-Jones” makes me crazy.

  2. I remember reading “W Gifford-Jones” way back in the last century, I think in the Ottawa Citizen. My recollection of his articles is that they generally did a good job of explaining standard medicine to the lay public. I was therefore astonished and disappointed to see reading some of his recent stuff that he appears to now be a follower of pseudoscience and woo.

  3. Good article, especially for dealing with fluoride scaremongering. Hearing that stuff drives me nuts, especially because I don’t have the research or scientific knowledge to firmly refute it on the spot. I’m glad I found a science-based blog.

  4. Erik Davis says:

    Note that the authors have disavowed the applicability of their research to the US water fluoridation debate:


    Predictably, those fighting fluoridation remain unconvinced.


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    John Underhay, also known as Peicurmudgeon, is just your average atheist, left leaning, SCUBA diving, snorkeling, biker. He lives on PEI and spends some of his time attempting to point out the flaws and or dangers in promoting ideas that run contrary to the laws of physics, chemistry, or biology. He has a BSc (Biology) and an MSc (Pharmacology) from the University of Prince Edward Island, and is currently retired. You can read more of his posts at http://peicurmudgeon.wordpress.com/