Vitamin B-12 deficiencies caused by dietary shortfalls are rare in the United States because B-12 is readily available in the meat, eggs and dairy products that are common in the American diet. In some cases, however, gastric disorders can interfere with your ability to absorb nutrients from the foods you eat. A number of medical disorders are known to affect B-12 absorption.
Pernicious Anemia
Pernicious anemia occurs when you lack an enzyme called intrinsic factor that enables your intestines to absorb vitamin B-12. This disorder is believed to be caused by an autoimmune response that destroys the cells responsible for secreting intrinsic factor. About 2 percent of adults over the age of 60 have pernicious anemia, according to the Office of Dietary Supplements. Pernicious anemia generally requires lifelong supplementation with B-12 injections, or high dosages of oral B-12.
Atrophic Gastritis
Up to 30 percent of those older than 60 experience decreased B-12 absorption due to atrophic gastritis, according to the Linus Pauling Institute at Oregon State University. This condition occurs when the stomach's ability to secrete hydrochloric acid declines with age. Without enough hydrochloric acid to separate B-12 from the large protein molecules that bind it, your vitamin absorption is hampered and B-12 deficiency may result.
Gastrointestinal Disorders
Disorders of the stomach and small intestines can inhibit B-12 absorption. Celiac disease, Crohn's disease, sprue and pancreatic insufficiency are some of the gastrointestinal maladies that affect your ability to derive nutrients from the foods you eat. Alcoholism can also decrease B-12 absorption
History of Gastric Surgery
Some forms of gastrointestinal surgery may decrease your ability to absorb B-12 from the foods you eat. Weight loss or other forms of surgery that involve removing part of the stomach of intestines can decrease your ability to produce enough hydrochloric acid or intrinsic factor.
B-12 Deficiency
B-12 deficiency can take years to develop, because your body stores enough in the liver to last between three and five years. A lack of B-12 due to gastric malabsorption disorders can decrease your ability to produce red blood cells and cause fatigue and weakness. The Linus Pauling Institute states that neurological symptoms are the only sign of B-12 deficiency in up to 25 percent of cases. Nerve damage due to B-12 deficiency can cause tingling in the hands and feet, memory loss and dementia. If not treated in time, nerve damage may be irreversible.
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