The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature
Thus, with few exceptions, the reviewed studies documented relatively high deficiency prevalence among vegetarians.
Vegans who do not ingest vitamin B12 supplements were found to be at especially high risk. Vegetarians,
especially vegans, should give strong consideration to the use of vitamin B12 supplements to ensure adequate vitamin B12 intake. Vegetarians, regardless of the type of vegetarian diet they adhere to, should be screened for vitamin B12 deficiency