Water Fluoridation and Our Thyroid
The February 26, 2015 Chicago Tribune article , “British Study Links Fluoride, Underactive Thyroid”, discussed the recent study linking fluoridated water to higher rates of hypothyroidism. The article included comments from the American Dental Association spokesman, Dr. Edmond Hewlett, who claimed that “the 2006 report by the U.S. National Research Council found no adverse effects on the thyroid even at levels more than four times greater than that used in fluoridation.”
In fact, in 2006 the National Research Council found that ingesting .05 mg/ kg/day or more of fluoride depresses levels of thyroid hormone (.03 mg/kg/ day for the 15% of Americans with inadequate iodine intake).1 For a healthy 120-pound female, this is the amount of fluoride in 2. 7 liters of fluoridated water (1.6 liters of fluoridated water if iodine deficient). Considering that fluoridated water not only is drunk from the tap, but also is consumed in all beverages and foods prepared with tap water (sodas, sports drinks, beer, wine, soups, processed foods, etc.), many women in this country receive enough fluoride to affect their thyroid gland’s function. And, we all receive additional fluoride from fluoridated toothpaste, dental varnishes, and fluoride-based pesticides on foods.
One in eight women in our country will develop thyroid disease, including hypothyroidism, thyroid cancer and Grave’s Disease. Thyroid cancer is one of our most rapidly-increasing cancers. We know there is a strong correlation between thyroid disease and exposure to environmental toxins . From the NRC data, we also know that many women are ingesting more than enough fluoride to impact their thyroid function.
For the ADA to state that ”currently, the best available scientific evidence indicates that optimally fluoridated water does not have an adverse effect on the thyroid gland or its function" not only is inaccurate, it disregards the health of the 20 million people in our country living with thyroid disease, as well as those who are yet-undiagnosed. For a dentist to “take issue” with a study showing a significant correlation between fluoridated water and hypothyroidism is medically naive.
While fluoride once was seen as a silver bullet for tooth decay, targeting only the teeth, we now know that its effects on one’s body are far-reaching. In addition to the thyroid gland, fluoride has recently been placed on the EPA’s list of developmental neurotoxins, alongside lead and mercury, as a chemical with the potential to negatively affect an infant’s developing brain.2 3
The recent science of fluoride demands that doctors, as well as dentists, shape the debate about water fluoridation.
--- Angela C. Hind, M.D.
1 National Research Council, Fluoride in Drinking Water A Scientific Review of EPA’s Standards, at 262 (The National Academies Press 2006).
2 Grandjean, P. et al., “Neurobehavioural Effects of Developmental Toxicity,” The Lancet Neurology , Volume 13 , Issue 3 , 330 – 338 (March 2014).
3Mundy, W., et al., “Building a Database of Developmental Neurotoxicants: Evidence from Human and
Animal Studies,” available at http://www.epa.gov/ncct/toxcast/files/summit/48P%20Mundy%20TDAS.pdf (March 2009).