Fluoride: Benefits, Dosage, and Safety

What fluoride is

Fluoride is the ionic form of the element fluorine and is classified as a mineral. It is naturally present in trace amounts in soil, water, plants, and foods, and it is also available in a few dietary supplements. Most fluoride that people consume comes from fluoridated drinking water, foods and beverages prepared with fluoridated water, and fluoride-containing dental products such as toothpaste. About 80% or more of orally ingested fluoride is absorbed in the gastrointestinal tract; in adults roughly 50% of absorbed fluoride is retained (almost all stored in bones and teeth) and about 50% is excreted in urine, while young children retain up to 80%.

What it does

• Inhibits or reverses the initiation and progression of dental caries (tooth decay) by inhibiting demineralization and reducing the activity of bacteria in dental plaque
• Enhances remineralization of tooth enamel
• Stimulates new bone formation and is stored in bones and teeth
• Is incorporated into the mineral structure of developing teeth and bone

How much fluoride per day

These are population reference values from the NIH and the Dietary Reference Intakes. They are targets for healthy people, not personal prescriptions. The last column is the Tolerable Upper Intake Level, the most you should get from all sources combined.

Deficiency and who is at risk

The Food and Nutrition Board did not establish an EAR or RDA for fluoride and there is no defined classical deficiency disease. Inadequate fluoride intake is associated with a higher risk and severity of dental caries (tooth decay), which fluoride helps to inhibit. Criteria for adequate, high, or low levels of fluoride in the body have not been established.

Who may need more

• Children age 6 months and older living where community water contains little or no fluoride, for whom the USPSTF and American Dental Association recommend fluoride supplements
• Children age 6 months to 3 years in areas with water below 0.3 mg/L (ADA: 0.25 mg/day)
• Children age 3-6 years in low-fluoride areas (ADA: 0.25-0.5 mg/day depending on water level)
• Children age 6-16 years in low-fluoride areas (ADA: 0.5-1 mg/day depending on water level)

Food sources

Brewed black tea is among the richest sources at 0.07 to 1.5 mg per cup (tea plants take up fluoride from soil). Other sources include brewed coffee (about 0.22 mg/cup), canned shrimp (0.17 mg per 3 oz), bottled water with added fluoride (up to 0.17 mg/cup), raisins, cooked oatmeal, grapefruit juice, and baked potato (about 0.08 mg each). Most other foods not prepared with fluoridated water provide less than 0.05 mg per 100 g. Fluoridated municipal drinking water and foods and beverages made with it account for about 60% of fluoride intake in the United States; the recommended fluoridation level is 0.7 mg/L.

Forms and absorption

Only a few dietary supplements contain fluoride, usually as sodium fluoride, most often in multivitamin/mineral products, multivitamins plus fluoride, or trace-mineral supplements. Pediatric supplements are often supplied as drops. The most common amount is 0.25 mg per serving, with some products providing 0.5 or 1 mg. In toothpaste, fluoride is present as sodium fluoride or monofluorophosphate, typically at 1,000 to 1,100 mg/L (about 1.3 mg in a quarter teaspoon), and is well absorbed regardless of form. Water fluoridation additives are fluorosilicic acid, sodium fluorosilicate, and sodium fluoride.

Safety, excess and interactions

Too much

Long-term ingestion of excess fluoride during infancy and childhood, while teeth are forming, can cause dental fluorosis, ranging from faint white lines or flecks to white or brown staining and, in severe cases, pitting of tooth enamel; severe dental fluorosis is rare and is not caused by the recommended level of fluoride in public tap water. Chronic excess intake is also associated with skeletal fluorosis, whose effects can range from occasional joint pain or stiffness to osteoporosis, muscle wasting, and neurological defects, though skeletal fluorosis is extremely rare in the United States. High acute doses, typically from accidents or inappropriate ingestion of dental products, can cause nausea, vomiting, abdominal pain, diarrhea, periostitis, and in rare cases death; the acute dose estimated to cause serious systemic toxicity is 5 mg/kg (for example, about 375 mg for a 75 kg person), which is virtually impossible to reach from water or toothpaste at standard fluoride levels.

Interactions to know

• Fluoride has no known, clinically relevant interactions with medications, according to the NIH Office of Dietary Supplements
• Voriconazole (an antifungal) contains fluoride as a constituent; long-term use (about 4 months or more) can raise serum and plasma fluoride and lead to skeletal fluorosis or periostitis, and prescribing information advises discontinuation if these develop

How status is measured

Not routinely measured. Individual fluoride status is not typically assessed, and criteria for adequate, high, or low body levels have not been established. When measured for research or exposure monitoring, fluoride concentrations can be determined in plasma, saliva, urine, bones, nails, hair, and teeth.

Fluoride is regulated as a dietary ingredient and appears in a small number of dietary supplements (usually as sodium fluoride), which are not FDA-approved to treat, cure, or prevent disease. The FDA limits total fluoride in bottled water with added fluoride to 0.7 mg/L. The EPA regulates fluoride in public drinking water (maximum allowable 4.0 mg/L; secondary recommended 2.0 mg/L). The U.S. Public Health Service recommends a fluoridation level of 0.7 mg/L. Fluoride is not among the nutrients with a Daily Value on Supplement Facts labels.

What the evidence supports

We grade the strength of evidence behind each common reason people take fluoride, mirroring how the NIH describes it.