The water supplied to around 10% of the English population is high in fluoride (around 1 mg per litre) as a result of either artificial addition or natural occurrence. Fluoride improves dental health by combating tooth decay, making the enamel more resistant to bacteria, and last year Public Health England released a report saying it was ‘safe and effective’.
However research this week from the University of Kent, published in the BMJ’s Journal of Epidemiology and Community Health, suggests that high fluoride levels could lead to an increased risk of Hypothyroidism- an underactive thyroid. This is also supported by previous studies which have shown that fluoride inhibits iodine production- vital for a healthy thyroid.
The thyroid gland is found in the neck below the thyroid cartilage (which forms the Adam’s apple) and regulates the metabolism by controlling how sensitive the body is to hormones. Hypothyroidism can lead to symptoms such as depression, fatigue and weight gain, and affects fifteen times more women than men.
Analysis of data from 7935 of the General Practitioners in England, which includes around 95% of the English population, revealed that areas with fluoride levels in excess of 0.3 mg per litre were 30% more likely to have hypothyroidism. The researchers also exposed that the West Midlands, where water is fluoridated, had around double the rates of hypothyroidism than Manchester, where water is not fluoridated.
The lead author, Stephen Peckham, says the data is “concerning to the 10 % of the population living in high fluoride areas.”
On the other hand, other scientists do point out that the observed association could just be a consequence of other factors in the fluoridated areas. Similarly, the Public Health England director insists that the fluoride is safe and that their previous research has not revealed any association with reduced thyroid function.