Fluoride could be causing depression and weight gain and councils should stop adding it to drinking water to prevent tooth decay, scientists have warned.
A study of 98 per cent of GP practices in England found that high rates of underactive thyroid were 30 per cent more likely in areas of the greatest fluoridation.
It could mean that up to 15,000 people are suffering needlessly from thyroid problems which can cause depression, weight gain, fatigue and aching muscles.
Last year Public Health England released a report saying fluoride was a ‘safe and effective’ way of improving dental health.
But new research from the University of Kent suggests that there is a spike in the number of cases of underactive thyroid in high fluoride areas such as the West Midlands and the North East of England.
Lead author Professor Stephen Peckham, Centre for Health Service Studies, said: “I think it is concerning for people living in those areas.