Vitamin B12 helps your body create healthy red blood cells and plays a role in maintaining the health of your nerves. Your body also needs vitamin B12 in order to synthesize certain amino acids and fatty acids. Lab Tests Online notes that your body can store 3 to 5 years worth of vitamin B12. Because of this, deficiencies of the vitamin are rare. When a vitamin B12 deficiency does develop, it is usually the result of an underlying condition.
Physiology
The parietal cells in your stomach produce a protein called intrinsic factor. When you eat foods that contain vitamin B12, intrinsic factor binds to the vitamin in the small intestine so that your body can properly absorb it. Without intrinsic factor, you would not be able to absorb vitamin B12 regardless of how much of the vitamin you consume.
Pernicious Anemia
One of the most common causes of a vitamin B12 deficiency is lack of intrinsic factor. Some people are not able to produce the protein and therefore cannot absorb vitamin B12. This leads to a lack of healthy red blood cells, a condition medically referred to as pernicious anemia. A lack of intrinsic factor can occur after an abnormal autoimmune response damages the parietal cells. The parietal cells can also be destroyed following surgery to remove all or part of the stomach, according to the National Heart, Lung and Blood Institute.
Other Causes
A vitamin B12 deficiency can also develop as a result of malabsorption in the small intestine. Malabsorption in the small intestine can be caused by a variety of different conditions including celiac disease, Crohn's disease, certain medications, surgical removal of all or part of the intestine, excess bacterial growth or a tapeworm infection.
In rare cases, vitamin B12 deficiency can develop due to a lack of vitamin B12 in the diet. The National Heart, Lung and Blood Institute notes that strict vegetarians are most likely to develop B12 deficiency due to poor diet because the richest sources of vitamin B12 are animal-based foods, such as meat, poultry and eggs.
Symptoms
The most common symptom of a vitamin B12 deficiency is fatigue. Someone who is deficient may also experience lightheadedness, loss of appetite, pale skin, shortness of breath, difficulty concentrating, diarrhea or constipation. If left untreated, a vitamin B12 deficiency can result in nerve damage, which manifests as confusion, loss of balance, muscle weakness and numbness in the hands and feet.
Treatment
If vitamin B12 deficiency is caused by a lack of intrinsic factor, lifelong vitamin B12 injections are usually required. A vitamin B12 deficiency from other causes can usually be corrected with oral supplementation of the vitamin. If an underlying medical condition is causing the deficiency, it is important to treat that condition as well.
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