Adding fluoride to the public water supply should be stopped, say researchers. Any supposed benefits of preventing tooth decay are more than outweighed by the increased risk of causing thyroid problems, leading to fatigue, depression and weight gain.
High rates of underactive thyroid-or hypothyroidism-are 30 per cent more likely in areas that have been fluoridated, say researchers who have surveyed 98 per cent of GP practices across the UK.
This suggests that around 15,000 people now have thyroid problems simply because their local water supply has been fluoridated, say researchers from the University of Kent. Areas of the West Midlands and the North-East of England-where many local authorities have started fluoridating the water-are especially affected.
Lead researcher Prof Stephen Peckham said: "The difference between the West Midlands, which fluoridates, and Manchester, which doesn't, was striking. There was nearly double the number of cases (of hypothyroidism) in the West Midlands".
The researchers compared areas of fluoridation against health records from 7,935 GP practices around the UK. Rates of hypothyroidism were at least 30 per cent more likely in practices with fluoride levels in excess of 0.3mg/l.
Previous studies have shown that fluoride inhibits the body's iodine levels, which are essential for a healthy thyroid. The thyroid gland regulates the body's metabolism, and an underactive gland can lead to depression, weight gain, fatigue and aching muscles.
(Source: BMJ Journal of Epidemiology and Community Health, 2015; doi: 10.1136/jech-2014-204971)