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Iodine, fluoride and IQ

The correlation between iodine consumption and IQ is very strong. In this article you can read how iodine and other halogen substances affect IQ.

Iodine and fluoride

Iodine (I) is a chemical element that you have probably heard of before. This element is often added to table salt to ensure that people are getting enough of it. Iodine has a crucial function in proper brain development and functioning. In fact, a deficiency of this element is one of the biggest contributors to preventable brain damage in infants. Iodine deficiency by the mother during pregnancy causes severe cognitive impairment in the child, such as speech and hearing problems 1.

Nowadays a severe iodine deficiency is very rare as table salt and some common foods are often fortified with this element. We also have access to foods naturally rich in iodine such as fish, eggs and milk. Although there is enough iodine in our diet to prevent a clinical deficiency, some chemicals such as fluoride (F-) or perchlorate counteract the neuroprotective action of iodine.

Recently, the researcher Declan Timothy Waugh, published a very important study that explains the relationship between fluoride and iodine. Declan concludes that fluoride contributes to impaired iodine absorption and iodine deficiency disorders 2. Our bodies need more iodine to counteract the effect of toxic substances to which we are increasingly exposed, such as fluoride, perchlorate and flame retardants commonly sprayed on furniture and mattresses.

Iodine and IQ

To demonstrate the effect of iodine on brain development, a study in Malaga, Spain examined the IQ of 1221 children and their relative iodine levels. The study concluded that IQ was significantly higher in children who consumed iodized salt than in children who habitually consumed common or sea salt (not fortified). Thirty-eight percent of children who consumed dairy products at least three times a day had higher urinary iodine levels and higher IQs 3.

Fluoride and IQ

Regarding fluoride exposure, on the other hand, a study published in 2014 by “The Lancet,” one of the oldest and best-known general medical journals in the world, states that the observable increase in neurodevelopmental disabilities, including: autism, attention deficit disorder, hyperactivity and dyslexia, is caused by certain chemicals that damage the brain during development. The study describes that to neurotoxic substances already known for several years such as lead, methylmercury and arsenic, new ones such as manganese and fluoride have been added 4.

A meta-analysis conducted in 2012 determined that on average, children living in an area where fluoride is added to drinking water have an IQ 7 points lower than children less exposed to fluoride 5.

Iodine and fluoride counteract each other. On the one hand, sufficient iodine intake protects us against fluoride toxicity. On the other hand, fluoride inhibits iodine absorption. Depending on where you live, you may notice that both iodine and fluoride are added to fortified salt. Fluorine was known years ago for its anti-caries properties, but now this false science has been largely debunked. To the fortified salt in this case is added iodine, an essential element for neurodevelopment and for many other functions such as the production of thyroid hormones, and fluoride, a well known and studied neurotoxin. I therefore recommend using only a natural, unfortified salt and supplementing iodine separately.

The terms fluorine and fluoride can be confusing. Fluorine is the chemical element F found in the periodic table with atomic number 9. Fluoride is the same atom of fluorine but it has an extra electron. Therefore fluoride has a negative electric charge, in fact it is recognized with the symbol F- .

Supplementing with iodine

To minimize neurological problems and maximize well-being and IQ, it is necessary to reduce exposure to neurotoxins, including fluoride, and consume sufficient iodine.

Iodine supplementation needs an article in itself as iodine also mobilizes heavy metals and aids in their detoxification. Supplementing with significant amounts of iodine requires a certain intake of other elements that work synergistically with iodine, such as selenium.

In order to ensure sufficient iodine intake and protect against neurodevelopmental problems, however, it is sufficient to use a iodine supplement that provides a dose of less than 800 micrograms (ug or mcg) of potassium iodide.

The iodine supplement is extremely inexpensive and easy to take.

If you want more detailed information about iodine and its effects, I suggest you look at the scientific articles cited below.


  1. Choudhry, Hani, and Md Nasrullah. “Iodine consumption and cognitive performance: Confirmation of adequate consumption.” Food science & nutrition vol. 6,6 1341-1351. 1 Jun. 2018, doi:10.1002/fsn3.694 ↩︎

  2. Waugh, Declan Timothy. “Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health.” International journal of environmental research and public health vol. 16,6 1086. 26 Mar. 2019, doi:10.3390/ijerph16061086 ↩︎

  3. Piedad Santiago-Fernandez, Rosario Torres-Barahona, J. Antonio Muela-Martínez, Gemma Rojo-Martínez, Eduardo García-Fuentes, M. José Garriga, Ana García León, Federico Soriguer, Intelligence Quotient and Iodine Intake: A Cross-Sectional Study in Children, The Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 8, 1 August 2004, Pages 3851–3857, https://doi.org/10.1210/jc.2003-031652 ↩︎

  4. Grandjean P, Landrigan PJ. Neurobehavioural effects of developmental toxicity. Lancet Neurol. 2014 Mar;13(3):330-8. doi: 10.1016/S1474-4422(13)70278-3. Epub 2014 Feb 17. PMID: 24556010; PMCID: PMC4418502. ↩︎

  5. Choi, Anna L et al. “Developmental fluoride neurotoxicity: a systematic review and meta-analysis.” Environmental health perspectives vol. 120,10 (2012): 1362-8. doi:10.1289/ehp.1104912 ↩︎

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Last updated on Feb 01, 2022 20:32 +0100
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