Impact Of Fluoridated Water On Thyroid Health

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Fluoride—a naturally occurring mineral—has quietly flowed through most public water systems across the United States for decades. Touted as one of the 20th century’s most significant public health breakthroughs, water fluoridation has helped prevent countless cases of tooth decay since its widespread introduction. Now, after more than 70 years of continuous exposure, researchers are taking a fresh, closer look at what these long-term effects might mean for our thyroid and health in general, sparking new questions and renewed controversy about this mineral in our taps.

In this article, we’ll examine how fluoride works, the benefits it provides for dental health, and the potential concerns that have emerged over the years of exposure. We’ll also explore what current research says about its impact on your thyroid and overall health, helping you make informed choices for you and your family.

Fluoride is a mineral that is naturally released from rocks, and it’s found in water, soil, and many foods. Nearly every natural water source contains some fluoride.

At the beginning of the 20th century, dental scientists began to explore why many people had brown stains that covered whole teeth. Before research began, many theories circulated about why brown stains were prevalent, including the consumption of pork or drinking contaminated milk. However, early theories by dentists at the turn of the century speculated that water played a pivotal role in tooth decay. Over the next few decades, research continued, and eventually, experts discovered that fluoride was the key factor in preventing tooth decay.

Fluoride prevents tooth decay by keeping tooth enamel healthy in the presence of oral bacteria that feed on sugar. These bacteria release acid that breaks down tooth enamel, causing cavities. Preventing cavities is considered a public health concern because cavities are one of the most common childhood diseases.

The level of fluoride in drinking water is not naturally sufficient to prevent tooth decay. So authorities began to add fluoride to the water supply and dental products. Most of this commercial fluoride is actually made from an industrial waste byproduct, carefully purified for safety. This waste originates from factories that manufacture phosphate fertilizers.

Today, about 73% of Americans receive fluoridated water from community systems, according to the CDC’s 2024 Oral Health Surveillance Report. And, according to a 2025 survey conducted by the CareQuest Institute for Oral Health, about 86% of Americans use some form of fluoride, such as fluoridated toothpaste or mouthwash.

Beyond water and dental products, other sources of fluoride exposure include:

• Food, especially tea, some vegetables, and seafood
• Air near industrial emissions and coal plants
• Soil contaminated by industrial pollution and fertilizers
• Industrial pollution and fluoride waste releases
• Fluoride-containing pesticides and fumigants
• Beverages like tea and some processed drinks
• Occupational exposure in industries using fluoride chemicals

‍Access to fluoridated water has been widely available for several decades. Over the last few years, concerns have arisen about the potential effects of fluoridated water on the thyroid, as well as other ways fluoride can impact health. As a result, a growing number of municipalities have begun reconsidering or reducing fluoride levels, and experts are rethinking other exposures to fluoride, citing new research on possible systemic health effects.

On a broader level, recent concerns about fluoride have focused on its potential impacts on children’s brain development, dental health, and environmental exposure risks. The National Toxicology Program (NTP) report, released in August 2024, concluded with moderate confidence that fluoride exposure above 1.5 milligrams per liter in drinking water is associated with a lower IQ in children. It’s important to note, however, that this level is more than double the 0.7 mg/L recommended for U.S. community water fluoridation.

The NTP also noted there is not enough data to determine if the lower level currently used in the U.S. water supply has an effect on IQ, and there’s no evidence of adverse effects on adult cognition. The findings primarily came from studies in countries with significantly higher fluoride exposures than those typically experienced in the U.S. The report emphasized the need for more research on the effects of low-level fluoride exposure.

Additionally, a 2025 systematic review and meta-analysis of 74 studies found a statistically significant association between fluoride exposure and lower IQ scores in children, estimating a 1.63-point decrease in IQ for each 1 mg/L increase in urinary fluoride. This analysis reinforced concerns about neurodevelopmental risks at higher fluoride levels.

Some research suggests that high fluoride exposure may influence thyroid function, increasing the risk for hypothyroidism, particularly in individuals with iodine deficiency. A widely cited 2015 ecological study from the United Kingdom found a higher prevalence of hypothyroidism in areas with fluoridated drinking water compared to non-fluoridated regions. However, this study has been heavily criticized for design limitations, including a lack of adjustment for essential factors such as age, sex, and the high prevalence of autoimmune thyroiditis (Hashimoto’s disease) as the most common cause of hypothyroidism in the population studied. In addition, many patients were hypothyroid due to medical treatment for hyperthyroidism (thyroidectomy or radioiodine therapy), which is unrelated to fluoride exposure. Because of these methodological issues, experts caution that the findings are suggestive but not conclusive regarding fluoride as a causative factor in hypothyroidism.

The scientific debate has continued through 2025. Fluoride can chemically interfere with iodine because both are halogens. Iodine is an essential micronutrient required for the production of thyroid hormone – thyroxine (T4) and triiodothyronine (T3). Since the thyroid relies on iodine uptake for hormone production, structural similarities between fluoride and iodine have raised concerns that fluoride competes with iodine at the cellular level. Fluoride may affect the way your thyroid functions in several ways. Because it’s more “attractive” to cells than iodine, it can sometimes crowd out iodine and make it harder for thyroid cells to take in what they need. Some studies also suggest that fluoride may interfere with the hormone signals that instruct your thyroid on how much hormone to produce, or it could slow down the process of converting the T4 storage form of thyroid hormone into its active T3 form, which your body actually utilizes.

Recent comprehensive reviews provide a more nuanced perspective. The 2024 National Toxicology Program report reported limited evidence that very high fluoride exposures (typically >1.5–2 mg/L in drinking water, often in areas without iodine sufficiency) may be associated with altered thyroid hormones. Still, it concluded that the evidence was insufficient to establish a cause-and-effect link between community water fluoridation (CWF) levels and thyroid problems.

A recent 2024 systematic review found that exposure to high levels of fluoride in drinking water was associated with changes in thyroid function, including higher thyroid-stimulating hormone (TSH) levels that may indicate reduced thyroid activity. Most of the studies included were from regions with naturally high fluoride concentrations, particularly in parts of Asia. The authors emphasized, however, that many of these studies had methodological limitations, potential complicating factors such as iodine intake, and varied study quality—making it difficult to draw firm conclusions, especially at the much lower fluoride levels used in U.S. community water fluoridation.

Despite the controversy over whether fluoride causes hypothyroidism, fluoride may play a role in thyroid function because it shares similar properties with iodine.

Both fluorine – the elemental form of fluoride -- and iodine are halogens. This group in the periodic table consists of five chemically related elements: fluorine, chlorine, bromine, iodine, and astatine. The name “halogen” means “salt-producing.” When halogens react with metals, they form salts, including calcium fluoride, sodium chloride (common table salt), silver bromide, and potassium iodide. Most halogens come from minerals or salts in the sea and soil.

Iodine does not occur naturally in the body, so people must ingest iodine in their diet. This micronutrient is crucial in the production of thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3). Without iodine, the thyroid cannot produce thyroid hormones, which are responsible for regulating metabolism, growth, and development.

Because fluorine is structurally similar to iodine, it can occupy receptor sites in the thyroid gland and inhibit iodine absorption. This, in turn, may cause iodine deficiency.

While iodine deficiency is a well-established cause of goiter and hypothyroidism, Interestingly, there is also controversy about how much iodine people should ingest, as excess iodine intake may also impair thyroid function and trigger or exacerbate autoimmune thyroiditis (Hashimoto’s disease). This paradox means that both insufficient and excess iodine can disturb thyroid hormone balance. As a result, evaluating fluoride’s impact cannot be separated from the nutritional and autoimmune status of each population.

At levels used for community water fluoridation (approximately 0.7 mg/L), the current body of evidence does not consistently demonstrate adverse effects on thyroid function, although research continues and some uncertainties remain.

At the same time, the current consensus is that excess fluoride at high levels may contribute to thyroid dysfunction in iodine-deficient populations. Experts believe that fluoride’s contributions to thyroid dysfunction and health problems are in combination with other factors — including genetics, iodine status, and autoimmune activity — rather than fluoride acting as a sole cause.

Recent concerns about fluoride have also focused on its potential impacts on children’s brain development, dental health, and environmental exposure risks. The 2024 National Toxicology Program report concluded with moderate confidence that fluoride exposure above 1.5 milligrams per liter in drinking water is associated with a lower IQ in children. It’s important to note, however, that this level is more than double the 0.7 mg/L recommended for U.S. community water fluoridation.

The NTP also noted there is not enough data to determine if the lower level currently used in the U.S. water supply has an effect on IQ, and there’s no evidence of adverse effects on adult cognition. The findings primarily came from studies in countries with significantly higher fluoride exposures than those typically experienced in the U.S. The report emphasized the need for more research on the effects of low-level fluoride exposure.

Additionally, a 2025 systematic review and meta-analysis of 74 studies found a statistically significant association between fluoride exposure and lower IQ scores in children, estimating a 1.63-point decrease in IQ for each 1 mg/L increase in urinary fluoride. This analysis reinforced concerns about neurodevelopmental risks at higher fluoride levels.

Finally, fluoridated water also raises concerns about dental fluorosis, a condition that affects the appearance and structure of tooth enamel. Dental fluorosis is caused by excessive exposure to fluoride during the years when teeth are developing, typically in children under the age of eight. In areas where water is fluoridated, most people receive a safe, low dose intended to prevent tooth decay, also known as cavities. However, concerns arise when fluoride levels exceed recommended limits, as this can lead to mild to moderate dental fluorosis. Mild cases often appear as faint white streaks or spots on the teeth, while more severe forms can cause brown discoloration, tooth mottling, pitting, or enamel fluorosis, which can impact both the appearance and strength of the teeth.

Public health authorities generally agree that the benefits of water fluoridation—primarily reducing tooth decay—outweigh the risks associated with it. Still, some parents and health advocates worry that even low-level chronic exposure in young children could increase the likelihood of fluorosis, particularly in communities with naturally high fluoride levels or where multiple fluoride sources are used, such as toothpaste, mouth rinses, and supplements.

As of September 2025, two states—Utah and Florida—have officially banned fluoridated water in public systems, with legislation in both states taking effect in 2025. Numerous other states, such as Kentucky, Massachusetts, New Hampshire, Nebraska, and Louisiana, have introduced bills to ban or reduce the amount of fluoride in water. Still, these have not yet been passed statewide.

These developments are raising alarms among pediatricians and dental experts who warn that these bans could lead to increased tooth decay, especially in low-income and rural populations. Projections suggest a nationwide fluoride ban might lead to over 25 million additional decayed teeth in children over five years, increasing healthcare costs by billions and disproportionately impacting vulnerable groups.

Environmental debates continue because fluoride is primarily sourced from industrial waste byproducts, raising concerns about widespread exposure from multiple sources. While fluoride remains a significant public health success in cavity prevention and is supported by most dental professionals, scientific and public scrutiny continue to balance its benefits against emerging safety concerns, particularly for sensitive populations like pregnant women and infants.

If you and your doctor decide that controlling or reducing your fluoride exposure is a health goal or is advisable for your thyroid health, it can be achieved through several practical steps focused on minimizing intake from water, dental products, foods, and other consumer sources.

Check and filter your water

Water is often the most significant daily source of excess fluoride in communities with fluoridated drinking water. To reduce exposure:

• Find out your local tap water’s fluoride content by checking your Consumer Confidence Reports (CCR) or asking your water supplier.
• If fluoride levels are elevated, use water filters that are specifically designed to remove fluoride. Effective types include reverse osmosis systems, deionizers (ion-exchange resins), and activated alumina filters. Standard activated carbon filters, such as those made by Brita, do not remove fluoride.
• Spring water and distilled water (bottled water) usually contain very little fluoride. The Fluoride Action Network has a resource that can help you confirm the fluoride content listed by the bottler or manufacturer before you consume it regularly.

Safe dental care practices

Dental products are another common source of fluoride. You can lower your exposure by:

• Supervising children while brushing to prevent swallowing toothpaste and using only a pea-sized amount.
• Choosing fluoride-free toothpaste and mouthwash, especially for younger children or if your dentist recommends it.
• Limiting professional fluoride treatments unless specifically recommended due to increased cavity risk.

Rethink your diet and food choices

Fluoride can end up in foods and drinks processed using fluoridated water, including many packaged beverages, juices, and even tea.

• Increase consumption of fresh foods instead of processed foods and drinks made with fluoridated water.
• Choose organic produce when possible to avoid residues from fluoride-containing pesticides.
• For infants, avoid making formula with fluoridated tap water.

The International Academy of Oral Medicine and Toxicology (IAOMT) offers a helpful guide on reducing fluoride exposure.

Additional everyday tips

Other lifestyle actions for reducing fluoride exposure include:

• Avoiding non-stick (Teflon) cookware, which may leach small amounts of fluoride.
• Checking pharmaceuticals, as some contain fluoride.
• Staying informed about regulatory changes, such as recent FDA measures to remove ingestible fluoride drug products for children.

By combining these steps, you can significantly reduce your overall fluoride intake and minimize potential health risks.

Fluoride has done a great deal of good over the years, helping to prevent cavities and improve dental health for both children and adults. However, researchers are still investigating how fluoride may impact the thyroid and brain. Some studies suggest that high fluoride exposure could be linked to changes in thyroid hormone levels, and there’s also evidence that it might affect IQ in children. Right now, the science isn’t definitive, but it’s worth being aware of how fluoride interacts with your body, especially if you already have thyroid health concerns.

If you’re experiencing any potential thyroid symptoms – such as fatigue, weight changes, or brain fog – it’s essential to get your thyroid checked. Paloma Health offers complete thyroid care, from convenient and accurate at-home testing to personalized treatment plans and ongoing guidance from thyroid specialists. Paloma’s approach is designed to help you feel your best by supporting healthy thyroid function and overall wellness. Paloma Health can help you take control of your health and get the care you need.

• Fluoride is a natural mineral added to water and dental products to prevent cavities.
• Approximately 73% of Americans receive fluoridated water, and around 86% use some form of fluoride daily.
• High fluoride exposure above 1.5 mg/L may lower IQ in children; however, typical U.S. levels are significantly lower.
• Fluoride can interfere with iodine uptake, which is essential for thyroid hormone production.
• Current evidence does not show consistent thyroid harm at U.S. water fluoridation levels.
• Individuals can reduce their fluoride exposure by using filtered water, fluoride-free dental products, and making informed dietary choices.

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