Ironically, the healthiest people are the most likely to be deficient in iodine.
Why?
Healthy people tend to:
--Avoid iodized salt because of public health advice to limit sodium
--Use sea salt to obtain minerals like magnesium--but sea salt contains little iodine
--Limit meat--Carnivores obtain more iodine than vegetarians or vegans. In one study, up to 80% of vegans were iodine-deficient (Krajcovicova-Kudlackova M et al 2003).
--Exercise--Substantial amounts of iodine are lost through sweating. In a study of high school soccer players, 38.5% were severely iodine deficient, compared to 2% of sedentary students (Mao IF et al 2001).
That is indeed what I am seeing in my office, as well: The healthiest, most attentive to healthy eating, and most physically active are the ones showing up with small goiters (enlarged thyroid glands) and increased TSH and low free T4 levels.
Why am I checking thyroid and talking about iodine? Because even the smallest degree of thyroid dysfunction can double, triple, or quadruple your risk for cardiovascular events. See the posts Is normal TSH too high? and Thyroid perspective update.