“too much iodine” is subjective. Average dosage in Japan is 50 mg/day. I take 100mg/day. Many people I know take mor than that. You will excrete all excess iodine in the urine. You need much higher doses than the US RDA.
Brownstein claims that average healthy Japanese consume 13 mg of iodine daily via their seafood rich diet.
There is laboratory proof and history of SOME that should not have too much: http://www.thefreelibrary.com/Use+of+Iodine+for+Water+Disinfection%3a+Iodine+Toxicity+and+Maximum...-a066354878 I do not know of any facts of medical science that have conclusive evidence that taking X20 or more times the RDA does anything for you positive. There is evidence that taking too much (and this number will vary according to the individual) for 2-3 weeks can cause harm. Balance in all things.