Can you guess the number one prescribed medication in the USA between 2013-2014? It was for under-active thyroid! The CDC and USPHS is shooting for 75% of the population to be drinking Fluoridated tap water.
A large study that looked at data from nearly every general medical practice in England suggests that water fluoridation may increase the risk of developing hypothyroidism, or underactive thyroid. This condition, in which the thyroid gland doesn’t produce enough hormones, is associated with symptoms such as fatigue, obesity and depression.
The study found that locations with fluoridated water supplies were more than 30 percent more likely to have high levels of hypothyroidism, compared to areas with low levels of the chemical in the water. Overall, there were 9 percent more cases of underactive thyroid in fluoridated places.
Fluoride is added to the water of about 10 percent of England’s population—and to the taps of about two-thirds of Americans—for the purpose of preventing cavities. It has proved controversial ever since being adopted by American public health authorities in the 1950s, and then spreading to some other countries; supporters say it is a boon for dental health, while critics say it may lead to a variety of health problems.
The paper, published today in the Journal of Epidemiology & Community Health, also directly compared the fluoridated city of Birmingham with the city of Manchester, which doesn’t add the substance to the water. After controlling for factors such as sex and age (women are more likely than men to have the condition, and the elderly more likely than the young), the researchers concluded that doctor’s offices in Birmingham were nearly twice as likely to report high levels hypothyroidism, says study co-author Stephen Peckham, a researcher at the University of Kent.
“It raises a red flag,” says Dr. Philippe Grandjean, an environmental health researcher and physician at Harvard University, “that possible interference with thyroid function needs serious consideration when regulating fluoride levels in drinking water.”
The findings are all the more important since this is the “largest population ever studied in regard to adverse effects of elevated fluoride exposure,” says Grandjean, who wasn’t involved in the study. Data was collected from 99 percent of England’s 8,020 general medical practices, and the study found that a total of 3.2 percent of the population had hypothyroidism, a 14 percent increase from 2008.
“The study is an important one because it is large enough to detect differences of potential significance to the health of the population,” says Trevor Sheldon, a medical researcher and dean of the Hull York Medical School. Sheldon, who has authored numerous studies in this field, no longer thinks (as he once did) that the “case for general water fluoridation” is clear.
Considering the comprehensiveness of this study—it covered nearly the whole of England—regional differences in fluoride intake or other confounding factors are unlikely to have played a role in the striking results, says Kathleen Thiessen, a senior scientist at the Oak Ridge Center for Risk Analysis, a company that does human health risk assessments for a variety of environmental contaminants.
But John Warren, a professor and researcher in the department of dentistry at the University of Iowa, disagrees. He points out that the study merely shows correlation, not causation. It also “assumes that since one group lives in a fluoridated community, they have higher exposure to [the substance] than those in the non-fluoridated area,” he says. This is significant flaw, he says—to draw a valid connection between fluoride and hypothyroidism, you’d have to measure individual exposure to the chemical and show that those with the condition had higher levels of exposure.