Vitamin B12 Deficiency
Vitamin B12 (cobalamin) deficiency is a factor in many disorders. The absorption of dietary vitamin B12 occurs in the small intestine and requires a secretion from the stomach known as intrinsic factor. If intrinsic factor is deficient, absorption of vitamin B12 is severely diminished. Vitamin B12 deficiency impairs the body’s ability to make blood, accelerates blood cell destruction, and damages the nervous system. The result is pernicious anemia (PA). In the classical definition, PA refers only to B12 deficiency anemia caused by a lack of intrinsic factor.
True PA is probably an autoimmune disease. The immune system destroys cells in the stomach that secrete intrinsic factor. Many people with PA have both chronic inflammation of the stomach lining, called atrophic gastritis, and antibodies that fight their intrinsic factor-secreting cells.
The term pernicious anemia is sometimes used colloquially to refer to any anemia caused by vitamin B12 deficiency. Vitamin B12 deficiency can be due to malabsorption of dietary B12 despite normal levels of intrinsic factor. For example, celiac disease and Crohn’s disease may cause B12 malabsorption, which can lead to anemia. Less common causes of B12 deficiency include gastrointestinal surgery, pancreatic disease, intestinal parasites, and certain drugs. Pregnancy, hyperthyroidism, and advanced stages of cancer may increase the body’s requirement for B12, sometimes leading to a deficiency state.
Low stomach acid, known as hypochlorhydria, interferes with the absorption of B12 from food but not from supplements. Aging is associated with a decrease in the normal secretion of stomach acid. As a result, some older people with normal levels of intrinsic factor and with no clear cause for malabsorption will become vitamin B12-deficient unless they take at least a few micrograms per day of vitamin B12 from supplements.
What are the symptoms of vitamin B12 deficiency?
Symptoms of severe vitamin B12 deficiency may include burning of the tongue, fatigue, weakness, loss of appetite, intermittent constipation and diarrhea, abdominal pain, weight loss, menstrual symptoms, psychological symptoms, and nervous system problems, such as numbness and tingling in the feet and hands. Most symptoms can occur before the deficiency is severe enough to cause anemia. Healthcare professionals have a series of laboratory tests that can determine B12 deficiency at earlier stages that are not accompanied by anemia.
How is it treated?
Conventional treatment includes lifelong intramuscular vitamin B12 injections. In some cases, cortisone-like drugs (e.g., prednisone [Deltasone®, Orasone®, and Meticorten®]) may also be recommended.
Dietary changes that may be helpful:
Vitamin B12 is found in significant amounts only in animal protein foods— meat and poultry, fish, eggs, and dairy products. Even small amounts of these foods supply sufficient amounts of vitamin B12 to provide enough for healthy people.
Lifestyle changes that may be helpful:
Alcohol abuse can lead to gastritis and damage to the lining of the intestines, both of which can interfere with vitamin B12 absorption. If B12 deficiency is due to alcoholism, abstinence may prevent further impairment of B12 absorption.
Nutritional supplements that may be helpful:
Normally, only 3 to 4 mcg per day of vitamin B12 is required to prevent dietary deficiency. If gastrointestinal function is normal, even these small amounts of vitamin B12 from oral supplementation can prevent deficiency in vegans. If a deficiency already exists, most doctors will recommend an initial vitamin B12 injection, then oral amounts ranging from 500 mcg to 1,000 mcg per day until symptoms subside; this is followed by a maintenance level of approximately 10 mcg per day to prevent future deficiencies. |
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