nutritional disorders
Vitamin B12 Deficiency
Etiology of Vitamin B12 Deficiency
Vitamin B12 deficiency can result from Inadequate intake Inadequate absorption Decreased utilization Use of certain drugs Inadequate vitamin B12 intakeis possible in vegans but is otherwise unlikely. Breastfed babies of vegan mothers may develop vitamin B12 deficiency by age 4 to 6 months because in these babies, liver stores (which are normally extensive in other babies) are limited and their rapid growth rate results in high demand. Inadequate vitamin B12 absorptionis the most common cause of deficiency (see table). In older people, inadequate absorption most commonly results from decreased acid secretion. In such cases, crystalline vitamin B12 (such as that available in vitamin supplements) can be absorbed, but food-bound vitamin B12 is not liberated and absorbed normally. Inadequate absorption may occur in blind loop syndrome (with Small Intestinal Bacterial Overgrowth (SIBO) ) or Vitamin B12 absorption may be inadequate if ileal absorptive sites are destroyed by Overview of Inflammatory Bowel Disease or are surgically removed. Less common causes of inadequate vitamin B12 absorption include Chronic Pancreatitis , gastric or Less commonly,decreased utilization of vitamin B12oruse of certain drugscauses vitamin B12 deficiency (see table). is often used synonymously with vitamin B12 deficiency. However, pernicious anemia specifically refers to anemia resulting from vitamin B12 deficiency caused by an Autoimmune Metaplastic Atrophic Gastritis with loss of intrinsic factor. Patients with classic pernicious anemia, most commonly younger adults, are at increased risk of stomach and other gastrointestinal cancers. 