That's not true of iodine. Iodine deficiency has been quite common; it's why salt is artificially supplemented with the element. Natural occurring trace iodine in salt and food, unlike with bromine, is often not enough. For this reason the hypothesis that iodine is needed biologically goes all the way back to 1851.
https://en.wikipedia.org/wiki/Iodised_salt
"Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of intellectual and developmental disabilities."