Vitamin B12, or cobalamin, is often called the "energy vitamin," because injections of this nutrient have routinely been administered to elderly people to improve their vitality. Vitamin B12 is involved in the synthesis of DNA and RNA, the production of normal red blood cells and the metabolism of carbohydrates, proteins and fats. Vitamin B12 is essential for maintaining the myelin sheath, or white matter, that nourishes and protects your nerve cells.
Causes of Deficiency
Deficiency of vitamin B12 usually stems from inadequate absorption. Poor absorption, in turn, results either from a deficiency of intrinsic factor, a special protein that binds to vitamin B12 and facilitates its assimilation, or from intestinal abnormalities, such as celiac disease or bowel surgery. According to Dr. Elson Haas, author of "Staying Healthy with Nutrition," strict vegans who do not take supplemental B12 can develop deficiency, because this nutrient is not found in plants. Pernicious anemia, a term often mistakenly applied to all forms of vitamin B12 deficiency, specifically refers to the deficiency caused by damage to acid-secreting cells in the stomach and the subsequent loss of intrinsic factor.
Fatigue
Vitamin B12 participates in the production of hemoglobin, the protein within red blood cells that carries oxygen through your bloodstream. Vitamin B12 deficiency results in the production of abnormally large, poorly functioning red corpuscles. Without robust red blood cells, oxygen delivery to your tissues falls, resulting in fatigue, poor exercise tolerance and decreased stamina.
Gastrointestinal
Vitamin B12 deficiency is frequently associated with vague, nonspecific gastrointestinal complaints, such as loss of appetite, constipation and abdominal pain. Glossitis, a classic sign of vitamin B12 deficiency that is characterized by a smooth and reddened tongue, is not as frequent a finding as was once believed.
Neurologic
The neurologic signs and symptoms of vitamin B12 deficiency can develop independently of anemia or other manifestations. In the early stages of deficiency, you may feel weak, and the ability to detect vibration or determine position in your extremities will diminish. Without supplemental B12, your symptoms worsen, and muscle spasticity, poor coordination, loss of balance and abnormal tendon reflexes develop. Mental disturbances are not uncommon and include irritability, depression, confusion and paranoia. If vitamin B12 deficiency is left untreated, neurologic damage is progressive and irreversible.
Considerations
Because your body can store vitamin B12, the symptoms of deficiency usually develop insidiously over months or even years. Your body can partially adapt to some manifestations of deficiency, such as anemia, so once neurologic symptoms occur, the deficiency has probably been present for many weeks. Treatment is straightforward and requires supplementation with large doses of vitamin B12. As the deficiency improves, dosages can be reduced. Oral supplementation is sufficient for treating most cases of vitamin B12 deficiency, but severe deficits may require injections. If you think you may be suffering from vitamin B12 deficiency, your doctor can perform simple blood tests to confirm the diagnosis.
References
- "Staying Healthy with Nutrition: Vitamin B12"; Elson M. Haas, M.D.; 2006
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Vitamin B12"; Mark H. Beers, M.D., Editor-In-Chief; 2006
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