A recent study out of England has found a link between the amount of fluoride in public drinking water and a rise in incidence of hypothyroidism (underactive thyroid). The study, published in the Journal of Epidemiology & Community Health, compared 2012 national data on levels of fluoride in drinking water to trends for hypothyroidism as diagnosed by family physicians across England.
The thyroid is a butterfly-shaped gland near the base of the neck that produces hormones. Thyroid hormones control the rate of many body activities, including how fast calories are burned and how fast the heart beats. If the thyroid gland isn’t active enough, it does not make enough thyroid hormone to meet the body’s needs.
The research found that in areas where tap water fluoride levels exceeded 0.3 milligrams per liter, the risk for having an underactive thyroid rose by 30%. The study, led by Stephen Peckham of the University of Kent in Canterbury, England found that hypothyroidism rates were nearly double in urbanized regions that had fluoridated tap water, compared with regions that did not.
Fluoride is added to water to prevent tooth decay. According to the American Dental Association, studies show that community water fluoridation prevents at least 25% of tooth decay in children and adults throughout the lifespan even though fluoride is widely available as a topical ingredient in toothpaste and mouthwash.
The British researchers say that although fluoridation of the water supply may be important for dental health, studies have also shown that iodine deficiency that may be caused by extra ingestion of fluoride is related to hypothyroidism.
In the US alone, there are over 15 million people affected by hypothyroidism, where water is fluoridated.
“Consideration needs to be given to reducing fluoride exposure,” the researchers wrote. They believe that public efforts to strengthen dental health should move away from fluoridated water and instead “switch to topical fluoride-based and non-fluoride-based interventions.”
Fluoridation of water is also a controversial topic because fluoride has been shown to be a developmental neurotoxin, and the amount of water people drink varies widely.
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