http://www.positivehealth.com/PERMIT/ARTICLES/Dentist/drage44.htm

it says...
Quote:
A word here about vitamin B12. It has been found to be a ‘methylator’, instantly converting the mercury ions into methyl mercury. Avoid vitamin B12 when detoxifying, although the other B supplements are not a problem.

I also found....
Quote:
Vitamins can pose problems, too: Vitamin B12, cobalamin, greatly accelerates the absorption of mercury in the tissues.

And that one is from....
http://www.chebucto.ns.ca/Health/Nsaeha/fall96dental.html