Hold Your Water!?!

“Look, Ma! No cavities!” Toothpaste makers have patted themselves on the back for keeping kids cavity free for decades, but adding fluoride to public drinking water for dental purposes, which began in 1945, has also played a big role in oral health. The practice has had plenty of detractors, and the latest research may have consumers rethinking their brushing and drinking habits.


A new study suggests that prenatal exposure to this chemical may affect cognitive abilities and that children born to mothers exposed to high amounts of fluoride could have lower IQs.
The study, published last week in Environmental Health Perspectives, found an association between lower intelligence and prenatal fluoride exposure in 299 mother-child pairs in Mexico. The team measured fluoride levels from mothers via urine samples and followed up on their children until they were between 6 and 12 years old. Even when other possible factors were taken into account, such as exposure to other chemicals, results continually showed that higher prenatal fluoride exposure was linked to lower scores on tests of cognitive function in children at age 4 and then again between 6 and 12.
 

Although the study accurately measured how much fluoride was in each mother's urine samples, it could not pin down the exact amount of fluoride the children had been exposed to. That's because pregnancy can change how certain substances are secreted in urine. However, the team estimates that these levels of exposure are not exceptionally high.


“If you just assume for the moment that fluoride in the urine of pregnant women is the same as it is in nonpregnant women, then these levels are a bit higher—but not hugely higher—than that seen in general population samples in North America,” lead study author Dr. Howard Hu, who studies environmental health at the University of Toronto, tells Newsweek. 


The mothers in this study did not have fluoride added to their water. Rather, they ingested fluoride from natural sources or through fluoridated salt and supplements. In Mexico, fluoridated salt is the main way that women get salt into their diet, says Hu, unlike in the US, where fluoridated water is the main avenue.


The data could renew the debate about the safety of adding fluoride to tap water, in part because experts have not been quick to dismiss the findings. And yet, the benefits of fluoride are well documented.


Fluoride is a naturally occurring chemical that is noted for its ability to help prevent tooth decay and is often added to public drinking water for this reason. According to the Centers for Disease Control and Prevention, drinking fluoridated water reduces cavity occurrence by 25% in areas where it is practiced. In 2014, about 74% of the US population was on fluoridated public water systems, and by 2020 the CDC hopes to increase this number to 79.6%.  A large body of research has confirmed the safety of fluoride in water. One review of more than 70 studies concluded that the practice was safe. A 2009 review of more than 50 studies deemed the practice safe. A study in 1996 called the evidence confirming the safety of water fluoridation “compelling.”


And yet, at least one pediatrician is taking a closer look at fluoride's role in human health


“This is a very well-conducted study, and it raises serious concerns about fluoride supplementation in water,” says Dr. Leonardo Trasande, a pediatrician who studies potential links between environmental exposures and health problems at New York University Langone Health. (He was not involved in the new study.)


Trasande emphasizes that the levels of fluoride seen among the mothers in this study are slightly higher than what would be expected in US, based on current fluoride supplementation levels. However, he also explains that fluoride is known to disrupt thyroid function, which in turn is crucial for brain development.


“These new insights raise concerns that the prenatal period may be highly vulnerable and may require additional reconsideration,” Trasande says.