Everything's unhealthy if you have too much of it, pretty much everything is essential in small enough quantities. Look at cobalt - it's lethally poisonous at s

Everything's unhealthy if you have too much of it, pretty much everything is essential in small enough quantities. Look at cobalt - it's lethally poisonous at surprisingly low levels, fairly unpleasant long before that, and even in its non-radioactive form it causes cancer. But it's also a trace element that shows up in vitamin B12, and without cobalt all your myelin falls off your nerves and you die.