The reason why I think so is that the versions of proteins with heavy metals seem to be superior to those with the supposedly "correct" metal, as well as the heavy metal being extremely strongly preferred by the metabolism.

In the case of lead, it seems to be necessary for glucose transport, and seems to have effects similar to Rapamycin. It seems that Rapamycin basically only works by compensating for lead deficiency to some degree.

https://www.sciencedirect.com/science/article/abs/pii/S03784...