MOST of us put our trust in fluoride to help prevent tooth decay. It is a common ingredient in toothpaste and mouthwashes, and several countries, including large parts of the UK, add fluoride to the water supply.

Just last month, a study was published which reported that adding fluoride to table salt had reduced dental decay in Jamaica.

However, not all scientists are enthusiastic about fluoride. Recent evidence suggests it is not as effective in preventing tooth decay as was originally thought. In fact, it is believed fluoride treatment has the capacity to cause dental disease.

There is also some evidence that fluoride may increase the risk of other health issues, including weakened bones and thyroid conditions. So could adding fluoride to drinking water be doing us more harm than good?

Fluoride is a by-product of certain manufacturing practices (primarily the phosphate fertiliser industry). Precisely what lay behind the decision to add it to water supplies is not clear. Fluoride is, after all, a potentially toxic waste product. When fluoridation of water started 60 years ago, there was no good evidence to suggest that fluoride might prevent tooth decay.

However, partly as a result of later studies which suggested it might have tooth-protecting qualities, fluoridation of water became accepted practice.

More recently, the British government commissioned a review of the scientific literafluorideture on this subject, the results of which were published last year in the British Medical Journal. The York study concluded that the rationale behind the fluoridation of water is based on weak scientific evidence.

In addition, it found that the protection offered by fluoride is much less than previously thought: just one in six people drinking fluoridated water benefits from it.

Other studies show similarly poor results. In the largest dental health survey ever conducted in the U.S., fluoridation of water was found to protect less than 1 per cent of the total tooth surfaces in a child’s mouth.

Studies conducted in Finland, East Germany, Cuba and Canada have found that the rate of dental decay does not increase when communities stop fluoridation.

And while the benefits of fluoride appear to have been overrated, it seems that the hazards of this substance have been downplayed.

For instance, the York study found that almost 50 per cent of individuals drinking fluoridated water exhibit a condition known as ‘dental fluorosis’ – a mottling of the teeth thought to be caused by the toxic effects of fluoride.

So, while fluoridation of water may prevent dental disease in about 15 per cent of the population, it seems to cause dental disease in about half those treated.

And if toxic effects are seen in the teeth, what damage may be done in the rest of the body?

The authors of the York study said they could find no real evidence for the toxic effects of on the body, but other studies claim fluoride has the capacity to weaken bones and increase the risk of fracture.

There is also evidence that fluoride can accumulate in the pineal gland in the brain. Potentially, this could disrupt a range of body processes, including sleep.

FLUORIDE is also known to reduce the function of the thyroid gland (responsible for regulating the speed of the metabolism), and studies in animals show fluoride may bring on premature puberty.

Another question is the ethics of fluoridation. If fluoride does indeed reduce dental decay, should it not be classed as a medicine? If this is the case, then individuals who live in areas where the water is fluoridated are essentially being medicated without their consent.

When doctors prescribe drugs, we generally do so knowing the patient’s sex, age, weight, medical history and current drug therapy.

They will judge whether a treatment is necessary, decide on an appropriate dosage and monitor the effects. None of this is true in the case of water fluoridation.

Ireland is the most heavily fluoridated country. About threequarters of its water supply is treated with the chemical.

While the Irish have generally good dental health, studies show lower dental disease in nonfluoridated areas such as Wales and Scotland. In England, fluoridation depends on where you live.

Steps can be taken to reduce exposure to fluoride. Those living in a fluoridated region can avoid drinking tap water or filter their water.

For those wanting to avoid fluoride in toothpaste, many natural alternatives exist.

One particular brand based on aloe vera (called AloeDent) comes in several forms, one of which contains vitamin K which has been shown to be effective in preventing tooth decay. AloeDent can be found in health food stores.