I found this link by a doctor on Charcoal and it's uses, I think you'll find this makes good reading. It seems good stuff to use

http://www.vrp.com/art/327.asp

Though it can interfere apparently with the absorption of some medications, so you have to be careful when you take it. Maybe you could take it a few days at a time, break and do it again? Just in case it interefers with some nutrient absorption also.

Other than that, it's harmelss and helpful.