Fluoride and Thyroid: Can Fluoride in Your Drinking Water Cause Thyroid Problems?

January 16th, 2013

According to the American Thyroid Association, more than 12 percent of Americans will develop a thyroid condition in their lifetime. Many Americans feel that this rate is higher than expected and that perhaps not only genetics are to blame. A quick search on the internet reveals many websites suggesting that fluoride, an additive in many community water systems, may be partially responsible for thyroid problems. Since January is Thyroid Awareness Month, it seems worthwhile to investigate whether fluoride affects the functioning of the thyroid.

What is the Thyroid?

The Thyroid Gland

The thyroid is a gland located in the middle of your lower neck, in front of your trachea (windpipe). Though it is small, the thyroid affects the major functions of your body by releasing the hormones, triiodothyronine (T3) and thyroxine (T4). The thyroid gland uses iodine from your food to produce T3 and T4. These hormones affect growth and development, body temperature, and metabolism. T3 and T4 are necessary for brain development in infants and children as well.

Research Results

Studies of how fluoride may affect thyroid functioning have been ongoing since the early 1900s. In 2006, the National Research Council (NRC) released a report that reviews many studies about fluoride and thyroid problems. Numerous experiments have been performed on animals with varying results. While some did not show any effect of fluoride on thyroid functioning, a few studies of rats and mice showed decreased thyroid hormone levels and increased goiter development (swelling of the gland) at higher fluoride intake levels. The intake levels varied with each study. One interesting fact that was mentioned in a few of the studies was that high fluoride levels intensified the effects of the test subjects that were iodine-deficient. Remember that, as mentioned previously,  iodine is necessary to produce the thyroid hormones.

The NRC report also mentioned several studies that examined thyroid hormone levels in children in other countries with high fluoride levels in the drinking water. The conclusions of these studies were similar to several of the animal studies in that the scientists speculated that high fluoride levels may cause greater effects in low-iodine situations.

A Word of Caution

It is important to not rush to any conclusions about fluoride and thyroid issues. As the NRC mentions in the report, there are many inconsistencies in the studies that make them difficult to compare. The studies vary in:  1) types of test subjects used, 2) test concentrations of fluoride, 3) the types of measurements taken, such as hormone levels and occurrence of goiters, and 4) the types of effects observed. Scientists are not even certain how fluoride affects the thyroid gland. One theory that fluoride competes with iodide has been disproven. Clearly, more research is needed in this area.

Takeaway Message

Though the EPA has set limits for fluoride in drinking water, it is not known how much fluoride is necessary to cause effects in humans. If you already have a thyroid condition or are iodine-deficient, you might want to consult your doctor about limiting your exposure to fluoride. Visit the blog about Drinking Water Quality to learn about how you can discover how much fluoride is added to your drinking water.

 


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