Vitamin B-12, or cobalamin, is key in the functioning of several enzymes. Enzymes are special proteins that increase the rates of chemical reactions, helping the body perform many activities. Very low B-12 has a number of causes and can result in cellular dysfunction and damage to the body. A doctor should diagnose and treat vitamin deficiencies.
Causes
Inadequate dietary intake can cause a vitamin B-12 deficiency. Vegetarians are at higher risk than non-vegetarians as v-tamin B-12 is naturally found in animal products -- although some foods are fortified with vitamin B-12. Alcoholics and the elderly are also at risk for deficiency. In addition, gastrointestinal diseases such as atrophic gastritis, in which the immune system causes inflammation of the stomach, can lead to decreased vitamin B-12 from failed absorption.
Symptoms and Signs
The symptoms of vitamin B-12 deficiency may be silent and the disease can progress for some time unnoticed; it can cause a disease called pernicious anemia. In this condition, there is a low level of red blood cells, responsible for oxygen transport. This can cause fatigue. In addition, vitamin B-12 deficiency can damage the nerves, leading to pain, tingling, and difficulty sensing the limbs position in the environment.
Diagnosis
The diagnosis of vitamin B-12 deficiency is made by a history, physical exam and laboratory findings. Vitamin B-12 levels are usually low, and levels of two other chemicals, homocysteine and methylmalonic acid, are high. A blood smear may show low numbers of red blood cells that are enlarged in size, and there can be a history of nerve symptoms.
Function of B-12 and Mechanism of Disease
Vitamin B-12 helps synthesize DNA. Red blood cells are made in the bone marrow from instructions in the DNA in bone marrow stem cells. Without adequate vitamin B-12, the cells are made in lower numbers and the cell membranes continue to grow larger than is normal. The deficiency damages the myelin sheath -- the protective covering around the nerves -- and eventually leads to nerve damage, which can cause pain, tingling and a loss of sensation.
Treatment
The treatment of vitamin B-12 deficiency is generally administration of vitamin B-12. Oral dosing of vitamin B-12 is generally not affective if the cause is a gastrointestinal disorder because the GI tract will not be able to absorb it. In this case, the vitamin is injected.
References
- "Current Medical Diagnosis and Treatment 2011"; Stephen McPhee, Maxine Papadakis, and
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci et al.; 17th Ed 2008
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar et al.; 8th Ed 2009
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