Fluorine
Functions
Most of the minerals in the bones such as calcium and phosphate exist as hydroxyapatite crystals. Some of the hydroxy l portions are replaced with fluoride to form fluorapatite. This is more acid-resistant and so protects teeth against decay. Fluoride seems to act at various stages of the tooth-plaque-salvia system. It has an antibacterial effect in the plaque. Fluoride also inhibits demineralisation and enhances mineralisation. Therefore fluoride is important in the structure of the enamel as well as having a topical role at reducing dental decay.
The role of fluoride in bone is unclear, with some suggesting that it may make bone stronger. Early research suggested that osteoporosis was more common in areas where the water was low in fluoride compared to high fluoride areas. More recent research however, suggests that the administration of fluoride may be detrimental to bones.
Although it is recognised that fluorine in the form of fluoride is beneficial in terms of dental health, fluorine has not yet been accepted as an essential trace element.
Recommended Intakes
Although as yet there is no established physiological requirement for fluorine, most health organisations recommend a water supply in the range of 0.7-1.0 parts per million (ppm).
A suggested range of safe and adequate intakes for adults of 1.5-4.0mg/day is recommended (RNI=4mg/day for males, 3mg/day for females), with a range of 1.5-2.5mg/day for children and 0.1-1.0mg/day during the first year of life.
The UK recommend that intakes of fluoride up to 0.22mg/kg/day for infants up to 6 months is safe. For infants and children up to 6 years, an intake of 0.12mg/kg/day is recommended as safe. Intakes of 0.05mg/kg/day are recommended as safe for children over 6 years and adults.
Food Sources
Beverages are the major source of fluoride with their contribution depending on the concentration of fluoride in water. Tea is also a rich source of fluorine.
Foods contain trace amounts of fluorine. The amount in processed foods depends on the fluoride content of water used in the processing in the home or commercially.
Deficiency
Low fluoride intakes increase susceptibility to tooth decay.
Toxicity
The range between exposure to too much and too little fluorine is narrow.
When too much fluorine is ingested in the first few years of life, fluorosis (discolouration) of teeth can occur. This may occur due to the liberal use of fluoride tablets and/or toothpastes which can contain 1000ppm fluoride. Young children can be at risk if they swallow too much toothpaste.
Chronic high intakes of fluorine can affect the skeleton, causing dense bones and joint abnormalities. Skeletal fluorosis is known to occur in India, China, and South Africa.
When large doses have been administered for the treatment of oestoporosis, the resulting bone quality tends to be poor which may cause more fractures.
Symptoms of acute fluoride poisoning include nausea, vomiting, abdominal pain, and numbness of the face and extremities.
Water Fluoridation
It is widely agreed that the fluoridation of water to a level of 1parts per million (ppm) has no known adverse health effects. | 
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