Vitamin B12 (B12) is essential in the synthesis of all new cells and maintenance of myelin, a coating of the nerve pathways. B12 deficiency is a worldwide problem. A deficiency may result from inadequate intake, malabsorption or a genetic mutation. Depending on the study, 11 to 94% of vegetarians were reported as having a deficiency. Deficiency rates often exceed 50%. Two studies assessed B12 status among members of the Seventh-day Adventist Church. There was a 40% deficiency prevalence among the 25 vegans included in the first study. Similarly, close to 50% of vegans and close to one third of lacto-ovo-vegetarians, participants of the Adventist Health Study II, were reported as having a deficiency. About one-third of non-vegetarian Adventists also had B12 deficiency. Although a higher deficiency prevalence is usually reported among vegans, compared to other vegetarians, most studies found high deficiency prevalence in all vegetarians, regardless of other factors, such as demographic characteristics, place of residency, or age.