You can get too much of a good thing. A new study in the Journal of Pediatrics by Kara Connelly et al (including ICCIDD board member Elizabeth Pearce) found that three newborns whose mother ingested 12.5 mg of iodine daily -- 11 times the 1.1 mg daily upper tolerable level established by the WHO -- had, surprise! -- 10 times higher blood iodine levels than healthy control infants.

Excess iodine causes the thyroid to temporarily decrease function to protect against hyperthyroidism. Continuous excessive iodine exposure to the fetal and infant thyroid gland can cause long-term harmful effects on thyroid function.