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

September 20, 2017 by Nicole Bodnar
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

Related Stories

Pediatricians offer new dental recommendations

August 25, 2014
(HealthDay)—All children should start using toothpaste with fluoride when their teeth appear, regardless of their risk level for cavities, according to new recommendations from the American Academy of Pediatrics (AAP).

US lowers recommended fluoride levels in drinking water (Update)

April 27, 2015
(HealthDay)—The U.S. government has decreased its recommended level of fluoride in drinking water for the first time in a half-century, to prevent staining of tooth enamel caused by overexposure to fluoride.

Hyperglycemia may cause caries but not periodontal disease

August 14, 2017
(HealthDay)—For rodents with diabetes, periodontal inflammation may be derived from dental caries rather than periodontal disease (PD), according to a study published online Aug. 9 in Diabetes.

Preventing tooth decay in children

April 14, 2017
Applying fluoride varnish to children's teeth is just as effective at preventing tooth decay as the alternative method of sealing teeth and could save the NHS money, concludes a study led by Cardiff University.

Fluoride in drinking water cuts tooth decay in adults

March 5, 2013
(Medical Xpress)—An international study conducted by researchers at the University of Adelaide has resulted in the strongest evidence yet that fluoride in drinking water provides dental health benefits to adults.

Recommended for you

Expert: Be concerned about how apps collect, share health data

October 20, 2017
As of 2016 there were more than 165,000 health and wellness apps available though the Apple App Store alone. According to Rice University medical media expert Kirsten Ostherr, the Food and Drug Administration (FDA) regulates ...

More teens than ever aren't getting enough sleep

October 19, 2017
If you're a young person who can't seem to get enough sleep, you're not alone: A new study led by San Diego State University Professor of Psychology Jean Twenge finds that adolescents today are sleeping fewer hours per night ...

Across Asia, liver cancer is linked to herbal remedies: study

October 18, 2017
Researchers have uncovered widespread evidence of a link between traditional Chinese herbal remedies and liver cancer across Asia, a study said Wednesday.

Eating better throughout adult years improves physical fitness in old age, suggests study

October 18, 2017
People who have a healthier diet throughout their adult lives are more likely to be stronger and fitter in older age than those who don't, according to a new study led by the University of Southampton.

Global calcium consumption appears low, especially in Asia

October 18, 2017
Daily calcium intake among adults appears to vary quite widely around the world in distinct regional patterns, according to a new systematic review of research data ahead of World Osteoporosis Day on Friday, Oct. 20.

New study: Nearly half of US medical care comes from emergency rooms

October 17, 2017
Nearly half of all US medical care is delivered by emergency departments, according to a new study by researchers at the University of Maryland School of Medicine (UMSOM). And in recent years, the percentage of care delivered ...

11 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

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
1 / 5 (1) Sep 20, 2017
Given the important nature of the topic, the large role that epigenetics plays at young ages, and the very believable mode of operation -- affecting the gut bacteria's complex ecosystem -- it's very difficult for me to relate to people who are so quick to reject the "fluoridation opponents".

If ever there was a topic to exhibit some caution about what we think we know, this is it. The researchers should very obviously continue to improve their studies in the light of what is at stake.
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
1 / 5 (1) Sep 20, 2017
Re: "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."

I don't know how old you are, but my understanding is that it is only in very recent decades that the link between gut bacteria health and proper brain functioning has become an established observation.

Who is to say what state your brain would be in without fluoride? You cannot tell us, unfortunately, and nobody can tell you.

So, regardless of the apparent beauty of your teeth, I think the matter is deeper than you've suggested here.
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
3 / 5 (2) Sep 21, 2017
Re: "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."

Don't you think you should distinguish adults from babies? Epigenetics has the most effect at the earlier ages.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.