There’s a lot of fear surrounding the use of iodine (just as there is for vitamin A as retinol).
Wolff and Chaikoff discovered in 1948 that when the body is suddenly presented with large amounts of iodine, the thyroid shuts down.
Because of this study (which found its way into the medical literature quickly), doctors started warning people about taking and using iodine.
From this study:
By J. WOLFF,2 I. L. CHAIKOFF, R. C. GOLDBERG,3
AND J. R. MEIER
It was published in Endocrinology (http://press.endocrine.org/doi/pdf/10.1210/endo-45-5-504)
Volume 45 Issue 5 – November 1, 1949
Experiments designed to test the duration of inhibition, by excess iodide, on organic binding of Iodine in the thyroid gland are described. It is shown that the inhibitory action of excess Iodide on the normal rat thyroid is temporary in nature. Inhibition lasted for about 26 hours. Despite the continued maintenance of a high level of plasma total iodine (100-200 gamma per cent), the formation of significant amounts of organic iodine was resumed after 26 hours.
Received for publication August 30, 1949.
Because of the scare, the RDA is only 150 mcg. Studies have already shown that that is not sufficient to keep a body running at its best. It only enough to stafe off goiter. The need for iodine for the rest of the body is ignored. People are now so scared of iodine that, even though it is perfectly clear that the body needs more, they rather under dose than be healthy.