for a discussion of research on B-12 levels in natural hygienists and living-fooders, see: http://www.beyondveg.com/billings-t/comp-anat/comp-anat-7b.shtml The same research is also discussed in a long paper by Jack Norris of Vegan Outreach at: http://www.veganoutreach.org/health/b12.html Tom Billings