Reference: Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. https://doi.org/10.17226/6015.
On top of the others’ comments on B12, it’s worth noting that there’s a common blanket recommendation for everyone over 50 to supplement B12, no matter their diet, because absorption gets worse with age. So it’s strange to insist on lack of B12 and need of medicine as a problem only for vegans.
Reference: Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. https://doi.org/10.17226/6015.