- Study found high levels of fluoride in water is linked to hypothyroidism
- Condition is where thyroid gland fails to produce key hormones
- A sufferer is therefore likely to gain weight, suffer depression and tiredness
- Scientists urge change in public health policy, which promotes water fluoridation to boost the nation's tooth health
- Public Health England dismissed findings and said 'decades of research... shows no association with reduced thyroid function' and fluoride
Weight gain and depression caused by an underactive thyroid is linked to high levels of fluoride in the water supply, scientists have claimed.
A study published today has revealed water fluoridation above a certain level is linked to 30 per cent higher than expected rates of hypothyroidism in England.
The findings have prompted researchers to call for a revision of public health policy, which currently encourages the fluoridation of water to protect the nation's tooth health.
Fluoride is a naturally occurring mineral found in water, and certain foods including tea and fish.
Its main benefit is in helping reduce the risk of tooth decay.
As a result the mineral is added to many brands of toothpaste, and in some areas, to the water supply.
But researchers at the University of Kent have warned the mineral may be responsible for triggering underactive thyroids.
Other experts have however, disagreed with their findings, arguing the research methods were flawed.
Public Health England also dismissed the study, adding 'decades of research tells us that water fluoridation is a safe and effective public health measure, and shows no association with reduced thyroid function'.
Also known as hypothyroidism, the condition prevents the thyroid - a gland in the neck - producing vital hormones.
That in turn, promotes weight gain, causes depression and tiredness in sufferers.
The authors, led by Professor Stephen Peckham, at the university's Centre for Health Service Studies, conclude: 'Consideration needs to be given to reducing fluoride exposure, and public dental health interventions should stop [those] reliant on ingested fluoride and switch to topical fluoride-based and non-fluoride-based interventions.'