Overdoing it is linked to something called the Wolff Chaikoff effect. It's definitely not good, and we ahould all be careful trying to follow a guide like this without a ND's help. That said... Given what I've learned this year, I'm very suspicious that the timing of the Wolff Chaikoff study was just a few years after fluoridated tap water waa introduced. I haven't had time to compare with the timing of brominated flame retardants or bromine disinfectants in hot tubs, etc