Fluoride—a naturally occurring mineral—is in most public water systems throughout the United States. Indeed, water fluoridation was one of the most important public health prevention strategies implemented in the 20th century. Most public water sources added fluoride for several decades now, which means we are starting to learn the health implications on our population.
At the beginning of the 20th century, dental scientists began exploring why many people had brown stains that covered whole teeth. Before research began, many theories circulated about why brown stains were prevalent, including overeating pork or drinking poor 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 persisted, and eventually, fluoridated water became a solution to preventing tooth decay. Today, fluoride is in nearly every toothpaste, and most Americans using public water sources drink fluoridated water.
Fluoride is a mineral that naturally releases from rocks into groundwater. Nearly every natural water sources contain some fluoride, but it is usually not enough to prevent tooth decay. Fluoride prevents tooth decay by keeping tooth enamel healthy in the presence of oral bacteria that feed off of sugar. These bacteria release acid that breaks down tooth enamel, causing cavities.
Preventing cavities is a public health concern because cavities are one of the most common childhood diseases. Fluoride is an excellent solution for preventing tooth decay. Some of its benefits include protecting teeth across all ages, reducing the number of hours lost from school and work to address dental issues, and reducing health care costs.
Access to fluoridated water has been widely available for several decades. Within the last few years, concerns have grown about how fluoridated water affects the thyroid.
Some studies indicate that high fluoride exposure increases a person's risk for hypothyroidism, especially if they have an iodine deficiency. A 2015 study from the United Kingdom measures thousands of patients' thyroid labs compared to maximum water fluoride concentrations. Results show that patients living in fluoridated water areas have a higher prevalence of hypothyroidism compared to those without fluoride in their water.
There has been much criticism about the results of this study. One of the primary complaints is that the research was not well controlled because many factors affect hypothyroidism. For example, this study did not account for age, sex, or autoimmune disease. Indeed, most people with hypothyroidism in the United Kingdom have low thyroid function because of Hashimoto's (autoimmune thyroiditis). Similarly, 20-30% of patients were on levothyroxine because of medically-induced hypothyroidism after radiation or surgical treatment for hyperthyroidism. Generally, there is concern that this study's evidence is too weak to conclude that fluoride is a causative factor in hypothyroidism.
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 and iodine are halogens—a group in the periodic table consisting of five chemically related elements: fluorine, chlorine, bromine, iodine, and astatine. The name "halogen" means "salt-producing." When halogens react with metals, they produce salts, including calcium fluoride, sodium chloride (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 critical in producing the thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Without iodine, the thyroid cannot make thyroid hormones responsible for regulating metabolism, growth, and development.
Because fluorine is structurally similar to iodine, it may take up receptor sites in the thyroid gland, inhibiting iodine absorption. This, in turn, may cause iodine deficiency.
One way that fluoride inhibits iodide transport is by its stronger electronegativity. Thus, fluoride is more likely to enter membrane channels in the thyroid, forcing iodide out of thyroid cells. Some theories suggest that fluoride enhances the effects of thyroid-stimulating hormone and interferes with the conversion of T4 to T3.
Interestingly, there is also controversy about how much iodine people should ingest. Some studies find that taking in too much iodine may also inhibit thyroid function and lead to Hashimoto's. Iodine may increase the TPO antibodies' activity, which attacks TPO enzymes critical for synthesizing thyroid hormones. When TPO antibodies detect an increase in the TPO enzyme activity, the immune system ramps up its attack on the thyroid gland. Thus, Hashimoto's symptoms and hypothyroidism may worsen in the presence of excess iodine.
Some people report improvement in thyroid symptoms and thyroid levels when they remove halogens from their lifestyle. Household water purification systems like reverse osmosis, electrodialysis, activated carbon, or other adsorption/ion-exchange methods may be a good idea for hypothyroid patients. These systems can help remove fluoride.
Hydration is a pillar of your health, so having fluoride-free drinking water available may be beneficial! Indeed, 60-75% of your body is water, so drinking more has a considerable impact on your weight, energy, mental clarity, and whole-body health.
Forget the "eight glasses a day" rule and drink as much as you need. Aim for half of your body weight (lbs) in ounces of water every day. Paying attention to your water intake is one of the lowest efforts with the highest impact you can do starting right now.
While there seems to be some evidence that fluoridated water may worsen hypothyroidism, studies currently lack concrete evidence. We know that fluoride in water solved one of the most significant childhood health concerns. It also improved the quality of life in children and adults and has decreased health care costs. However, we do not yet know the extent of fluoride's effects on the thyroid, although the relationship does need more exploration.
If you are struggling with hypothyroid symptoms, talk with a trustworthy thyroid doctor to optimize your thyroid function.
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