Higher levels of fluoride in pregnant woman linked to lower intelligence in their children

September 20, 2017 by Nicole Bodnar, University of Toronto
Fierce debate over the safety of water fluoridation – particularly for children’s developing brains – has fuelled researchers to explore the issue and provide evidence to inform national drinking water standards. Credit: Gullherme Jofill via Flickr

Fluoride in the urine of pregnant women shows a correlation with lower measures of intelligence in their children, according to University of Toronto researchers who conducted the first study of its kind and size to examine fluoride exposure and multiple states of neurodevelopment.

"Our study shows that the growing fetal nervous system may be adversely affected by higher levels of exposure," said Dr. Howard Hu, the study's principal investigator and professor of , epidemiology and global health at the Dalla Lana School of Public Health. "It also suggests that the prenatal nervous system may be more sensitive to fluoride compared to that of school-aged children."

Tap water and dental products have been fluoridated in communities in Canada and the United States (as well as milk and table salt in some other countries) by varying amounts for more than 60 years to prevent cavities and improve bone . In recent years, fierce debate over the safety of water fluoridation – particularly for children's developing brains – has fuelled researchers to explore the issue and provide evidence to inform national .

There are some known side effects of fluoride. For example, dental defects like mild staining are common among those ingesting recommended levels of fluoride in the United States and Canada. Skeletal fluorosis – excessive accumulation of fluoride in the bones – is much less common and only observed at levels of fluoride in the water that are more than five to 10 times higher than those recommended.

"Relatively little is known, with confidence, about fluoride's impact on neurodevelopment," said Hu, whose research team included experts from U of T, National Institute of Public Health of Mexico, University of Michigan, McGill University, Indiana University, Mount Sinai School of Medicine and Harvard School of Public Health.

The study, "Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico," published today in Environmental Health Perspectives, analyzed data from 287 mother-child pairs in Mexico City that were part of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project, which recruited pregnant women from 1994 to 2005 and has continued to follow the women and their children ever since.

The research team analyzed urine samples that had been taken from mothers during pregnancy and from their children between six and 12 years of age to reconstruct personal measures of fluoride exposure for both mother and child.

"This is significant because previous studies estimated exposures based on neighbourhood measurements of drinking water fluoride levels, which are indirect and much less precise measures of exposure. They also looked at children's exposures instead of prenatal exposures or had much smaller sample sizes of subjects to study," said Dr. Hu.

The researchers then analyzed how levels of fluoride in urine related to the children's verbal, perceptual-performance, quantitative, memory, and motor abilities at age four and once more between the ages of six and 12. Analyses were adjusted for other factors known to impact neurodevelopment, such as gestational age at birth, birthweight, birth order, sex, maternal marital status, smoking history, age at delivery, IQ, education, socioeconomic status and lead exposure.

With regard to the study's implications for populations in North America, researchers found that urinary fluoride levels in pregnant women were somewhat higher than, but within the general range of, urinary fluoride levels seen in non-pregnant general populations in Canada and the United States. However, in Dr. Hu's opinion, the findings do not provide enough information to suggest there is no safe level of fluoride .

"The potential risks associated with fluoride should be further studied, particularly among vulnerable populations such as and children, and more research on fluoride's impact on the developing brain is clearly needed."

Explore further: Pediatricians offer new dental recommendations

More information: Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico. Environ Health Perspect; DOI: 10.1289/EHP655

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11 comments

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nyscof
2.3 / 5 (3) Sep 20, 2017
We are all guinea pigs in this ongoing fluoridation experiment. Did you give your informed consent.

Fluoridation began in 1945 when entire populations were dosed with fluoride (eg Newburgh, NY; and Grand Rapids, MI) Political pressure forced acceptance before either study was completed. Long term health effects were never collected. Only school-age children were studied for limited short-term health effects (See: http://fluorideda...ent.html )

This new study adds to over 300 modern studies showing, not only that fluoride gets into the brain where it doesn't belong, but that fluoride is linked to neurological effects. Even the EPA acknowledges this. We will continue to be fodder for university studies to see just how much our brains can withstand before fluoridation is given up as the failed public health boondoggle that it is.
TopCat22
2.3 / 5 (3) Sep 20, 2017
So are we still getting fluoride in our drinking water in Canada and USA?

Why? and what purpose did it serve?

Certainly plenty of countries never did this to compare the effects...

Why is this not known and discussed more by the general public in today's internet era of information?

Why, by who, and how is it being covered up today? Whats the current justification and what was the original reason for it?

Shootist
5 / 5 (2) Sep 20, 2017
a double-blind study with 5 sigma results? Or just "correlation", as in, all people who drink milk as children die?
rrj500
5 / 5 (1) Sep 20, 2017
Nyscof, TopCat22 and other fluoridation opponents have apparently not read or understood the limitations of the studies they claim to reference. Like all other such studies used by fluoridation opponents in their attempt to prove drinking optimally fluoridated water causes serious health problems, this most recent one came up with a possible correlation – which is nowhere near proof of anything.

Like all other such studies, if you had actually read or understood the paper, you would have seen the lack of adjustment for the perhaps dozens of other possible risk factors which might influence IQ like lead, mercury or arsenic levels which were not available for most participants. Did you read the five paragraphs that described the rather significant limitations of their study? The author's conclusion was that their study might have demonstrated excessive levels of fluoride exposure "were associated with lower scores on tests of cognitive function". Proof of nothing.
Anonym
1 / 5 (2) Sep 20, 2017
:"Relatively little is known, with confidence, about fluoride's impact on neurodevelopment"

Nice to find this out now. What is known is that fluoride accumulates in the body over a lifetime of exposure. It makes bones harder (more brittle, too). It does nothing for the dental health of anyone, except kids whose tooth enamel is still hardening. To prevent caries in kids, we dose everyone with a potentially toxic, cumulative chemical closely akin to rat poison.
david_king
5 / 5 (1) Sep 20, 2017
With any luck we'll begin to understand how diet affects the gut biome which in turn affects carrie development. Meanwhile moving from a town with fluoride in the water to a town without, I suddenly developed 7 cavities as an adult in my thirties within a year of the move. Causal connection?
Chris_Reeve
Sep 20, 2017
This comment has been removed by a moderator.
manfredparticleboard
5 / 5 (2) Sep 20, 2017
Fluoride is in the drinking water of large populations around asia, tea accumulates the ion up to about 5 times the amount used in tap water amelioration when making a cuppa. The chemophobia that has driven the anti fluoride movement is not hinged to rationale. I grew up in a town without fluoride in the water and my nurse mother who knew the benefits, gave us kids fluoride tablets to chew occasionally. The difference between my family's teeth and our peers was quite distinct; which our family dentist was also willing to remark on. Big benefits small detriments, if any.
Chris_Reeve
Sep 20, 2017
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manfredparticleboard
5 / 5 (2) Sep 20, 2017

"So, regardless of the apparent beauty of your teeth, I think the matter is deeper than you've suggested here."

As far as the gut biome is concerned, it is such a complex and dynamic relationship between genes and diet that a single anion in low doses would not be of any great concern. Sugar and processed carbohydrates are of much greater negative influence on the gut biome and worrying about fluoride in low doses is about the same concern as sulphate or nitrate in you diet. Who's to say the state of my brain and functioning would be better if I weren't subjected to TV and advertising either...fluoride is a non event medically and socially.
Chris_Reeve
Sep 21, 2017
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