Alkaline phosphatase, an enzyme involved in bone growth and liver function, may also be affected by low level fluoride intake.

According to scientists from the University of California at San Diego, fluoride switches off the enzyme cytochrome C oxidase, an oxygen carrying respiratory enzyme; deficiencies of this vital enzyme have been linked to cancer, severe diseases and even cot death (J Biol Chem, 1984; 259: 12984-88).

It's also been shown by research at Kings College in London that fluoride forms very strong hydrogen bonds with amides, which are formed when amino acids join together to form a protein (J Am Chem Soc, 1981; 103: 24-8). This can cause chromosomal damage. If the protein is distorted, the body's immune system no longer recognises it, treats it as a foreign protein and will try to destroy it, which in turn triggers allergic skin or gastrointestinal reactions (J Yiamou-yannis, Fluoride: The Aging Factor, Delaware, Ohio: Health Action Press, 1993: 94-9).

Stomach and bowel disorders are the main features of fluoride intolerance. Even small amounts of fluoride can form hydrofluoric acid in the stomach to produce gastric pains, nausea and vomiting. Young children are particularly at risk. Fluoride tablets can even cause gastric haemorrhages; in one instance, a 9 year old boy sustained such damage that large parts of his stomach had to be removed (Fluoride, 1977; 10: 149-51).

Links with thyroid disease

The most readily identifiable feature of soft tissue fluorosis is extraordinary general fatigue, which is frequently linked to thyroid deficiency. The thyroid gland requires iodine to produce the hormone thyroxine, which controls the rate of metabolism in the body. But when fluorine is present, iodine is displaced, which will cause a thyroid gland to stop working properly (K Roholm, Handbuch Experi-menteller Pharma-kologie, Ergaenzung-swerk, Vol 7, Berlin: Springer, 1938: 20).

The parathyroid gland, which regulates the distribution of calcium and phosphorus in the body, is extremely sensitive to excessive amounts of fluoride. Over 50 years ago, Indian doctors found a close relationship between skeletal fluorosis and hyperparathyroidism (J Hyg 1942; 42: 500-4).

Fluoride has even been shown to affect the pituitary gland, which controls growth rate by regulating the production of thyroid hormones (Seances Soc Biol Fil, 1930; 103: 981-2). In animals, less than normal amounts of thyroid hormones are produced when animals are given water containing a fluoride content equivalent to that of water fluoridation (Bull Schweiz Akad Med Wiss, 1954; 10: 211-20).

Professor A K Susheela of the Fluoride and Fluorosis Research Foundation of India, a consultant to the Indian government, has published over 100 scientific papers on the hazards of fluoride. Using scanning electron microscope photography, she has proved that when exposed to fluoride, red blood cells are killed prematurely, lowering haemoglobin and causing anaemia. She also showed that calcium levels diminish as fluoride levels in the body rise; the gastrointestinal tract mucosa is damaged, causing irritable bowel syndrome; and blood fluoride levels rise continuously with prolonged use of fluoridated toothpaste.

When people are bombarded with fluoride, in the form of fluoridated water, toothpaste and mouth rinses, muscles and elements of connective tissue, particularly collagen fibre and bone tissue, undergo degenerative changes, says Prof Susheela.