Okay I just reread the OP and want to revise my evaluation. (The first time I read it was a few hours ago during work.) It's not clear whether the issue was junk food veganism or an absorption problem. MD's have very little knowledge about vegan dieting so it could have just been 1 or 2 minerals out of check that were causing a lot of harm. I don't mean to make the OP sound stupid and I actually do support non-vegan alternatives for those who cannot do it in a healthy matter. Hopefully in the future this will be synthesized meat that's chemically identical to the animal flesh.
I do have some issues with the original poster's evaluation of ethics, like thinking that something that's necessary can't be bad. There's a whole bunch of terrible logic but that's beside the point.
The last thing I want to clarify is why I'm on this site if I would normally be suspicious of it. If you want a "curezone" that actually works try WebMD, though even that's no replacement for an MD. I was here just reading the OP because of a google search on a different sub-topic of food health and ethics and just noticed that someone was planning on cheating against the doctor's orders on a life-threatening treatment. Please take these words to heart, and again ask on Facebook or search me up on Skype (markuswoltjer) if you have any questions or doubts. I won't login here again most likely.