(NaturalNews) The tables are finally starting to turn in regard to the perception that the world has of water fluoridation following the release of at least two reputable studies over the past three years documenting the adverse health effects caused by the chemical.Researchers from the University of Kent, a public research university based in the United Kingdom, conducted the latest and considerably groundbreaking study on the health effects potentially caused by adding fluoride to the public's water.After studying data obtained from nearly every medical practice in England, scientists found that fluoride may be increasing the risk for hypothyroidism, or an underactive thyroid, a condition in which the thyroid gland fails to produce enough hormones, resulting in symptoms such as fatigue, obesity and depression.Published in the, the study included the largest population ever analyzed in relation to the adverse health effects caused by water fluoridation.After collecting data from 99 percent of England's 8,020 general medical practices, researchers found that the locations with fluoridated water were 30 percent more likely to have high levels of hypothyroidism, compared to areas with low, natural levels of the chemical in the water.This means that up to 15,000 people could be suffering from depression, weight gain, fatigue and aching muscles, all of which could theoretically be prevented if fluoride were removed from the water, according to"Overall, there were 9 percent more cases of underactive thyroid in fluoridated places," reports , which also notes that 10 percent of England's water is fluoridated compared with nearly 70 percent of America's.The science paper also compared the fluoridated city of Birmingham with the city of Manchester, which refrains from fluoridating, and found that doctor's offices in Birmingham were nearly twice as likely to report high levels of hypothyroidism.The new report has some experts questioning their stance on water fluoridation "The study is an important one because it is large enough to detect differences of potential significance to the health of the population," said Trevor Sheldon, a medical researcher and dean of the Hill York Medical School who has published numerous studies in this field.Sheldon, who in the past supported fluoride , admits that the "case for general water fluoridation" is no longer clear.Released in March of last year, Public Health England's report states that "there is no evidence of harm to health in fluoridated areas," and no differences were found between fluoridated and non-fluoridated areas in regard to rates of hip fractures, osteosarcoma (a form of bone cancer), cancers overall, Down's syndrome births and all other recorded causes of death.New research, however, suggests that the spike in the number of cases of hypothyroidism in areas such as the West Midlands and the North East of England is "concerning for people living in those areas.""The difference between the West Midlands, which fluoridates, and Manchester, which doesn't was particularly striking. There were nearly double the number of cases in Manchester," said the study's lead author Stephen Peckham."Underactive thyroid is a particularly nasty thing to have and it can lead to other long term health problems. I do think councils need to think again about putting fluoride in the water. There are far safer ways to improve dental health."Hypothyroidism is particularly a cause for concern for women, as they're 15 times more likely than men to develop the condition. Previous studies suggest that fluoride inhibits the thyroid's ability to use iodine, which is an essential mineral for a healthy thyroid, the master gland in the human body.