Scientists in the UK are stressing the need to switch to an alternative approach in efforts to combat tooth decay after results of a study that was recently published in the Journal of Epidemiology & Community Health suggest fluoridation has negative health effects.

According to the study, fluoride in drinking water is associated with a 30% increased risk of hypothyroidism (underactive thyroid) in England, prompting the research team to question public health policies relating to water fluoridation as a tool to protect the public's dental health.

Roughly 10% of the English population, amounting to some 6 million people, reside in areas that receive drinking water that either contains natural fluoride or is artificially fluoridated with 1mg fluoride per liter of water.

The scientists examined data supplied by the Drinking Water Inspectorate to assess fluoride levels in drinking water supplies by area for 2012. They then compared this data set with data relating to underactive thyroid diagnoses obtained from family doctors in 2012-2013. They obtained complete data from 7935 out of 8020 general family practitioners.

The research team also conducted a secondary analysis, where they compared two urban areas: West Midlands, whose drinking water supplies are fluoridated; and Greater Manchester, whose drinking water supplies are not treated with fluoride.

After taking influential factors, such as older age and female sex -- both linked to a higher risk of underactive thyroid -- into account, the researchers found that there was a link between the level of fluoride in drinking water and higher rates of hypothyroidism.

In areas where fluoride levels where higher than 0.7 mg/l, rates of underactive thyroid where higher than expected compared to areas where fluoride levels were lower than this. In areas where drinking water contained fluoride at levels higher than 0.3mg/l, doctors saw at least a 30% increase in hypothyroidism cases. Furthermore, incidents of hypothyroidism were almost twice as common in the West Midlands compared to Greater Manchester.

The researchers acknowledge that this was purely an observational study, and as they did not take other sources of fluoride, such as those found in toothpaste and other products, into account, no conclusive statements relating to cause and effect can be made. However, they stress that these results echo the findings of previous studies, and while they only assessed diagnosed cases, there are likely to be other undiagnosed cases that they missed.

"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," the researchers conclude.

If you are concerned about the health impacts of fluoride in your drinking water, you can take steps to remove fluoride with a drinking water filter that is capable of removing fluoride. The Berkey range of filters that accommodate filters in the bottom housing can be fitted with fluoride cartridges that will remove fluoride and arsenic from your drinking water, making it safe for your family to drink.

Journal Reference

S Peckham, D Lowery, S Spencer. Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. Journal of Epidemiology & Community Health, February 2015 DOI: 10.1136/jech-2014-204971