disorders of nutrition
Vitamin B12 Deficiency
Causes of Vitamin B12 Deficiency
Vitamin B12 deficiency can result when the following occur: People do not consume enough vitamin B12. The body does not absorb or store enough of the vitamin. Vitamin B12 deficiency develops in people who do not consume any animal products (vegans) unless they take supplements. If a vegan mother breastfeeds her infant, the infant is at risk of vitamin B12 deficiency. Deficiency due to inadequate consumption is unlikely in other people. The most common cause of vitamin B12 deficiency is inadequate absorption. The following can cause absorption to be inadequate: Small Intestinal Bacterial Overgrowth (SIBO) in part of the small intestine Impaired absorption Overview of Malabsorption such as celiac disease or certain pancreatic disorders) Overview of Inflammatory Bowel Disease (IBD) affecting the last part of the small intestine Tapeworm Infection None Human Immunodeficiency Virus (HIV) Infection None Metabolic and Bariatric Surgery for weight loss Surgery that removes the part of the small intestine where vitamin B12 is absorbed (used to treat Medication Treatment of Diabetes Mellitus ) Repeated exposure to nitrous oxide (laughing gas) Lack of intrinsic factor Decreased stomach acidity (common among older people) Intrinsic factor may be lacking because abnormal antibodies, produced by an overactive immune system, attack and destroy the stomach cells that produce intrinsic factor—an autoimmune reaction called autoimmune metaplastic atrophic gastritis. Intrinsic factor may also be lacking because the part of the stomach where intrinsic factor is produced was surgically removed. Vitamin B12 deficiency due to lack of intrinsic factor causes a type of anemia called pernicious anemia. Among older people, absorption may be inadequate because stomach acidity is decreased. Decreased stomach acidity reduces the body’s ability to remove vitamin B12 from the protein in meat. However, the vitamin B12 found in vitamin supplements can continue to be well absorbed even in people with decreased stomach acid. Overview of Liver Disease may interfere with the storage of vitamin B12 because most of the body's vitamin B12 is stored in the liver. 