Fluoride
mineralA trace mineral essential for tooth enamel strength and cavity prevention.
Definition
A trace mineral essential for tooth enamel strength and cavity prevention. Added to drinking water in many countries at 0.7mg/L. DV is 4mg. Also found in tea and seafood.
What Is Fluoride?
Fluoride is the ionic form of the element fluorine and is considered a beneficial trace mineral, though its classification as strictly "essential" remains debated since life can be sustained without it. The adult body contains approximately 2.6 grams of fluoride, with over 99 percent incorporated into bones and teeth as fluorapatite, a more stable and acid-resistant form of the mineral compared to hydroxyapatite. Fluoride's well-documented role in dental health has made water fluoridation one of the most impactful public health interventions of the 20th century.
Key Functions
- Dental caries prevention: Fluoride inhibits bacterial acid production in plaque, promotes remineralization of early enamel lesions, and is incorporated into enamel and dentin during tooth development, making them more resistant to acid dissolution. Both systemic fluoride (ingested during tooth development) and topical fluoride (toothpaste, rinses, gels) provide protection.
- Bone strength: Fluoride stimulates osteoblast proliferation and bone formation. High-dose fluoride (once used therapeutically for osteoporosis) increased bone mineral density, though the resulting bone was more brittle — illustrating the narrow therapeutic window for this mineral.
Dietary Reference Values and Sources
The AI for fluoride is 4 mg/day for men and 3 mg/day for women. The UL is 10 mg/day. Community water fluoridation in the US is maintained at 0.7 mg/L (parts per million). Major sources include:
- Fluoridated drinking water (1 L): ~0.7 mg
- Grape juice (1 cup): ~0.05-0.6 mg
- Raisins (3.5 oz): ~0.23 mg
- Cooked crab (3 oz): ~0.21 mg
- Wine: variable (0.04-0.3 mg per glass)
- Black tea (1 cup): ~0.1-0.5 mg
Fluorosis: Excessive Fluoride
Dental fluorosis occurs when excessive fluoride is ingested during the period of tooth enamel formation (birth to approximately age 8 in permanent teeth). Mild fluorosis appears as white spots or streaks on enamel; severe fluorosis causes brown staining and pitting. Skeletal fluorosis — painful bone and joint problems — results from very high chronic fluoride exposure (above 10 mg/day for many years), typically from naturally fluoride-rich groundwater in certain parts of the world (India, China, Africa) rather than from properly fluoridated water supplies.