Fluoride is a naturally occurring element found in food and water. It occurs in the body as calcium fluoride, primarily in the teeth and bones. Fluoride is necessary for the development and maintenance of strong teeth and bones and helps prevent tooth decay (dental caries).


The importance of fluoride for dental health has been recognized since the 1930s, when an association between the fluoride content of drinking water and the prevalence of dental caries was first noted. Acids found in food and released by bacteria that feed on sugar in the mouth eat away at the enamel on the surfaces of the teeth. Systemic fluoride enters the bloodstream from food, water, and supplements and is incorporated into the enamel as the teeth develop. The enamel that covers the crown, the part of the tooth that is above the gum, is made of a substance called hydroxyapatite. If enough fluoride reaches the teeth while the enamel is forming, fluoride can replace a component of the hydroxyapatite molecule to form fluorapatite, becoming part of the tooth enamel. This makes the tooth more acid-resistant. Fluoride in saliva can also help repair enamel, making the new surface stronger than the original enamel and better able to resist decay, as well as reversing early decay. This process is called tooth remineralization or recalcification. Fluoride also interferes with the metabolism of bacteria in the mouth so that they produce less decay-causing acids.

Suggested amounts of dietary fluoride supplements


Fluoride ion level in drinking water (ppm)*

< 0.3 ppm

0.3-0.6 ppm

> 0.6 ppm

Birth6 months




6 months3 years

0.25 mg/day**



3 years6 years

0.50 mg/day

0.25 mg/day


6 years16 years

1.0 mg/day

0.50 mg/day


* 1.0 part per million (ppm) = 1 milligram/liter (mg/L)

** 2.2 mg sodium fluoride contains 1 mg fluoride ion

SOURCE: American Dental Association. “Fluoride: Topical and Systemic Supplements.” https://www.ada.org/en/member-centeroral-health-topics/fluoride-topical-and-systemic-supplements (accessed April 19, 2018).

Suggested amounts of dietary fluoride supplements, Children between the ages of 6 months to 16 years living in non-fluoridated areas may require dietary fluoride supplements.

It is unlikely that sufficient fluoride from water alone will be incorporated into the enamel during the years of crown formation. Thus, topical fluoride is the most effective means of remineralizing the surface layers of tooth enamel and dentin as they wear out and are eaten away by acids from food and bacteria. Topical fluorides are applied directly to the surfaces of fully formed teeth and help prevent tooth decay in both children and adults. Topical fluorides include fluoride toothpastes and mouthwashes and gels that are applied to children's teeth during dental examinations. Systemic fluorides, such as fluoridated water, can also provide topical protection, because they are incorporated into the saliva that bathes the teeth.

It is estimated that fluoridated water is 20%–60% effective in preventing cavities in children and adults. Early studies suggested that water fluoridation was eliminating tooth decay in children; however, other factors are now recognized as having contributed to the decline in dental caries. The widespread use of fluoridated toothpastes and mouthwashes has increased children's fluoride intake significantly. Furthermore, awareness of dental care and hygiene among both children and adults has increased in recent decades.


The element fluorine is the 17th most abundant element in the earth's crust. It occurs as a fluoride ion in combination with other elements such as sodium and calcium. Fluoride is present in small amounts in almost all soils, plants, and animals. It is found naturally in seawater and at low levels in most drinking water sources. Seawater contains about 1.5 parts per million (ppm) fluoride. Fluoride dissolves in water to form negatively charged fluoride ions (F-). In the body, this ion is absorbed into the bloodstream from the small intestine. It then binds with calcium in teeth and bones. The adult body contains less than 0.1 oz. (about 2.8 g) of fluoride, and 95% of this is in teeth and bones.

Fluoride requirements Fluoridated water

Water is the major source of fluoride for most people. In the early twentieth century, Frederick McKay, a young dentist in Colorado Springs, Colorado, noticed that many local residents had brown stains on their permanent teeth and that their teeth were surprisingly resistant to decay. McKay eventually discovered that this tooth “mottling” resulted from high levels of naturally occurring fluoride in the drinking water.

The first fluoridation of a public water system was in Grand Rapids, Michigan, in 1945. Over the following decades, more and more communities fluoridated their water using by-products from the phosphate fertilizer industry. About two-thirds of Americans now drink fluoridated water. However, fluoridation quickly became mired in controversy, and it remains so in the second decade of the twenty-first century. Since the decision to fluoridate is usually made at the local level, by public officials or popular vote, fluoridation is a political as well as a scientific controversy. While some opponents reject existing scientific evidence and claim that fluoridation is ineffective and/or harmful, for others, public water fluoridation is an issue of personal choice versus government control.

The levels of naturally occurring fluoride in fresh water range from less than 0.1 ppm to more than 13 ppm. The recommended level for preventing tooth decay is 0.7–1.2 ppm. Water fluoridation levels are usually at the low end of this range in warmer regions, where people tend to drink more water, and at the higher end of the range in colder regions. Filtered water and well water vary greatly in their fluoride content. Most bottled water contains only trace amounts of fluoride.

Adequate intake (AI)—
The daily average intake level of a nutrient that is likely to be adequate for a healthy, moderately active individual, as determined by the Institute of Medicine.
The calcified, dense tissue forming the bulk of a tooth beneath the enamel.
Dietary reference intake (DRI)—
A system of nutritional recommendations used by the Institute of Medicine of the U.S. National Academy of Sciences and the U.S. Department of Agriculture.
The hard mineralized tissue covering the dentin of the crown of a tooth.
Fluoride-substituted hydroxyapatite.
Mottling; spotting on the teeth due to excess fluoride during the forming of the tooth enamel.
Hydroxyapatite—Ca5(PO4)3OH; the material of tooth enamel consisting of calcium, phosphorous, oxygen, and hydrogen.
Fluorosis; spotting on the teeth due to excess fluoride as the tooth enamel is forming.
Recommended dietary allowance; RDA—
The approximate amount of a nutrient that should be ingested daily.
Recalcification; the process by which minerals from saliva and food are added to the surface of the tooth enamel or to the dentin.
A substance, such as fluoride, that is ingested, absorbed into the bloodstream, and distributed throughout the body.
Tolerable upper intake level (UL)—
The highest daily intake level of a nutrient that is unlikely to cause adverse health effects in almost all individuals in the general population, as determined by the Institute of Medicine.
A substance, such as fluoride, that is applied directly to the teeth.
Dietary sources of fluoride Other fluoride sources

Many toothpastes and mouthwashes contain high amounts of fluoride. A tube of fluoride toothpaste may contain as much as 1–2 g of fluoride. Nonprescription mouthwashes can contain up to 120 mg of fluoride. Children between the ages of two and six swallow about 33% of the toothpaste they use; children between seven and 15 swallow about 20%. Thus, an average child using a typical amount of fluoride toothpaste will swallow or absorb 0.5–1.0 mg of fluoride per brushing, although much of this fluoride is excreted. In addition, many vitamin supplements and medications contain fluoride.


The amount of fluoride occurring naturally in drinking water varies widely depending on the locale. People should be aware of whether their public water supply is fluoridated, and those with wells should have their water tested for fluoride. Bottled water suppliers can provide information about their water's fluoride content. Some built-in home water-softening systems may remove fluoride.

Although water fluoridation at levels that prevent tooth decay does not pose a health risk, high doses of fluoride can be toxic. Doses of 20–80 mg per day can cause bones to become chalky and brittle and can affect kidney function and possibly nerve and muscle function. Doses of 5–10 g per day can be fatal. In 2009, the American Association of Poison Control Centers reported 24,547 exposures involving fluoride toothpaste. Of these, 378 cases were treated in emergency departments, moderate effects were observed in 42 cases, and major effects in 2 cases. Most of these incidents involved children under age six who ate toothpaste. Too much fluoride in the diet is very rare.

At safe doses, fluoride does not appear to strengthen bones or prevent or delay osteoporosis (age-related thinning of the bones). Consequently, fluoride supplements are not an appropriate way to prevent or treat osteoporosis.



Antacids containing aluminum hydroxide and calcium supplements can decrease the absorption of fluoride from the small intestine.


There are no expected complications from daily doses of fluoride falling between the AI and the UL. Too little fluoride leads to increased tooth decay. Too much fluoride can cause illness or death. Too much fluoride, especially in children, also results in a condition called dental fluorosis. The surfaces of the teeth become discolored by chalky white splotches. This is a cosmetic problem and does not affect the health of the teeth. Fluoride poisoning is much more serious. A 40 lb. (18 kg) child would probably start to show symptoms of fluoride poisoning after consuming about 55 mg of fluoride (3 mg/kg of body weight), and a dose of 290 mg (16 mg/kg of body weight) would likely be fatal. Symptoms of fluoride poisoning include nausea, vomiting, diarrhea, headaches, muscle spasms, irregular heartbeat, coma, and death. Besides toothpaste and mouthwash, fluoride is also found in pesticides, rodent poisons, and chrome polish for automobiles.

Parental concerns

Rarely, infants who get too much fluoride before their teeth have broken through the gums have changes in the enamel that covers the teeth. Faint white lines or streaks may appear, but they are usually hard to see.

It is important to teach children to never eat toothpaste. This can be a problem, because toothpastes are formulated to taste good to kids. Adults should supervise tooth brushing by children under age six. Mouth-washes containing fluoride and prescription fluoride supplements should be kept out of the reach of children. A child who eats fluoridated toothpaste or drinks mouthwash should receive an immediate medical evaluation.

See also Calcium ; Infant nutrition ; Oral health and nutrition .


Buzalaf, Marília Afonso Rabelo. Fluoride and the Oral Environment. New York: Karger, 2011.

Connett, P. H., James S. Beck, and H. S. Micklem. The Case Against Fluoride: How Hazardous Waste Ended Up in Our Drinking Water and the Bad Science and Powerful Politics That Keep It There. White River Junction, VT: Chelsea Green, 2010.

Segrave, Kerry. America Brushes Up: The Use and Marketing of Toothpaste and Toothbrushes in the Twentieth Century. Jefferson, NC: McFarland, 2010.


Brody, Jane E. “Personal Health: Dental Exam Went Well? Thank Fluoride.” New York Times, January 24, 2012, D7.

Jagtap, Sneha, et al. “Fluoride in Drinking Water and Defluoridation of Water.” Chemical Reviews 112, no. 4 (April 2012): 2454–66.

Woolston, Chris. “The Healthy Skeptic: Keeping the Cavities Away with Fluoride-Free Toothpaste.” Los Angeles Times, February 6, 2012, E3.

Zimmerman, Jonathan. “Science Fights Fluoridation.” Los Angeles Times, November 16, 2011, A19.


American Dental Association. “Fluoride in Water.” http://www.ada.org/fluoride.aspx (accessed March 21, 2018).

Ly, Johnathan, and Richard D. Shin. “Fluoride Toxicity.” Medscape. Updated September 5, 2017. http://emedicine.medscape.com/article/814774-overview#showall (accessed March 21, 2018).

MedlinePlus. “Fluoride in Diet.” U.S. National Library of Medicine, National Institutes of Health. https://medlineplus.gov/ency/article/002420.htm (accessed March 21, 2018).


Academy of Nutrition and Dietetics, 120 South Riverside Plaza, Ste. 2000, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, http://www.eatright.org .

American Academy of Pediatric Dentistry, 211 East Chicago Avenue, Ste. 1700, Chicago, IL, 60611-2637, (312) 337-2169, Fax: (312) 337-6329, http://www.aapd.org .

American Dental Association, 211 East Chicago Ave., Chicago, IL, 60611-2678, (312) 440-2500, http://www.ada.org .

Tish Davidson, AM
Revised by Margaret Alic, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.