Vitamin B-12, also called cobalamin, is a water-soluble vitamin found mostly in animal products, primarily red meat. It is likely you are getting enough vitamin B-12 from your diet unless you are a vegan or lack a protein that helps carry vitamin B-12 into your intestinal cells. If you do not get enough vitamin B-12, stored levels eventually diminish and cause a deficiency. The deficiency leads to a form of anemia called megaloblastic anemia.
Vitamin B-12 Status
Vitamin B-12 is the only water-soluble vitamin that can be stored. Nowak and Hanford in "Pathophysiology" state that if intake falls to zero, body stores of vitamin B-12 should meet your body's demand for years. If you have recently shifted your diet to strictly vegan, your body's vitamin B-12 storage may take time to diminish but will eventually need replenishing through supplementation. Very little vitamin B-12 is necessary to maintain a normal status. Only 1 micromilligram of vitamin B-12 daily is required if body stores are adequate.
Intrinsic Factor
If you are experiencing vitamin B-12 deficiency symptoms such as paleness, fatigue, heart palpitations and shortness of breath while consuming adequate dietary sources, consult with your physician about other factors that may be causing these symptoms. A possible scenario is that you do not have the protein in your stomach called the intrinsic factor. The intrinsic factor is responsible for bonding with vitamin B-12 and carrying it through the small intestinal cell walls for absorption into the body. Without the intrinsic factor, vitamin B-12 will escape from the body through urine and not be absorbed. When vitamin B-12 deficiency is caused by a lack of the intrinsic factor, pernicious anemia, a form of megaloblastic anemia, occurs.
Clinical Features of Anemia
Larger-than-normal red blood cells are referred to as megaloblastic anemia that is caused by a vitamin B-12 deficiency or folate deficiency. A blood measurement of the mean corpuscular volume or red blood cell volume and hemoglobin levels will help determine megaloblastic anemia. Low hemoglobin levels and a mean corpuscular volume greater than 100 femtoliters are indicative of megaloblastic anemia. Physical symptoms show with a sore and red tongue, anorexia, numbness and a "prickling" feeling on the skin.
Folate Relationship
It is difficult to determine if vitamin B-12 or folate deficiency is the cause of megaloblastic anemia by physical symptoms. The symptoms of both deficiencies are similar, with the exception of neurological problems, which are more than likely caused by vitamin B-12 deficiency. A blood test is necessary to determine the type of deficiency by measuring two chemical markers, methymalonic acid and homocysteine. Elevated blood levels of homcysteine are indicative of both deficiencies, however, methylmalonic acid is a specific marker for vitamin B-12 deficiency.
References
- "Pathophysiology (3rd Edition)"; T. Nowak and A.G. Handford; 2004
- "Nutritional Assessment (4th Edition)"; R.D. Lee and D. C. Nieman; 2007
- "Textbook of Biochemistry with Clinical Correlations (6th Edition)"; T. Devlin; 2006
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