Fluoride 101: Health Evidence and Testing

Fluoride is a commonly known mineral, as 62.4% of people in the United States have access to fluoridated community water systems. Fluoride is commonly known for its impact on dental health but can also affect the skeletal system. This article will discuss what fluoride is, its role in the body, sources of fluoride, and how to test for it.

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What is Fluoride?

Fluoride was first isolated by French chemist Henri Moissan in 1886. Fluoride is created from the reaction of fluorine, a yellow gas in the earth’s crust, with minerals in rocks and soils. This reaction creates salts from which fluoride is made.

What is Fluoride's Role in The Body?

Fluoride has an absorption rate of around 80%. In adults, half of the fluoride is excreted in the urine, and the other half stays in the system, with almost all of it being stored in the bones and enamel of the teeth. Children tend to retain all the fluoride absorbed with little to no excretion due to the demand for growing bones and teeth.

Fluoride is known to support dental health by slowing demineralization while increasing mineralization of the enamel of teeth. Fluoride may help manage early tooth decay if exposed in the early stages. It can also inhibit the growth of bacteria that contribute to cavities. Because of these effects, it is estimated that fluoride can reduce the risk of cavities by 25%. Due to these benefits, fluoride is added to many dental products, including toothpaste, and is recommended for daily use. Fluoride treatment at dental offices is also recommended every six months.

Additionally, because of fluoride's effects on dental health, in 1962, the United States Public Health Service recommended adding fluoride to tap water, and it has been added ever since.

While fluoride can be beneficial for dental health, consumption of fluoride in high amounts for extended periods of time can negatively impact the teeth, causing dental fluorosis. Dental fluorosis causes discoloration of the teeth with either white or brown speckles and or streaks, and severe cases can cause pitting in the enamel. Dental fluorosis seems to be an emerging problem, as data extrapolated from the National Health and Nutrition Examination Survey (NHANES) between 2001-2002 showed mild to severe dental fluorosis rates at 29.7%; ten years later, that percentage jumped to 61.3%.

High amounts of fluoride can also lead to symptoms of abdominal pain, diarrhea, nausea, vomiting, periostitis (inflammation of the connective tissue surrounding the tibial bone, commonly known as “shin splints”), and even death. The amount of fluoride that achieves these symptoms is typically the result of accidental ingestion from children’s fluoride supplements, inappropriate fluoride levels in the water, or overconsumption of fluoride-containing products at dental offices.

Fluoride can also stimulate new bone growth. However, like dental fluorosis, high amounts of fluoride may also cause skeletal fluorosis, a condition with symptoms ranging from mild joint pain and stiffness to osteoporosis, muscle wasting, and neurological defects.

Fluoride may compete with iodine in the thyroid gland. Iodine is an essential nutrient for the creation of thyroid hormones. Thus, fluoride may negatively impact the thyroid.

How to Test Fluoride Levels

Fluoride levels may be measured in the urine. Doctor's Data offers a 24-hour urine collection test to assess urinary excretion of fluoride. As discussed above, half of the absorbed fluoride in adults will be excreted in the urine. Thus, this test will pick up on high fluoride levels in the body. The reference range for this test is a fluoride level of fewer than 1.1 milligrams (mg).

Fluoride Levels and Their Sources

The National Academy of Sciences, Engineering, and Medicine created the Food and Nutrition Board (FNB) to create guidelines regarding the intake of vitamins and minerals. Many vitamins and minerals have a Recommended Daily Allowance (RDA), the average daily intake that is considered enough to meet nutrition requirements for 97-98% of healthy individuals. For fluoride, however, there is not enough evidence to create RDAs. Instead, the FNB established daily Adequate Intakes (AI) dependent upon age and sex. AIs are levels assumed to be sufficient for proper nutritional values. Additionally, tolerable upper intake levels (ULs), defined as the largest intake that would not be likely to cause an adverse effect, were also established.

The AIs for pregnant and lactating women, who always get their own category due to the different nutritional demands in these populations, are set at 3mg and the ULs are 10 mg for both populations.

Sources of Fluoride

Fluoride can also be found in dental products, foods and beverages, certain medications, and supplements. Virtually everyone uses dental products and consumes food containing fluoride, so we'll look deeper into those categories.

Dental Products

Dental products, including toothpaste, mouthwashes, topical preparations (applied at dental offices and some school-based programs), and dental devices, contain fluoride. Toothpaste typically contains 1.3mg of fluoride per ¼ teaspoon. Fluoride from toothpaste is considered to be well absorbed, with the amount of fluoride absorbed varying from person to person depending on how often the person brushes, the amount of toothpaste used, and how well the person spits or swallows during brushing.

Foods and Beverages

There are small amounts of fluoride in foods due to soil content. Cooking in fluoridated water will also result in a negligible increase of fluoride in the food. Fluoridated water, and foods prepared in fluoridated water, account for 60% of fluoride intake in the United States.

It’s important to discuss the fluorination of water further. The initial level of fluoride added to water systems depended on the region, with 0.7 mg per deciliter (dL) in warmer climates where, hypothetically, more water is consumed and 1.2 mg/dL in colder regions. This was the status quo until 2015, when the level was changed to 0.7mg regardless of climate. It was thought this level was sufficient to reduce the risk of dental fluorosis while maintaining inhibition of dental caries, regardless of region. Additionally, in 1986 the Environmental Protection Agency (EPA) set the maximum allowable fluoride concentration in drinking water to 4.0mg/dL to prevent negative effects. However, they recommended a maximum concentration of 2.0mg/dL to prevent dental fluorosis, specifically. These recommendations have not been updated since their creation and are considered low priority for review by the EPA.

Summary

Fluoride has had an immensely positive impact on dental health, leading the Centers for Disease Control (CDC) to deem fluorination of water supplies one of the top ten public health achievements of the 20th century. However, care should be taken to avoid the risk of overconsumption as the negative impacts of fluoride can be significant; thus, testing fluoride levels may be advised when suspicion of overexposure occurs.