The debate has long raged on about whether adding fluoride to drinking water is a boost or a bane. The US Centers for Disease Control has dubbed water fluoridation one of the ten greatest public health achievements of the 20th century, due to its cavity-reducing properties and measurable improvement of the nation's dental health. (Numerous 15-year studies have shown that drinking fluoridated water reduces tooth decay in children by an average of about 60 percent.)
But countless groups have spoken out in opposition to the practice since fluoridation became common practice in the 1940s. Citizens and advocacy groups alike have questioned not only whether fluoride is effective and safe (fluoride poisoning can result in weakened bones, and adverse reactions such as nausea, vomiting, and diarrhea), but also whether it's ethical to medicate the water supply of entire nations. Though water fluoridation continues in many countries such as the US, the United Kingdom, Ireland, Canada, and Australia, many others—including Germany, Sweden, Japan, the Netherlands, and Finland—have discontinued it.
A new study will add fuel to the ongoing fire of controversy surrounding the practice. Researchers at the University of Kent analyzed data from nearly 8,000 general practitioners' offices in the UK—accounting for 98 percent of practices. They found that patients in areas with high levels of fluoride in the water (equal to or greater than 0.3 milligrams per liter) are 30 percent more likely to have underactive thyroids. According to the research team, up to 15,000 British citizens could be experiencing hypothyroidism due to fluoride exposure. Common symptoms of an underactive thyroid include weight gain, depression, low body temperature, and fatigue.
The key to a healthy thyroid is iodine, which is generally absorbed through the blood and stored and regulated by the body in the thyroid gland. (Iodine-rich food sources include seafood, dairy products, eggs, seaweed, and iodized salt.) But because fluoride is more electronegative than iodine, it displaces it in the body, disrupting thyroid function and subsequently impacting hormone levels that keep metabolism in check. Numerous studies (including one from just last year) have previously confirmed fluoride's ability to promote and exacerbate iodine deficiency, but the University of Kent study is one of the first to identify causation.
After releasing the report, the team of researchers urged public health officials to reexamine the practice of water fluoridation, despite a report from Public Health England released last year that aimed to assure its safety. Currently, about 6 million Britons—mainly in the Eastern part of England—continue to receive water with added fluoride, and another half a million live in areas with naturally high levels of fluoride in the water supply.
The researchers noted the correlation with hyperthyroidism starting at fluoride levels of 0.3 milligrams per liter. In 2010, the US Department of Health and Human Services asked a team of scientists to reassess the acceptable level of fluoride for domestic drinking water supplies, resulting in a recommended change from up to 1.2 milligrams per liter to just 0.7 milligrams per liter, though up to 4 milligrams per liter is technically permitted.
Was Dr. Strangelove's maniacal General Ripper right all along when he asked, "Do you realize that fluoridation is the most monstrously conceived and dangerous Communist plot we have ever had to face?"
Communist plot … maybe not. But since there are already enough other things in the world that could make us fat and depressed, maybe we should take a closer look at this one.