Fluoride
Description
Fluoride is most concentrated within tissues such as cementum, bone, dentin, and enamel. Fluoride is the ionic form of fluorine, and is instrumental in protecting bone and tooth enamel from loss of constituent minerals.
Fluoridated water is the most abundant and important source of fluoride for humans, and has been proven to aid in the reduced incidence of dental caries.
Excessive fluoridation of teeth has resulted in a condition called mottled enamel, which is characterized by discolored enamel. Extremely high fluoride intake has been known to result in death.
Inconclusive evidence has linked fluoride to such phenomena as enhanced iron absorption and increased wound-healing rate.
Method of Action
Fluoride is proposed to enhance the precipitation of hydroxyapatite crystals in solutions of calcium and phosphate (e.g., blood) and therefore tends to prevent the demineralization of bone and teeth.
It has been further proposed fluoride becomes integrated within the hydroxyapatite crystals, creating enlarged and less soluble crystals. Because these crystals are less soluble and less reactive, dissolution of the tooth structure by acidic by-products of microorganism metabolism cannot occur as readily. Bone is also less likely to demineralize due to the decreased solubility of the fluoride containing crystals.
The action of fluoride on hydroxyapatite crystals in bone and teeth make it a probable aid in the prevention of dental caries and various bone demineralization disorders, such as osteoporosis, osteomalacia, and periodontal disease.
Plasma fluoride levels stay relatively constant, even in times of low fluoride consumption, due to the availability of fluoride from bones. Fluoride absorption is very efficient and occurs primarily in the stomach. Fluoride treatments for teeth are most effective if the fluoride comes into direct contact with the teeth, as is the case with fluoridated water and toothpaste.
Excretion occurs primarily through the urine and sweat.
Properties & Uses
Fluoride intake throughout life has been cited as beneficial in reducing the prevalence of senile osteoporosis. High levels of fluoride intake have been used therapeutically in the treatment of osteoporosis.
Water fluoride concentrations of one part per million have resulted in a decrease in the incidence of dental caries of up to 70%, as well as large decreases in the incidence of periodontal disease.
Although it has not been proven conclusively, fluoride may increase the rate of wound healing and enhance iron absorption.
Consequence of Deficiency
Fluoride deficiencies result in an increased incidence of dental caries, increased incidence of osteoporosis, and less stable bone and tooth structure overall.
Low fluoride consumption has been linked to a higher incidence of calcification of the abdominal aorta artery.
Because fluoride inhibits the solubility of minerals, such as calcium in the bone, low fluoride intake also results in a higher incidence of bone resorption of the jaw, which is known as periodontal disease.
Toxicity Factors
Fluoride can be toxic, but only in amounts far in excess of normal dietary consumption. One part per million fluoride (or one milligram per liter of water) is added to fluoridated water supplies. Concentrations of two to eight parts per million may result in mottled enamel, or dental fluorosis. These disorders result in a discoloration of enamel. Concentrations of 8 to 20 parts per million can result in osteosclerosis. At concentrations of 2,500 times the recommended daily allowance death can occur.
Acute fluoride toxicity is very rare, with less than 500 cases recorded up to 1970. Mottled tooth enamel occurs when excess fluoride added to water supplies, but the problem is only aesthetic in nature. Prolonged excess fluoride exposure (more than 20 milligrams daily for 20 or more years) can lead to crippling skeletal fluorosis; this is extremely rare.
Under experimental conditions, high levels of fluoride have been associated with higher calcium retention and interference of collagen formation, with possible inhibition of normal growth.
Recommended Dietary Allowance
| RDA for adults: | 1.5 - 4.0 mg |
| RDA for child/adolescent: | 1.5 - 4.0 mg |
| RDA for age 0-1: | 0.1 - 1.0 mg |
| RDA for age 1-3: | 0.5 - 1.5 mg |
The above is 1980 values for RDA.
For over thirty years, Recommended Daily Amounts has existed in the United Kingdom. It has been used to measure the adequacy of an individual's diet. However, in 1991 the Committee on Medical Aspects of Food Policy (COMA) gave forth a whole new set of figures upon the request of the Department of Health's Chief Medical Officer. Reference Nutrient Intake (RNI) is one of these sets collectively known as "Dietary Reference Values." RNI is an amount of a nutrient that is enough for almost every individuals, even someone who has high needs for the nutrient. This level of intake is, therefore, considerably higher than what most people would need. If individuals are consuming the RNI of a nutrient they are most unlikely to be deficient in that nutrient.
Food Sources
| Buckwheat | Coffee |
| Fish | Fluoridated water |
| Lettuce | Onion |
| Red wine | Rice |
| Soybean | Spinach |
| Tea - black | White wine |
References
Czanarin, Doris, M. 1984. Minerals - Food, Nutrition and Diet Therapy. M.V. Krause and L.K. Mahan. W.B. Saunders Co, Phila
Goodhart, Robert S. & Maurice E. Shills. Modern Nutrition In Health And Disease. 6th edition. Philadelphia: Lea and Febiger, 1973.
Guthrie, Helen A. Introductory Nutrition. 5th edition. St. Louis: C.V. Mosby Co., 1971.
Hegsted, M.D. 1976. Present Knowledge In Nutrition. 4th ed. The Nutrition Foundation Pub., Washington D.C. 605.
Krause, M.V. & L.K. Mahan. 1979. Food, Nutrition and Diet Therapy. 6th ed. W.B. Saunders Company, Philadelphia. 963 pp.
Pfeiffer, Carl D., M.D. Mental And Elemental Nutrients. New Canaan, Conn.: Keats Publishing, 1975.
Recommended Dietary Allowances. 9th ed. 1980. Ntnl Acad of Sci. Wash.D.C.
Walji, Hasnain. 1992. The Vitamin Guide-Essential Nutrients for Healthy Living, Element Books, Dorset .U.K.
Walji, Hasnain. 1994. Vitamins, Minerals and Dietary Supplements - A definitive Guide to Healthy Eating . Hodder Headline Plc. London.
Williams, Sue Rodwell. Nutrition And Diet Therapy. 5th edition. St Louis: Times Mirror Mosby, 1985.
Wilson, Eva D., et al. Principles Of Nutrition. 4th edition. New York: John Wiley & Sons, 1979.
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