Fluorine, as fluoride, is found in the earth's crust in combination with other minerals, and is also part of seawater. Fluoride is available naturally in the diet as calcium and sodium fluoride. It is sodium fluoride that is added to the drinking water of many cities.

Fluorine is a constituent of bones and teeth, but since it is very seldom added to supplements, we have not identified a large volume of data on this element.

In some areas, fluoride ion is added to drinking water (in very low concentrations) since it renders tooth enamel relatively immune to bacteriological attack. It does this by replacing the OH group of hydroxyapatite with fluoride. In other areas, fluoride is not added to water, despite its proposed benefits, as a consequence of protests from civil rights activists who object to the addition of anything to water.

Fluoride has no known function other than strengthening teeth and bones which a subject of debate in recent years. About half of ingested fluoride, about 3 mg. per day, is eliminated through the kidneys and a little more through perspiration. The remainder is stored mainly in the bones.

Signs of deficiency: Excessive tooth decay, osteoporosis. Excess calcium, aluminum and fat lower fluorine absorption.

Symptoms of high intake and signs of toxicity: teeth stained with mottled spots (known as dental fluorosis), stomach cramps, pain, faintness, vomiting, diarrhea, black stools, shallow breathing, tremors, increased saliva, deformed teeth and bones, osteomalacia. Fluorine can disrupt body's ability to use vitamins, retard growth, calcification of tendons and ligaments, can damage reproductive organs, adrenal glands, CNS, brain, kidneys, heart.

There is some evidence that it is effective in the treatment of osteoporosis, as an increase in the retention of calcium was noted, together with a reduction of bone demineralization, by some people treated with fluorine salts.