Iodine is linked to brain and neural development,

so it’s not surprising it is also linked to IQ!

Iodine is commonly added to table salt in most

countries because some areas of the world would be deficient otherwise.

Interestingly, this article shows the trend in iodine supplementation and

how it is linked to IQ levels:

http://www.thejournal.ie/effects-of-iodine-salt-on-intelligence-mental-development-1013109-Aug2013/