What a new study does — and doesn't — say about fluoride and its link to IQ

A caller report linking fluoridated drinking h2o to little IQ scores successful children is definite to ratchet up the statement implicit a signifier that’s considered 1 of the greatest nationalist wellness achievements of the 20th century.

The study published Monday successful JAMA Pediatrics synthesizes the results of dozens of probe studies that person been released since 1989. Its wide decision is that the much fluoride a kid is exposed to, the little helium oregon she tends to people connected quality tests.

The investigation was conducted for the U.S. National Toxicology Program, and it has attracted a bully woody of disapproval implicit the galore years of its development. Among the biggest critiques is that it’s based connected information from places wherever fluoride levels are acold higher than the attraction recommended by the U.S. Public Health Service.

Adding fluoride to assemblage drinking h2o is credited with reducing the mean fig of teeth with cavities by 44% successful adults and 58% successful adolescents since the 1960s, the wellness work says. Yet adjacent with the proliferation of fluoride-containing toothpastes and dental sealants, bony decay is inactive the most communal chronic disease affecting American children, and the mean elder national is missing at slightest 10 imperishable teeth.

About 209 cardinal Americans person fluoridated h2o successful their taps, according to the Centers for Disease Control and Prevention. Robert F. Kennedy Jr., President-elect Donald Trump’s pick to pb the Department of Health and Human Services, has said he’d similar to spot that fig fall to zero, successful portion owed to concerns implicit “IQ loss.”

The JAMA Pediatrics study is based connected enactment prepared for the National Toxicology Program’s 324-page monograph connected fluoride and encephalon development, which was finalized successful August. Here’s a person look astatine what it does — and doesn’t — show.

Where bash the information travel from?

The study combines information from 74 studies connected fluoride vulnerability and children’s IQ. The bulk of them — 45 — were conducted successful China, and different 12 were from India. None were from the United States, though 3 were from Canada and 4 were from Mexico.

Ten of the studies were designed to follow groups of radical implicit time to spot however their differing levels of fluoride vulnerability affected IQ scores and different outcomes. The remainder of the studies assessed a population’s fluoride vulnerability and IQ at the aforesaid time.

IQ scores were usually reported arsenic averages for a group, though sometimes they reflected an individual’s circumstantial level of fluoride exposure.

How overmuch fluoride are we talking about?

Fluoride vulnerability was measured aggregate ways.

Sometimes researchers measured the magnitude of fluoride successful a community’s drinking water, and sometimes they measured the magnitude of fluoride successful participants’ urine. Dental fluorosis — a information that occurs erstwhile teeth get excessively overmuch fluoride and look to beryllium stained — was besides utilized to measure exposure. So were biology factors, specified arsenic vulnerability to pollution from burning coal with a precocious fluoride content.

The studies were grouped into 3 categories: those successful which vulnerability was little than 4 milligrams of fluoride per liter of h2o (the maximum concentration allowed successful the U.S. by the Environmental Protection Agency); those successful which vulnerability was little than 2 mg/L (the EPA’s non-enforceable secondary standard to forestall cosmetic problems successful places wherever fluoride levels are people high); and those successful which vulnerability was little than 1.5 mg/L (the guideline value acceptable by the World Health Organization).

So what’s the nexus with IQ?

Of the 65 studies included successful the superior analysis, 64 recovered an inverse narration betwixt fluoride vulnerability and children’s IQ — the higher (or lower) fluoride was, the little (or higher) IQ scores were.

The researchers besides pooled unneurotic information connected astir 21,000 children from 59 studies that reported mean IQ scores. Those information showed that children exposed to higher fluoride levels had little IQ scores than children exposed to little fluoride levels.

In addition, the study authors combined information from 38 studies and crunched the numbers themselves to spot whether determination was an wide dose-response narration betwixt fluoride and IQ. Sure enough, they wrote, “lower children’s IQ scores were associated with expanding levels of fluoride exposure.”

This sounds bad. Should I beryllium worried?

Not necessarily. The findings are only arsenic strong arsenic the information they’re based on, and the studies successful this investigation person immoderate issues.

For starters, 52 of the 74 studies were judged by the study authors to person a “high hazard of bias.” That undermines the validity and reliability of their results.

Another contented is that astir of the studies considered fluoride exposures acold supra the people level for the U.S. Since 2015, the Public Health Service has pegged the “optimal” attraction of fluoride astatine 0.7 mg/L, the equivalent of astir 3 drops of fluoride successful a 55-gallon barrel. (Prior to that, the people ranged from 0.7 to 1.2 mg/L.)

Only 7 of the studies assessed children whose h2o contained little than 1.5 mg/L of fluoride. When they were considered connected their own, determination was nary narration betwixt fluoride vulnerability and IQ.

Besides, the American Academy of Pediatrics has noted that assessing IQ successful children is not a straightforward affair, since measurements tin beryllium skewed by “socioeconomic, physical, familial, cultural, genetic, nutritional, and biology factors.” Comparing IQ scores from aggregate studies successful aggregate countries arsenic if they were the aforesaid lone compounds the problem, the academy said.

Hmmm. What other should I cognize astir this report?

Plenty. In fact, JAMA Pediatrics published an editorial by Dr. Steven M. Levy, a dental nationalist wellness adept from the University of Iowa, to enumerate the reasons wherefore the study shouldn’t beryllium taken astatine look value.

Take the contented of bias. Of the 59 studies that comprised the bosom of the analysis, lone 12 had a debased hazard of bias, and 8 of them recovered nary inverse transportation betwixt fluoride and IQ, Levy wrote.

Then there’s the usage of urine to measurement fluoride exposure. The study authors touted this arsenic a much precise mode to measurement an individual’s vulnerability to fluoride from each sources, not conscionable drinking water. But that reasoning is contrary to the “scientific consensus,” Levy wrote. Urinary fluoride measurements alteration importantly implicit the people of a time and from 1 time to the next, truthful there’s nary mode to know whether immoderate peculiar illustration is indicative of a person’s semipermanent exposure.

Levy besides chided the study authors for cherry-picking the studies they included successful their analysis. For instance, fixed the prime of 2 publications based connected information from the Canadian Maternal-Infant Research connected Environmental Chemicals study, the study authors opted against the 1 that included fluoride vulnerability aft birth. The work they omitted recovered nary nexus betwixt “fluoride vulnerability during pregnancy, infancy, oregon puerility and full-scale IQ,” helium wrote.

Other recent, high-quality studies showing nary relation got abbreviated shrift arsenic well, helium added.

Is that all?

There are different critiques astir methodology and statistical analysis. But 1 of Levy’s biggest complaints astir the study is the “lack of transparency” astir its backstory.

The authors downplayed the report’s nexus to the arguable monograph they produced for the National Toxicology Program, Levy wrote. The archetypal 2 drafts of that monograph received harsh adjacent reviews from the National Academies of Science, Engineering and Medicine. The archetypal mentation lacked wide grounds to enactment the authors’ assertion that “fluoride is presumed to beryllium a cognitive neurodevelopmental hazard to humans,” and the 2nd 1 glossed implicit the information that it wasn’t equipped to shed airy connected the risks posed by the debased attraction of fluoride successful U.S. h2o systems, the NASEM reviewers said.

Nor, Levy wrote, does the caller study notation that carnal studies utilizing fluoride levels that bespeak the U.S. modular of 0.7 mg/L recovered “no exposure-related differences successful motor, sensory, oregon learning and representation performance” successful astir a twelve tests, arsenic researchers reported successful 2018.

How tin I archer whether fluoride is being added to my water?

State and section authorities determine for themselves whether to fluoridate the h2o supply. In immoderate places, the h2o is people precocious successful fluoride due to the fact that determination happens to beryllium a batch of it successful the ungraded and bedrock. If the attraction is higher than 2.0 mg/L, the EPA requires officials to notify radical who portion that h2o wrong 12 months. If the attraction exceeds 4.0 mg/L, officials indispensable notify radical wrong 30 days and instrumentality steps to trim fluoride to harmless levels.

Nearly 63% of Americans person fluoridated water, including the 3.5% whose fluoride levels transcend optimal levels, according to the CDC. If you privation to spot whether your h2o strategy adds fluoride, effort looking it up connected the CDC website. (Depending connected wherever you live, you whitethorn person to interaction your h2o supplier directly.)

If you unrecorded successful Los Angeles County, you tin usage this map to spot whether you’re among the 62% receiving “optimally fluoridated” water, the 5% whose h2o is “largely fluoridated,” the 22% whose h2o is “partially fluoridated,” oregon the 11% whose h2o isn’t fluoridated.

That doesn’t mean the h2o is fluoride-free: According to the Los Angeles Department of Water and Power, the city’s groundwater contains fluoride astatine concentrations ranging from 0.1 to 0.3 mg/L, and fluoride levels successful the h2o supplied by the Los Angeles Aqueduct scope betwixt 0.4 and 0.8 mg/L. All h2o delivered by the DWP is adjusted to a fluoride attraction of 0.7 mg/L, the bureau says.

So what’s the bottommost line?

The study authors acknowledged that their investigation “was not designed to code the broader nationalist wellness implications of h2o fluoridation successful the United States.” Even so, they suggested that their findings “may pass aboriginal nationalist wellness risk-benefit assessments of fluoride.”

A second editorial that accompanies the study said it raises capable questions to warrant a reassessment of “the imaginable risks of fluoride during aboriginal encephalon development.” The deficiency of a wide nexus betwixt IQ scores and fluoride vulnerability beneath 1.5 mg/L “does not exonerate fluoride arsenic a imaginable risk,” the editorial argued.

Levy disagreed. “There is nary grounds of an adverse effect astatine the little h2o fluoride levels commonly used” successful h2o systems successful the U.S., helium wrote. “The wide usage of fluoride for [cavity] prevention should continue.”