In the July issue of the American Journal of Clinical Nutrition, German researchers tracked 174 apparently healthy people living in Germany and the Netherlands.
They found that 92% of the vegans they studied -- those who ate the strictest vegetarian diet, which shuns all animal products, including milk and eggs -- had vitamin B12 deficiency.
That article refers to this study that states:
Of the 3 groups, the vegans had the lowest vitamin B-12 status. In subjects who did not consume vitamins, low holotranscobalamin II (< 35 pmol/L) was found in 11% of the omnivores, 77% of the LV-LOV group, and 92% of the vegans.
This other study says:
Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life.
Are the vast majority of Vegans Vitamin B12 deficient?