Fluoride in water is 'linked to thyroid problem.

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.

Source  - Daily Mail