I do understand what you are saying. (Most here in the good ol' U.S.of A. are also highly potassium and magnesium deficient, too). I guess I should have commented more on "I wonder how studies and diagnoses would come across with a group of people who were actually NOT deficient in ANYthing!"
You might find this interesting, though:
Back over 100 years ago doctors found Iodine supplementation SO helpful for SO many things that they had a saying:
"If ye don't know where, what and why
Prescribe ye then K and I"