Fluoride's PR Nightmare
Keep Calm and Brush On
Fluoride is having a rough day in the court of public opinion. The National Toxicology Program (NTP), part of the Department of Health and Human Services, has released a comprehensive study titled "Monograph on the State of Science Concerning Fluoride Exposure and Neurodevelopment and Cognition."
The (supposed) bombshell finding? It linked high levels of fluoride—specifically, fluoride in drinking water at more than twice the recommended limit—with lower IQs in children.
TL;DR
The National Toxicology Program (NTP) released a study linking high fluoride levels (>1.5 mg/L) with lower IQs in children.
This level is more than double the amount used in U.S. community water fluoridation (0.7 mg/L).
About 0.6% of the U.S. population (1.9 million people) are exposed to these naturally high fluoride levels.
The American Dental Association (ADA) criticizes the study's methodology and maintains support for water fluoridation.
The study has significant limitations and does not provide evidence against current water fluoridation practices.
Do not throw out your fluoride toothpaste!
Now, let's discuss the details. This association between elevated fluoride exposure and decreased cognitive function in children has caused a lot of fear and anxiety (some of which I hope to quell in this newsletter). Adding weight to these findings, the NTP expressed 'moderate confidence' in this association, which seems significant coming from a federal agency. Let's be real, before this report was published, many people were already concerned about fluoride in water and toothpaste – much to the chagrin of dentists – and this isn't helping the situation.
But before we go further, let's get one thing crystal clear: this study does not provide evidence against current community water fluoridation practices. The NTP's findings are limited to fluoride exposures more than double (≥1.5 mg/L) the CDC-recommended level for community water fluoridation (0.7 mg/L).
According to the NTP report, about 0.6% of the U.S. population — approximately 1.9 million people — are on water systems with naturally occurring fluoride levels of 1.5 milligrams per liter or higher. It's important to note that these high levels are naturally occurring and not the result of artificial water fluoridation programs. Most community water fluoridation programs in the U.S. aim for a level of 0.7 mg/L, which is less than half the level associated with the findings in the NTP study.
The Study's Journey and Controversy
Interestingly, the publication of this report was delayed for several years. As Linda Birnbaum, a toxicologist and former head of the NTP, explained, "There was a great deal of concern raised, especially by the dental community, and they were concerned that this report would be misconstrued to say that any fluoridation of drinking water is a problem." This delay highlights the sensitivity of the issue and the potential for misinterpretation of the findings.
The American Dental Association (ADA) is not happy with the report (they issued a statement which you can read here). They've highlighted "significant limitations and biases within the report" which must be considered before accepting its conclusions. The ADA also pointed out that there were two previous drafts of the report in 2019 and 2020, both of which raised major red flags. The National Academies of Sciences, Engineering and Medicine, which was the original peer reviewer, reported that these earlier drafts "would not survive scientific scrutiny without major revision."
Of particular concern was a hazard assessment in these drafts stating that fluoride is "presumed to be a cognitive neurodevelopmental hazard to humans," regardless of exposure level. This assessment was later removed after the peer review committee found that the monograph fell short of providing a clear and convincing argument to support this claim.
The ADA criticizes the NTP for abandoning the original peer review process and instead hand-picking its own panel for the final draft. They also point out that the NTP failed to adequately address concerns raised by the National Academies, including inconsistent application of risk of bias criteria, inadequate statistical rigor, and selective reporting of non-significant study results. These issues, according to the ADA, persist in the latest version of the report, undermining its credibility and conclusions.
The Study's Aims and Findings
The NTP study aimed to:
Assess the evidence linking fluoride exposure to cognitive effects.
Evaluate this relationship in both human and animal studies.
Examine potential biological mechanisms for observed effects.
Key findings include:
A consistent association between higher fluoride exposure (above 1.5 mg/L in water) and lower IQ scores in children. It's important to note (again) that this level is more than twice the amount typically used in U.S. community water fluoridation programs (0.7 mg/L).
This finding was based on 19 high-quality studies, with 18 reporting an inverse association between fluoride exposure and IQ.
Only three of these were prospective cohort studies, limiting causal inferences.
The studies were conducted in 5 different countries with very different methodologies.
Animal studies provided little insight into fluoride's potential cognitive effects.
Human mechanistic studies were too limited to determine biological plausibility.
The evidence for effects on adult cognition was limited and inconclusive, further highlighting the focus of this study on children's cognitive development.
Now, putting on my data scientist hat: While meta-analyses can be powerful, it is important to remember that any threats to validity in each individual study get pooled (and potentially compounded) when the data are combined. This means that if there were any biases or confounding factors in the original studies, they could be amplified in the meta-analysis, potentially overstating the strength of the association.
Interestingly, the report doesn't address the benefits of fluoride for dental health, which has been a cornerstone of public health policy for decades. This omission is crucial for understanding the full picture and weighing the potential risks against the known benefits.
Several critical points need emphasis:
The study focused on fluoride levels significantly higher than those in U.S. water fluoridation programs.
None of the IQ studies were conducted in the U.S., but in areas with naturally high fluoride levels (limiting their generalizability).
The review didn't consider fluoride's dental health benefits or provide a risk-benefit analysis.
It didn't reach conclusions about risks at lower fluoride levels relevant to most public water systems.
Adult fluoride exposure effects weren't addressed.
While meta-analyses can be powerful, any threats to validity in individual studies get pooled and potentially compounded when data are combined.
The ADA's criticisms include inconsistent application of risk of bias criteria, inadequate statistical rigor, and selective reporting of non-significant study results, all of which persist in the latest report.
Quantifying the Impact
How much of an impact are we talking? The NTP report suggested IQ reductions in the range of 2 to 5 points in children with higher fluoride exposures (>1.5 mg/L). However, this should be interpreted cautiously:
This range was observed in studies with fluoride levels higher than U.S. water fluoridation programs.
Effect sizes varied across studies.
These are population averages, not individual guarantees.
More research is needed, especially at lower exposure levels.
It's crucial to understand that these potential IQ reductions are associated with the higher fluoride levels found in the study, not with the lower levels used in U.S. water fluoridation programs.
Balancing Risks and Benefits
We can't ignore fluoride's well-established dental health benefits. One study found a significant association between lower cognitive ability and poorer dental health, persisting even after controlling for confounders like income and ethnicity. This highlights the complexity of the issue and the need for a holistic approach to public health.
Public Perception and Misconceptions
Many people understand that "the dose makes the poison." As one commenter in my DMs aptly put it, "Anything at twice the normal limit will have negative health consequences. That's why there are limits." This principle is crucial in understanding the NTP's findings.
There's also a common misconception that the report's findings apply to areas where fluoride is added to water. In reality, the high levels of fluoride associated with potential IQ effects are primarily found in areas with naturally high fluoride concentrations.
Some individuals express concern about cumulative fluoride exposure from multiple sources, including water, toothpaste, and dietary sources. While this is a valid point for further research, current evidence doesn't suggest that normal use of fluoridated products in combination with optimally fluoridated water poses a risk.
The Bottom Line
While this study raises important questions about high-level fluoride exposure, it doesn't challenge current water fluoridation practices. The fluoride levels associated with potential IQ effects are significantly higher than those in community programs.
The CDC recognizes water fluoridation as one of the great public health achievements of the 20th century. As we continue researching fluoride's effects, it's crucial to maintain a balanced perspective, considering both potential risks at high exposures and well-established benefits at recommended levels.
In short, don't throw out your fluoride toothpaste. That's definitely not the takeaway here. Instead, this study underscores the need for continued research and monitoring, particularly in areas with naturally high fluoride levels in water sources.
A Note on Fluorosis
While we've focused on the potential cognitive effects of high fluoride exposure, it's worth briefly mentioning dental fluorosis. Fluorosis is a separate condition that can occur when developing teeth are exposed to excessive fluoride, resulting in visible changes to tooth enamel. While mild fluorosis is generally considered cosmetic, severe cases can cause more significant enamel defects. The fluoride levels associated with potential IQ effects in this study are significantly higher than those typically linked to fluorosis risk. As always, consult with your dentist or healthcare provider for personalized advice on fluoride use.
xo,
Jess