I learned it from a report from a doctor from Germany, posted on the 'net about five years ago. It's in the Amalgam Support Forum , and on the doctor's blog- he's a toxocology expert. ALA can do the same thing, since it is capable of carrying mercury both out AND in. The circulatory system isn't quite so discriminant with nutrients, at least in the case of halides- it's why the rest period in chelation is so important, so that you are not stirring up the toxins TOO much for too long. You also have to keep red bloodcell production high. The good news is that almost every antioxidant helps carry mercury out to the liver, and success with chelation cleanup is a very reachable goal! a lot of folk do it.
From what I've read on dental cleanup during chelation. it's very important to have selenium available in supplement form for when the chelation gives a mental health crisis- generally negative emotions, snappiness, crankiness, anger- it's a sign of mineral deposits running low, and selenium helps mellow out the pit there. Chelation with drug-chelators like DMSA and EDTA up the excretion of many more minerals than mercury alone, which is why in many places on these forums, folk on chelation patterns are told to stay high on mineral-rich foods and other ways to re-mineralize the body, like the Sea Salt s.