| Celia Ford is a Future Perfect Fellow focusing on the intersection of emerging technology, culture, and the mind. |
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| Celia Ford is a Future Perfect Fellow focusing on the intersection of emerging technology, culture, and the mind. |
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Could fluoride lower IQ in kids? The debate, explained |
If you live in the US, there’s a good chance you’re one of the approximately 209 million people drinking tap water that contains added fluoride. Local governments have been putting fluoride in city water supplies for nearly 80 years.
In many ways, its addition has been a remarkable public health success: According to the Centers for Disease Control and Prevention (CDC), drinking fluoridated water reduces tooth decay by 25 percent. But in late August, the US National Toxicology Program (NTP) published a long-awaited report declaring, with “moderate confidence,” that drinking water with elevated fluoride levels is linked to lower IQ in children.
Fluoride in our drinking water has inspired conspiracy theories for generations. Robert F. Kennedy Jr., who is also a prominent anti-vaxxer and Covid-19 skeptic, is one of the most vocal proponents of banning fluoridation to protect children from neurodevelopmental problems.
This, though, isn’t a conspiracy theory. Scientists have spent decades trying to figure out what level of fluoride strikes the best balance between oral health and healthy brain development. The NTP’s new 324-page report reviews results from over 500 experiments, lending more weight to the idea that fluoride can be connected to brain problems than, say, a single fraudulent, now-retracted study linking vaccines to autism.
Science is a frustratingly non-linear process. Facts that seemed unquestionable a decade ago can be overturned by new data at any moment. If you’ve never thought about fluoride outside of the dentist’s office, hearing that it might have neurotoxic effects could be confusing, scary, or infuriating. Why is fluoride still in our water and toothpaste, then?
It’s not because dentists and scientists are lying to us (although sometimes they do). It’s because finding the whole, unshakable truth is a never-ending process. So, don’t throw out your toothpaste and stockpile bottled water just yet. Here’s what the science says (and doesn’t say) about fluoride and the brain. |
Why does the government want us to drink fluoride? |
Fluoride is a mineral found naturally in soil, water, and things we consume, like brewed tea and shellfish. It’s also in the toothpaste most of us use. Fluoride strengthens our enamel and prevents cavities. It’s about more than maintaining pearly white teeth; left untreated, tooth decay leads to severe infection, which can spread throughout the entire body.
At the turn of the 20th century, dental researchers noticed that many people living near high-fluoride water sources had splotches on their teeth, a condition called fluorosis. Once scientists began studying the effects of fluoride on dental health, they realized that, while fluoride can damage teeth and bones at high concentrations, drinking water with low levels of fluoride actually prevents tooth decay. Today, many cities add a small amount of fluoride to their tap water — about 0.7 milligrams per liter (mg/L).
But around 1.9 million people in the US live in areas where tap water naturally contains more fluoride than the government recommends, according to the report. For example, the Ogallala Aquifer, which provides water for West Texas, is infused with fluoride-rich volcanic ash, bringing its fluoride concentrations up to a whopping 5 mg/L.
The report linked fluoride levels of 1.5 mg/L — about twice the level recommended by federal health officials — with lower IQ in children. According to the NTP, more research is needed to figure out whether there are also risks associated with higher levels of fluoride for adults, or with the lower concentrations the government recommends.
While these findings have been reproduced enough times to be worth taking seriously, the science of intelligence — including the concept of IQ itself — is questionable. |
Measuring brain development is complicated |
Thomas Trutschel/Photothek |
Measuring brain function isn’t straightforward. After all, the brain has many functions: keeping the body alive, helping us walk and talk, guiding our learning and decision-making.
More than 70 of the 100 human studies reviewed by the NTP specifically looked at children’s IQ as a proxy for brain development — IQ tests are easier and cheaper to run than, say, brain scans or full neurological exams. Of those 72 IQ-related studies, only 19 were flagged by the NTP as having a low risk of bias, controlling for factors like socioeconomic status, which could also contribute to differences in IQ scores. Only a handful of those 19 studies were conducted in North America, and none in the US.
So, critically, none of these human studies tell us anything about how fluoride changes the brain at a biological level. Even studies in lab animals and cells did not identify how fluoride might affect learning, memory, or intelligence.
IQ scores also only capture an incomplete picture of early childhood brain development and are tangled up in a number of socioeconomic, racial, and cultural factors beyond how much fluoride someone is exposed to.
Historically, mothers were blamed for their children’s cognitive disabilities. Redirecting that blame to environmental factors like MMR vaccines — or, say, fluoridated water — can give parents a sense of control over scary-sounding diagnoses. A 2017 federal lawsuit calling on the EPA to ban water fluoridation already has the enthusiastic support of high-profile anti-vaxxers.
The trial hinges on the results of NTP’s final report, a draft of which was originally presented over a year ago. The drawn-out legal battle has been messy, with dental health advocates obstructing fluoride research and denying the NTP’s findings.
If the court decides fluoride poses health risks that outweigh its benefits, it could end water fluoridation in the US.
Amid scientific uncertainty and political shadiness, it’s hard to know what to believe. |
So, who should I believe? And what should I do? |
For now, the NTP has simply determined “with moderate confidence” that there is a correlation between higher fluoride exposure and lower IQ in children — specifically, IQs 2 to 5 points lower.
But it’s hard to know how we would measure the differences in lived experiences based on a few IQ points.
If you’re concerned about your family’s fluoride exposure, you can check your tap water’s fluoride levels on the CDC’s My Water’s Fluoride page. If you happen to live somewhere with levels above around 1.5 mg/L, your tap water crosses the threshold of neurodevelopmental concern. No need to switch to bottled water, though; home water purifiers can filter fluoride out completely.
To make sure you don’t throw out the oral health benefits of fluoride with the bathwater, keep using fluoride toothpaste for those over the age of 2 (just don’t swallow it).
And if you’re still fluoride-skeptical, you can order some hydroxyapatite toothpaste — which has similar cavity-preventive benefits — from Europe or Canada, where it’s been approved and endorsed by dental associations. |
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| The migrant crisis, via Chicago |
Around 50,000 migrants have poured into Chicago in the last two years. Some Chicagoans are furious. We talk to residents, clergy, and migrants on Chicago's South Side about an issue that may be Kamala Harris's biggest liability. |
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Catch up on The Rings of Power lore: The second season of The Rings of Power has premiered on Amazon. We’ve got a refresher on everything that happens in Middle-earth’s Second Age, which occurs thousands of years before the events of The Hobbit and The Lord of the Rings.
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Taylor’s bestie faces backlash: Brittany Mahomes, the wife of Kansas City Chiefs quarterback Patrick Mahomes, is in hot water for liking pro-Trump content on social media. While the political views of a sports WAG don’t usually captivate the public, Mahomes’s close friendship with pop star Taylor Swift has drawn more scrutiny of her online activity.
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Harris’s big housing plan has a big problem: Democratic presidential nominee Kamala Harris has two incompatible goals — to make housing more affordable for Americans, and to help more Americans build wealth through real estate investments. Her plan aims to reduce housing costs through construction and tax incentives, but doing so would make real estate a less valuable investment for owners.
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“We’ve opened the door to political violence”: Legal scholars, national security experts, law enforcement, and gun violence researchers are watching closely this election season to monitor potential threats, and while experts aren’t anticipating large-scale violence, they can’t rule out the possibility of sporadic outbreaks and outliers.
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AI isn’t being “shoved down your throat”: The AI boom has been met with enthusiasm and resentment from users and researchers alike. Whether you’re a skeptic or an optimist, it helps to remember that the technology is in its infancy — and working out the kinks with adjustments and oversight will make a better experience for everyone.
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Hotdogs, hotdogs, get your hotdogs here: And everything else. One-third of American consumers now shop at Costco. The big-box retailer has figured out how to appeal to consumers in the United States, who love its aspirational ethos coupled with its significant value proposition. [New York Times]
Slow your roll: In 2022, the government reported that the average amount of THC in weed had more than tripled versus cannabis from 25 years ago. While legalization has created better access to weed, the high tolerance of regular users has driven the industry’s incline toward high-potency cannabis that can be dangerous for young and inexperienced users. [The Atlantic]
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Photo illustration by Mario Tama/Getty Images News |
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Keep an eye out for Katseye |
Netflix’s Pop Star Academy: Katseye asks and answers the very simple question: Can you create the next big K-pop sensation from scratch? The series is a glimpse into the making of the girl group known as Katseye, a collaboration between Korean entertainment company HYBE and American label Geffen Records. They've invited 20 talented girls from around the world to sing and dance for their lives in a year-long training program that doubles as an audition. Each month, the girls are mercilessly evaluated (down to how they position their pinky fingers during a dance move) and risk getting cut.
One might think that the competition itself would be a cutthroat, every-girl-for-themselves, Hunger Games-style situation, but what the girls and the audience watching at home find out is that no one’s as ruthless as the executives — who play mind games, give brutal evaluations, and pit the girls against one other — as they call all the shots.
—Senior correspondent Alex Abad-Santos |
Christopher Polk / Billboard |
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Today’s edition was produced and edited by senior editor Lavanya Ramanathan, with contributions from staff editor Melinda Fakuade. We'll see you tomorrow! |
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