What else in our diet blocks iodine from the thyroid?
- Nitrates, thiocyanate and other compounds found naturally in everyday foods like broccoli, cauliflower, meats and leafy vegetables: 99%
- Perchlorate: less than 1%. Perchlorate is naturally found in organic fertilizer and in a variety of defense and industrial applications.
Source: Epidemiology of Environmental Perchlorate Exposure and Thyroid Function: A Comprehensive Review (Tarone, et al, June 2010)
In the human body at high doses, perchlorate can compete with iodine, which the thyroid gland uses to make hormones. This effect is called iodide uptake inhibition, or IUI, and this effect is not adverse. Notably, in its 2005 report, the National Research Council of the National Academies of Science (NAS) in the United States confirmed that IUI is not an adverse health effect, and that adverse effects of perchlorate exposure are only theoretical and have not been demonstrated in humans. There is little or no likelihood that dietary perchlorate intake could result in adverse health effects, since sufficient iodine intake reduces any effects perchlorate may have on the human thyroid. In its 2008 Total Diet Study, the FDA found that dietary iodine in the U.S. consistently exceeded current Estimated Average Requirements.
In December 2024, the European Food Safety Authority (EFSA) published an updated scientific opinion “concerning the public health risks associated with perchlorate in food.” As a result of EFSA’s review, EFSA has updated the TDI for perchlorate from 0.3 to 1.4 micrograms per kilogram of body weight per day (µg/kg-d). EFSA based its decision on new modeling that provided “greater prevision in evaluating the effects of different doses of perchlorate on individuals.” In addition, EFSA experts “provisionally concluded that at current levels of exposure there are no health risks for the general population.”
Read the EFSA’s Scientific Opinion
In its 2008 Total Diet Study, the FDA found that dietary iodine consistently exceeded current Estimated Average Requirements. That study also found that most perchlorate-containing foods contain relatively higher levels of iodine. The FDA does not recommend any changes to infants’ and children’s diets or eating habits based on current perchlorate data.
Explore FDA’s Questions and Answers »
The American Thyroid Association noted in a 2004 press release that it is highly unlikely the levels of perchlorate detected in foods have any measurable health effect.
Read the American Thyroid Association press release »
Of note, In 2024 Consumer Reports published a story on perchlorate and food which, despite finding the presence of perchlorate in low levels in some foods, came to the conclusion that “none of the foods tested had dangerous levels of perchlorate.” That should come as no surprise to anyone, as no “dangerous” level of perchlorate has ever been found in more than 70 years of research.
Read our Statement on the Consumer Reports Study