Fluoride: Does it affect the thyroid?

I have heard that fluoride in toothpaste and water adversely affects the function of the thyroid. Do you think there is any truth in this?

Dr Fred Kavalier answers your health question:

Fluoride in high doses can effect the functioning of the thyroid gland, but the amount of fluoride in water and toothpaste will not have any significant effect. In 2000 a review of the scientific literature on water fluoridation was carried out by the NHS Centre for Reviews and Dissemination at York University. They concluded that there was no reputable scientific evidence to support the idea that water fluoridation caused thyroid problems. Too much fluoride can cause a discolouration of the tooth enamel – dental fluorosis – but unless you are ingesting excessive amounts of fluoride, I would not worry about your thyroid gland.

Readers write

A flurry of letters take issue with my suggestion that the amount of fluoride in toothpaste and water will have no significant effect on the thyroid gland.

AW writes: "Fluoride has been found to accumulate in high concentration around pipe bends, valves and in sediment. It is also present in pesticides, in industrial pollution and in many medical drugs. We may all be receiving more fluoride than is thought."

PC from New York, director of a fluoride action group, says: "You are clearly out of date on the literature. Since the York Review was published in 2000, there has been a considerable discussion on the impact of fluoride on the thyroid gland and other parts of the endocrine system."

Please send your questions and suggestions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax 020-7005 2182 or e-mail to health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions.