New research led by a public health expert at the University of Kent suggests water fluoridation in England is linked to higher rates of underactive thyroid.
Professor Stephen Peckham, of the University’s Centre for Health Service Studies, says a switch to other approaches to protecting tooth health should be considered.
The research team identified that water fluoridation above a certain level is linked to 30 per cent higher than expected rate of underactive thyroid in England.
After taking account of influential factors, such as gender and age, both of which are linked to increased risk of hypothyroidism, they found an association between rates of the condition and levels of fluoride in the drinking water. In areas with fluoride levels above 0.7mg/l, they found higher than expected rates of hypothyroidism than in areas with levels below this dilution.
High rates of hypothyroidism were at least 30% more likely in areas with fluoride levels in excess of 0.3mg/l.
In England, around 10% of the population (6 million) live in areas with a naturally or artificially fluoridated water supply of 1mg fluoride per litre of drinking water.
Professor Peckham said that research was ‘observational’, so no definitive conclusions should be drawn about cause and effect. He also emphasised that the researchers were not able to take account of other sources of fluoride, often found in dental products and food and drink.
But he pointed out that the findings echo those of previous research and that while they were only able to look at diagnosed hypothyroidism, there might also be other cases of impaired thyroid function that have not yet been diagnosed and treated.