Yeah, I just don’t see this happening across the whole population. Maybe with an expensive campaign to encourage yearly physicals you will get a certain sector of society; but there are going to be millions who haven’t got insurance, worry they would be wasting a doctor’s time, are scared of the authorities, can’t afford the travel time, and so on.

I believe there is a safe level. In Sweden the government recommends everybody to take 10 micrograms daily, with some groups at 20 micrograms, and this advice is very commonly followed. As far as I understand it that advice does an awful lot more good than it does harm.