Fluoride and the Thyroid
- Jun 27, 2025
- 8 min read
Updated: Nov 11, 2025
There’s a lot of discussion online about fluoride these days, especially after a recent claim from a government official that fluoride in drinking water “calcifies the thyroid.”
That’s...not how any of this works.
I went down the rabbit hole and read the studies about what fluoride really does (and doesn’t do) when it comes to the thyroid (and spoiler alert: iodine status matters in this context).
What Fluoride Does
Fluoride is best known for its dental benefits. At standard levels in drinking water (~0.7 mg/L in the U.S.), it helps remineralize enamel and reduce cavities. At higher exposures, it has been linked to thyroid hormone disruption, elevated TSH, and neurodevelopmental concerns. So we all are rightfully asking questions about it being in our drinking water.
What Fluoride Does Not Do
It does not calcify your thyroid. No credible evidence supports this claim (I honestly couldn't find any evidence at all, credible or not). It also does not destroy your thyroid overnight. the research out there is on long-term, high-level exposure, often combined with low iodine intake.
Thyroid Calcification
This is where the confusion probably started: yes, thyroid calcifications exist, but they are not caused by fluoride.
Thyroid calcifications typically form due to:
Chronic inflammation, like in Hashimoto’s thyroiditis, where long-standing tissue damage can lead to small calcium deposits
Benign nodules, which may become partially calcified over time
Certain types of thyroid cancer, especially papillary thyroid carcinoma, which can produce microcalcifications visible on ultrasound
These calcifications are your body’s response to inflammation or tissue remodeling, not something triggered by fluoride in water. They're often picked up incidentally during imaging and are not the same thing as fluoride “coating” or “hardening” your thyroid (I pictured like a hard bony shell around they thyroid when I first heard this mentioned, and that just doesn't happen).
Here's the Research for my extra nerdy friends. Shhh, don't tell anyone, but you're my favorites
A 2024 systematic review found effects on thyroid hormones that was dose-dependent, meaning the more fluoride, the more disruption, but they also noted that all of the studies reviewed had flaws. Another 2024 meta-analysis (these are the studies that look at all the available other studies and combine their data) found that at 2.5 mg/L fluoride (which is over 3 times the targeted range in U.S. drinking water), thyroid dysfunction began to appear. A 2018 case control study found higher TSH at 0.3–0.5 mg/L of fluoride int he water, though TSH was still within the normal range. Important to note: most studies did not control for iodine status, which can make a big difference!
The Iodine Factor
Fluoride and iodine are both halogens. That means they have similar chemical structures and can sometimes compete for the same spots in the body.
One of those spots is the sodium-iodide symporter (NIS), a kind of docking station that pulls iodine into your thyroid so it can make hormones like T3 and T4. But if fluoride gets there first, it can block iodine from docking, which means less iodine gets into the gland.
When this happens:
T3 and T4 levels may drop
The brain responds by ramping up TSH, trying to “yell” at the thyroid to work harder
Over time, this can lead to or worsen hypothyroidism
And in people with autoimmune conditions like Hashimoto’s, it may trigger more inflammation and antibody production, since the body is reacting to the imbalance
So, if you have too much fluoride AND not enough iodine, it can throw off the balance your thyroid needs to function properly. At the fluoride levels you'll find in most U.S. drinking water (~0.7 mg/L), your body typically has more than enough docking stations (NIS) for iodine if you’re eating an iodine-replete diet.
In fact, a Canadian population study confirmed this. The average fluoride level was about 0.74 mg/L, and they found that only people with moderate-to-severe iodine deficiency showed increases in TSH as fluoride went up. Those with adequate iodine saw no change in TSH despite the same fluoride exposure.
Always remember to test your iodine status before supplementing, and no mega-doses, since Iodine can put the autoimmune attack in Hashimoto's on steroids (I have another post here all about this). If you need to get labs, I also have a post here explaining how to do that yourself.
So, bottom line, should we worry?
At the levels in US community drinking water, probably not. You can test your water (especially if you’re on a well), avoid unnecessary extra fluoride if you have Hashimoto’s, and test your iodine levels if you’re unsure. For most people, risks are low.
That said, if you're trying to conceive or are pregnant, you do need to be more cautious. Fluoride crosses the placenta and can reach the fetus during critical windows of brain development. Multiple studies (including large, well-designed ones) have found that higher maternal fluoride levels during pregnancy are linked to lower IQ and more behavioral problems in children:
A 2017 Canadian study published in JAMA Pediatrics found that each 1 mg/L increase in urinary fluoride during pregnancy was associated with a 1.6-point drop in child IQ.
A 2024 U.S. study found a significant increase in emotional and behavioral issues (including anxiety and somatic complaints) among toddlers whose mothers had higher fluoride exposure during pregnancy.
A 2025 NIH-funded meta-analysis (also in JAMA Pediatrics) confirmed these findings across 74 studies from 10 countries. Even in high-quality, low-bias studies, a 1 mg/L rise in urinary fluoride was associated with a 1.14–1.63 point drop in IQ.
Note: There wasn’t strong evidence of harm at water fluoride levels below 1.5 mg/L, but prenatal and urinary fluoride exposures still showed consistent downward shifts in IQ across the exposure range.
Animal studies back this up, showing that prenatal fluoride exposure can affect brain structure, increase inflammation, and alter neurotransmitter levels.
While these risks are still being studied, there’s no clear benefit to fluoride exposure during pregnancy (since it doesn’t help fetal dental health), and the emerging evidence suggests a potential for harm, especially at levels commonly found in U.S. tap water.
So if you’re pregnant or TTC, switching to filtered fluoride-free water is a smart choice.
Filter Options
Most standard pitcher filters (like Brita or PUR) and built-in fridge filters don’t touch fluoride at all. Here’s what does work:
Reverse Osmosis (RO) Systems
Removes 90–95% of fluoride
Also filters out heavy metals, PFAS, chlorine, and other contaminants
Good brands: APEC, Home Master, Aquasana OptimH2O
Important note: Reverse osmosis also strips out beneficial minerals like magnesium and calcium. If you're using RO water long-term, be sure to add trace minerals back in, either with liquid mineral drops or by using a remineralization cartridge. This supports hydration, electrolyte balance, and overall mineral status (which is especially important if you’re dealing with thyroid or adrenal issues).
Activated Alumina Filters
Removes up to 90% of fluoride
Available in countertop gravity systems (like Berkey with fluoride add-ons)
Needs regular maintenance for full effectiveness
Bone Char Carbon Filters
Removes around 80–90% of fluoride
A more natural alternative to synthetic media
Found in some gravity systems and whole-house setups
Let's Talk Toothpaste
Fluoride was first added to toothpaste, not water. It works topically. You brush, spit, but don’t rinse so it stays in your saliva and strengthens enamel from the outside. That’s why using fluoride toothpaste can still be useful, especially if you're filtering it out of your drinking water.
If you’d rather avoid fluoride entirely, nano-hydroxyapatite (nHA) is the top science-backed alternative. nHA is the mineral that makes up tooth enamel. It works by actually rebuilding enamel by filling in microscopic damage and fortifying your teeth against decay.
One of the best parts about it is that nHA dissolves in the stomach, not accumulating in the body. So unlike fluoride, nHA is safe even if swallowed, so it's perfect for young kids who aren’t great at spitting yet, or anyone trying to keep fluoride systemically low (like during pregnancy). You may have heard to avoid the nano sized particles because of the possibility of it damaging cells or somehow going into the body and causing hardening. This is probably because the EU banned some of it in cosmetics due to safety concerns, but the nHA used in cosmetics is in a different shape than the nHA in toothpaste.
What to Look For (and What to Avoid) In nHA Toothpaste
Choose a product that uses rod-shaped nano-hydroxyapatite, not needle-shaped particles (those are the ones banned in EU cosmetics; they aren’t used in reputable toothpaste brands).
Look for at least 10% nHA concentration, the level supported in studies.
Final Thoughts
Fluoride benefits teeth, but high exposure along with low iodine could potentially impact the thyroid, and you may want to avoid even the low levels in municipal water if you're trying to conceive or are pregnant.
A Possibly Unpopular Side Note
I understand why so many people are drawn to the MAHA movement. I’m with you: we should be fighting for real food, clean water, and fewer toxic exposures for our families. But when a movement makes claims like “fluoride calcifies the thyroid” without evidence, it weakens trust, and that makes it harder to tackle the very real threats we’re up against. I mean, don't they have interns to do some Google Scholar fact checking? It's happened more than once, so it wasn't just an "he misspoke" moment. It even happened in the MAHA Report.
Here’s where I'm confused: while MAHA is fighting for food quality, the current administration is quietly rolling back protections on toxins that directly affect our hormones, immune systems, and thyroids:
PFAS ("forever chemicals"): The EPA delayed and weakened standards for PFAS cleanup, even though these chemicals are linked to hormone disruption, cancer, and thyroid disease.
Endocrine-disrupting chemicals (EDCs): Restrictions on pesticide and plasticizer regulation have been loosened, despite widespread evidence that EDCs disrupt hormone balance and fetal development.
Mercury emissions: Limits on power plant mercury output (originally designed to protect pregnant women and children) are being reversed.
Water protections: Rollbacks mean industrial pollutants have an easier path into our drinking water and soil. If we're fighting to remove fluoride, but allowing other, potentially more harmful toxins in, what's the point?
Asbestos: The ban is being reconsidered, despite clear links to cancer and lung disease.
USDA leadership: A former seed oil lobbyist was appointed to a top USDA role, putting corporate interests ahead of nutrition and public health.
So yes, let’s talk about dyes, additives, and fake ingredients, but let’s also talk about how regulatory choices are setting public health back. The same people talking about protecting kids are simultaneously gutting protections against the chemicals that hurt them most. The MAHA moms should be as outraged by this as I am.
So, bottom line, the movement needs to stay grounded in science. When the facts are solid, the case for change is clear. But when misinformation creeps in, it becomes a distraction, and we can’t afford that right now. Our families deserve to have clean food and water more than corporations need to make even more money off lifted restrictions.
If you're dealing with thyroid issues and need a practitioner who will test the right things and create a lifestyle, supplement & nutrition plan that works, please reach out!
If you like what you’re learning here, you’ll love the conversations happening inside my free Facebook group, Find Your Balance. Come join us!
References
Disclaimer: I do not diagnose, treat, prevent, or cure any disease or condition. Nothing I share is intended to substitute for the advice, treatment or diagnosis of a qualified licensed physician. I may not make any medical diagnoses or claim, nor substitute for your personal physician’s care. It is my role to partner with you to provide ongoing support and accountability in an opt-in model of self-care and any changes should be done under the supervision of a licensed physician.
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