https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-national-evil https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-nati... is a pretty good article d

https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-national-evil https://www.lrb.co.uk/the-paper/v45/n23/jonah-goodman/a-nati... is a pretty good article describing how a Swiss doctor showed experimentally that adding iodine was a cure for goitre and the associated mental handicaps (Switzerland is highly deficient in iodine in many areas, because glaciers in the last ice age removed most top soil).