Our family (the Irish side) has a bit of a history of pernicious anaemia, which I understand as being connected to inability to absorb Vitamin B12. My grandmother was made to eat raw liver (which actually I adore, being a bit weird!) but it did no good.
I do think that vegetarians/vegans ought to be aware of the problems caused by deficiencies of essential minerals, vitamins and nutrients.
My niece won't take any supplements derived from animal products though, which I respect.