Fluorine (F) – Source, Absorption, RDA, Deficiency, Controversy
Fluoride occurs naturally in the earth’s crust, water and food as a negatively charged ion of the element fluorine.
Fluoride is considered to be a trace element because only small amounts are present in the body (about 2.6 grams in adults), and because the daily requirement for dental health is only a few milligrams per day.
About 99% of the body’s total fluoride is found in bones and teeth [source]. Although its role in preventing dental caries (tooth decay) is widely established, fluoride is not generally considered an essential mineral because people do not require it for growth or to stay alive.
However, if one considers the prevention of chronic disease (dental caries) an important criterion in determining necessity, then fluoride is properly considered an essential trace mineral.
Fluoride Food sources
The fluoride content of most foods is low (less than 0.05 mg/100g) and can vary from place to place because the mineral content of soil varies geographically.
Rich sources of fluoride include tea, which accumulates fluoride in its leaves, and marine fish eaten with their bones (e.g., sardines).
Foods made with mechanically separated (deboned) chicken, canned meats, hot dogs and baby food also add fluoride to the diet.
Foods generally contribute 0.3-0.6 mg of daily fluoride intake. An adult male living in a fluoridated community has an intake range of 1-3 mg/day. The intake is less than 1 mg/day in non-fluoridated areas.
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Fluoride Absorption
Soluble fluoride is largely absorbed by the human body. The bioavailability of fluoride in solid foods is reduced and reaches up to 50-80%.
Also fluoride bound to proteins is even less absorbed. In general, most of the fluoride in food or ingested water is rapidly introduced into the bloodstream through the digestive tract.
However, the amount introduced into the bloodstream also depends on factors such as how much fluoride is consumed and how well fluoride dissolves in water.
Factors such as age and health status affect what happens to the fluoride ion once it is in your body.
After it is introduced into the body, about half of the fluoride leaves the body quickly in the urine, usually within 24 hours, unless large amounts are ingested (20 mg or more, which is the amount in 20 or more liters of optimally fluoridated water).
Most of the fluoride ion that remains in the body is stored in the bones and teeth.
Interactions with other nutrients
Calcium, magnesium and chlorine appear to interact with fluoride and reduce its absorption and use, while phosphorus and Sulphur increase its bioavailability.
- Chloride (salt) – a diet low in chloride salt has been found to increase fluoride retention by reducing urinary excretion of fluoride.
The following food components have been found to inhibit fluoride absorption:
- Calcium – forms insoluble formations with fluoride and is able to significantly reduce fluoride absorption when found in the same meal. However, absorption of fluoride in the form of monofluorophosphorus (unlike sodium fluoride) is unaffected by calcium.
- Magnesium – forms insoluble formations with fluoride and is capable of significantly reducing fluoride absorption when present in the same meal.
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Body Functions
The main action of fluoride is the mineralization of bones and teeth. Fluoride is absorbed in the stomach and small intestine. When it enters the bloodstream, it quickly enters the tissue with minerals (bones and growing teeth).
At normal levels of consumption, fluoride does not accumulate in soft tissue. The predominant minerals in bone are calcium and phosphate crystals, known as hydroxyapatite crystals.
Fluoride’s small radius and high chemical activity allow it to either displace the larger hydroxyl ion (- OH) in the hydroxyapatite crystal, forming the fluorapatite, or increase the density of the crystal by entering the spaces within the hydroxyapatite crystals. Fluoroapatite hardens tooth enamel and stabilizes the metallic elements of the bones.
Recommended Daily Allowance (RDA)
In 1997, the US Food and Nutrition Board set values for adequate amounts of fluoride, implying that it is a beneficial but not essential nutrient.
The above values refer to the intakes of fluoride (from all sources) required for the maximum reduction in the incidence of caries without causing side effects.
Fluoride Deficiency
In animal experiments, fluoride deficiency leads to reduced growth, infertility and anemia. There is no evidence of identical symptoms in humans.
Inadequate fluoride consumption has just one evident effect: an increased risk of dental caries (tooth decay) in people of all ages.
Adequate intake also appears to maintain the integrity of skeletal tissue. It is precisely for this reason that fluoride is considered an essential trace element.
Fluoride Toxicity
Fluoride is harmful in large doses, hence concentrated fluoride products should be handled and stored with caution to avoid the risk of severe fluoride intoxication, especially in children and other sensitive people.
5 mg/kg body weight is considered the lowest amount that might produce life-threatening effects.
Acute fluoride toxicosis is nearly often accompanied by nausea, abdominal discomfort, and vomiting.
Diarrhea, profuse saliva and tears, sweating, and overall weakness are also possible symptoms.
Dental fluorosis
Small opaque white spots or markings on the enamel of the teeth characterize the milder type of dental fluorosis, which may only be detected by a professional observer.
Spots and mild staining of the teeth characterize moderate dental fluorosis, while staining and disintegration of the teeth characterize severe dental fluorosis.
When dental fluorosis affects the incisors and canines in moderate to severe forms, it becomes a cosmetic problem (front teeth).
Excessive fluoride ingestion before the first permanent teeth emerge causes dental fluorosis (generally before 8 years of age).
It’s also a dose-dependent problem, with larger fluoride doses linked to more dramatic tooth impacts.
Fluoride intakes 2-3 times the recommended level for children of a sensitive age appear to considerably raise the risk of mild to moderate dental fluorosis, but severe dental fluorosis has only been documented at fluoride intakes 5 times the recommended amount.
Mild and moderate dental fluorosis has become more common in the last 50 years, owing primarily to increased fluoride consumption via toothpaste, however improper usage of fluoride supplements may also play a role.
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Water Fluoridization
According to the US Centers for Disease Control and Prevention (CDC), water fluoridation was one of the 10 most valuable public health measures of the 20th century, particularly for protecting teeth.
Over time, fluoride began to be added to commercial products such as toothpastes and mouthwashes, and fluoride products such as tablets, drops and gels were created for professional use.
The outer substance of the teeth, the enamel, is ‘wet’ and daily loses trace elements and regains them by two processes known as demineralization and plating respectively. Oral bacteria create acids that destroy enamel and the underlying tooth material dentin, resulting in dental caries.
The fluoride present in saliva is concentrated in the plaque that forms on the teeth, preventing the acids from acting on the teeth’s trace elements. It also stimulates the plating of the teeth by sticking to their surfaces and attracting to them the calcium ions contained in the saliva.
👉 In the United States, the optimal fluoride content in drinking water for preventing dental cavities has been defined at 0,7-1,2 mg per liter.
Fluoride Controversy
Water fluoridation has been hotly contested and has been blamed, among other things, for a host of health side effects – from heart disease and cancer to Down’s syndrome, AIDS, allergies, Alzheimer’s disease, mental retardation, osteoporosis and fractures.
Another issue of controversy concerns safety from chemicals used to fluoridate water.
Fluoride as a Neurotoxin
In 2014 a study published in the Lancet Neurology journal implicated fluoride as a neurotoxin. This was a meta-analysis of 27 studies related to young children’s exposure to fluoride through drinking water.
The conclusion was a seven-point drop in children’s IQs due to fluoride. Worse still, in most cases the fluoride levels did not exceed the recommended amounts. It should be noted that fluoride causes neurotoxicity in laboratory animals, negatively affecting their learning and memory.
Fluoride and Hypothyroidism
Another study published in 2015 in the Journal of Epidemiology & Community Health found that water fluoridation above a certain level was associated with a 30% higher rate of hypothyroidism in England but blamed flawed methodology.
The debate around potential side effects has not reached a definitive conclusion.
Fluoride not to be given to infants
It should be noted that some experts do not recommend giving fluoride to infants under 6 months of age (the American Food and Nutrition Council considers 0.01 mg to be sufficient).
They also recommend that artificial milk should be produced from non-fluoridated water, and that children under 2 years of age should not brush their teeth with fluoride toothpaste.
From 2 to 6 years of age, moreover, they should brush with such toothpastes under supervision to ensure that they do not swallow them.
Potential Carcinogen
Since 1990, fluoride has been listed as a potential carcinogen by the US National Cancer Institute with evidence of bone cancer and osteosarcoma [source].
The International Academy of Oral Medicine and Toxicology has classified fluoride as an unacceptable dental drug due to its high toxicity.
Research has shown that if a child consumes 50ml of fluoride-containing toothpaste, they can die.
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