Vitamin B12 plays important roles in DNA synthesis, nerve health and the formation of red blood cells. A vitamin B12 deficiency disorder, more commonly referred to as pernicious anemia or megaloblastic anemia, occurs when there is not enough vitamin B12 in the body to make an adequate amount of red blood cells.
Vitamin B12 Absorption
The cells in the stomach, called the parietal cells, produce and release a protein called intrinsic factor. When vitamin B12 enters the stomach, it binds to intrinsic factor and is carried through the stomach into the small intestine. Intrinsic factor then ensures that vitamin B12 is properly absorbed through the small intestine where it can be deposited into the bloodstream. The body cannot successfully absorb vitamin B12 without intrinsic factor.
Causes
One of the most common causes for pernicious anemia is a lack of intrinsic factor. The destruction of parietal cells from autoimmune disorders or prior stomach surgery that removed all or a portion of the stomach may cause a lack of intrinsic factor.
Another cause of pernicious anemia is a lack of absorption in the small intestine. According to MayoClinic.com, improper absorption may be caused by infections, prior intestinal surgery, overgrowth of digestive bacteria, digestive diseases or certain medications.
Rarely, a lack of vitamin B12 in the diet can lead to pernicious anemia. According to the National Heart, Lung and Blood Institute, this is most common in strict vegetarians because vitamin B12 is most abundant in animal sources.
Symptoms
Initially, a vitamin B12 deficiency may not cause any symptoms. As the deficiency worsens, it can cause fatigue, shortness of breath, dizziness, headaches, chest pain and paleness in the nail beds and gums. The digestive tract is also affected. This causes nausea, heartburn, bloating, gas, loss of appetite and weight loss. If a vitamin B12 deficiency is left untreated for too long, it can cause damage to the nerves. Nerve damage causes abnormal sensations, such as tingling and numbness in the extremities, muscle weakness and loss of normal reflexes.
Treatment
Treatment for a vitamin B12 deficiency depends on the cause. If the vitamin B12 deficiency is a result of some type of malabsorption, the vitamin must be regularly injected directly into the bloodstream. Those with pernicious anemia as a result of improper diet usually benefit from oral supplementation and an increase in dietary B12.
Food Sources
The best sources of vitamin B12 include organ meats, such as liver, fish, beef, eggs and poultry. Other sources included fortified cereals and breads.
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