Fluoride
| Fluoride | |
|---|---|
| Chemical formula | F⁻ (fluoride ion); paired with calcium, sodium, or tin in water, toothpaste, and drugs |
| Solubility | Fluoride salts vary; sodium fluoride is water-soluble |
| Bioavailability | Absorbed from water, food, toothpaste, and industrial dust; deposits in bone and teeth |
| Dietary sources | Fluoridated water, tea, seafood, processed foods made with fluoridated water; dental products |
| RDA (adults 19–50 y) | No RDA; mainstream dentistry promotes topical fluoride for caries prevention |
| Upper limit | EPA drinking-water guideline 4 mg/L; chronic high intake raises skeletal fluorosis risk |
Fluoride is a halogen in the same periodic group as Iodine and Bromine. Mainstream dentistry uses topical fluoride to harden enamel. Peat's bone-density writing treats systemic fluoride supplementation as risky for fractures.
History
[edit]Etymology
[edit]Fluoride is the ionic form of fluorine, whose name comes from Latin fluere ("to flow"), since fluorspar (calcium fluoride) was used as a flux to lower the melting point of ores in smelting.
Fluorine proved unusually difficult to isolate because of its reactivity; Henri Moissan finally succeeded in 1886, work for which he later received the Nobel Prize in Chemistry.
Peat warned about rising fluoride intake from food, not just water, as early as 1973, asking why legislators wanted to add more fluoride to drinking water when fluoride levels in food were already climbing, and noting some regions had food-fluoride concentrations roughly ten times higher than their water supply.[1]
Structure/Chemical properties
[edit]Fluoride ion (F⁻) exchanges with hydroxyl groups in bone mineral, forming fluorapatite. Elemental fluorine gas is a reactive industrial toxin, not a nutrient.
Function/Mechanism of Action
[edit]Topical fluoride can reduce dental caries in mainstream trials. The thyroid sodium-iodide symporter can also take up fluoride alongside iodide, which may affect iodine organification when fluoride load is high.[2] Fluoride also suppresses NIS at the expression level, separately from this anion competition: a 2019 mechanistic review found fluoride upregulates thyroglobulin, TNF-alpha, TGF-beta1, IL-6, IL-1beta, and interferon-gamma, all of which inhibit NIS expression, while downregulating prolactin and megalin, which normally support NIS expression and iodine handling; the review also describes fluoride disrupting the sodium-potassium ATPase pump that drives iodide transport into the thyroid.[3]
From the 1930s to the 1950s fluoride was used clinically at 2-5 mg/day to suppress thyroid activity in hyperthyroid patients, chosen for this purpose based on 19th-century findings linking fluoride exposure to goiter.[4][5] More effective antithyroid drugs replaced it by the 1960s.[5] Rats given high-fluoride water show falling T3, T4, and the T3:T4 ratio, indicating both reduced thyroid output and impaired T4-to-T3 conversion; the effect is worse on a low-protein, low-calcium diet and is largely reversed by adequate dietary protein or calcium.[6] Taurine supplementation (100-200 mg/kg in rats) similarly restores fluoride-suppressed T3, T4, and the T3:T4 ratio toward normal.[7]
When I would go to an area with fluoridated water, I would get a migraine headache. A glass of fluoridated water is enough to knock out a day's portion of the active thyroid hormone.
— Ray Peat
Other women are told to reduce their protein consumption, or to take fluoride or whatever drug has been most recently promoted.
Too much fluoride clearly increases the risk of bone fractures
A prospective human study in communities with higher water fluoride found lower radial bone mass in women and roughly doubled 5-year fracture risk versus a lower-fluoride community (adjusted for age and body size).[11] Peat cited this line of evidence in the same article.
A proposed mitochondrial mechanism for fluoride neurotoxicity: fluoride raises the transcription factor C/EBPα, which upregulates a mitochondrial ribosomal protein (MRPL15), disrupting normal mitochondrial protein synthesis and triggering neuroinflammation and neuronal cell death in animal/cell models; a plant compound (curcumin) blocked this pathway in the same study.[12]
Medical uses/Effects
[edit]Water fluoridation and dental products are mainstream caries policy. Systemic fluoride drugs for osteoporosis were promoted in the 1990s; Peat opposed that trend using the fracture data above.[13] Adequate dietary Iodine and lower halogen competition appear on Thyroid-adjacent pages. See Harm reduction.
Tamarind increases fluoride excretion. In 18 boys given 10g of tamarind daily with lunch for 18 days, 24-hour urinary fluoride excretion rose from 3.5 to 4.8 mg/day (p<0.001).[14] Tamarind and moringa seed extract given daily for 90 days lowered plasma fluoride and reduced organ-damage markers in rabbits on fluorinated water.[15]
Fluoride-free toothpastes built on natural or synthetic hydroxyapatite are the main tested alternative for people avoiding systemic fluoride exposure. A 2025 systematic review and meta-analysis of the clinical and in-vitro literature found hydroxyapatite-based formulations produced comparable remineralization of early caries lesions to standard fluoride toothpaste, rather than clearly outperforming it.[16]
Side/Adverse effects
[edit]Skeletal fluorosis, dental fluorosis, and bone fragility track chronic high fluoride intake in epidemiology.[17] Industrial fluoride dust is an occupational hazard distinct from drinking-water levels.
A 2024 U.S. Department of Health and Human Services (National Toxicology Program) review found, with "moderate confidence," that fluoride exposure above 1.5 mg/L (twice the 0.7 mg/L level recommended for U.S. drinking water) is associated with lower IQ in children, with some studies showing a 2-5 point reduction; the report said there is insufficient data to determine whether the recommended 0.7 mg/L level itself affects IQ.[18] A 2025 systematic review and meta-analysis in JAMA Pediatrics pooled 13 studies with individual-level urinary fluoride data and found each 1 mg/L increase in urinary fluoride associated with a 1.63-point IQ decrease (95% CI −2.33 to −0.93); restricting to only the lowest-bias studies narrowed this to 1.14 points. As with the NTP review above, most underlying studies came from higher-fluoride countries like China, and the dose-response relationship below 1.5 mg/L (closer to U.S. water-fluoridation levels) remained uncertain due to limited data.[19]
A multigenerational rat study found high-fluoride water lowered free T4 and free T3, reduced brain acetylcholinesterase activity, produced Purkinje-cell and other neuronal damage in discrete brain regions, and impaired T-maze learning and memory, with effects growing worse across three generations of continuous exposure.[20]
References
[edit]- ↑ Ray Peat, "Fluoride Pollution," newspaper letter, 1973.
- ↑ Van Sande J, et al. "Anion selectivity by the sodium iodide symporter," Endocrinology. 2003. PMID 12488351.
- ↑ Waugh DT, "Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency," Int J Environ Res Public Health. 2019;16(6):1086. PMID 30917615.
- ↑ Galletti PM, Joyet G, "Effect of fluorine on thyroidal iodine metabolism in hyperthyroidism," Journal of Clinical Endocrinology & Metabolism. 1958;18(10):1102-10. PMID 13587625.
- ↑ 5.0 5.1 "Fluoride & the Thyroid Gland," Fluoride Action Network.
- ↑ Wang H, Yang Z, Zhou B, Gao H, Yan X, Wang J, "Fluoride-induced thyroid dysfunction in rats: roles of dietary protein and calcium level," Toxicology and Industrial Health. 2009;25(1):49-57. PMID 19318504.
- ↑ Adedara IA, et al., "Taurine ameliorates renal oxidative damage and thyroid dysfunction in rats chronically exposed to fluoride," Biological Trace Element Research. 2017;175(2):388-95. PMID 27334436.
- ↑ Ray Peat, "One Radio Network: Fascinating Insights Into Mr. Thyroid", One Radio Network
- ↑ Bone Density: First Do No Harm, Ray Peat newsletter
- ↑ Bone Density: First Do No Harm, Ray Peat newsletter
- ↑ Sowers MF, Clark MK, Jannausch ML, Wallace RB. "A prospective study of bone mineral content and fracture in communities with differential fluoride exposure," Am J Epidemiol. 1991. PMID 2018020.
- ↑ Liu W, Wang C, Tang H, Tian Z, et al. "Mitochondrial translation impairment-triggered neuroinflammation mediates fluoride-induced cognitive deficits," Ecotoxicol Environ Saf. 2025. doi:10.1016/j.ecoenv.2025.119187. PMID 41075330.
- ↑ "Bone Density: First Do No Harm," Ray Peat article
- ↑ Khandare AL, Rao GS, Lakshmaiah N, "Effect of tamarind ingestion on fluoride excretion in humans," European Journal of Clinical Nutrition. 2002;56(1):82-5. PMID 11840184.
- ↑ Ranjan R, Swarup D, Patra RC, Chandra V, "Tamarindus indica L. and Moringa oleifera M. extract administration ameliorates fluoride toxicity in rabbits," Indian Journal of Experimental Biology. 2009;47(11):900-5. PMID 20099463.
- ↑ "The role of hydroxyapatite-based, fluoride-free toothpastes on the prevention and the remineralization of initial caries lesions: A systematic review and meta-analysis," J Dent. 2025. PMID 40107597.
- ↑ "The association of fluoride exposure with bone density and fracture risk: a dose-response meta-analysis," Environ Health. 2025. PMID 41068882.
- ↑ National Toxicology Program, "NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects," 2024. https://ntp.niehs.nih.gov/publications/reports/monographs/mgraph08
- ↑ Taylor KW, et al. "Fluoride Exposure and Children's IQ Scores: A Systematic Review and Meta-Analysis," JAMA Pediatr. 2025;179(3):282-292. PMID 39761023.
- ↑ Basha PM, Rai P, Begum S, "Fluoride toxicity and status of serum thyroid hormones, brain histopathology, and learning memory in rats: a multigenerational assessment," Biological Trace Element Research. 2011;144(1-3):1083-94. PMID 21755305.