What is it?
Vitamin B12, also called cobalamin, is important to good health. It helps maintain healthy nerve cells and red blood cells, and is also needed to make DNA, the genetic material in all cells. Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream.
What foods provide vitamin B12?
Vitamin B12 is naturally found in animal foods including fish, milk and milk products, eggs, meat, and poultry. Fortified breakfast cereals are an excellent source of vitamin B12 and a particularly valuable source for vegetarians. The table of selected food sources of vitamin B12 suggests dietary sources of vitamin B12.
When is a deficiency of vitamin B12 likely to occur?
Diets of most adult Americans provide recommended intakes of vitamin B12, but deficiency may still occur as a result of an inability to absorb B12 from food. It can also occur in individuals with dietary patterns that exclude animal or fortified foods. As a general rule, most individuals who develop a vitamin B12 deficiency have an underlying stomach or intestinal disorder that limits the absorption of vitamin B12. Sometimes the only symptom of these intestinal disorders is anemia resulting from B12 deficiency.
Characteristic signs of B12 deficiency include fatigue, weakness, nausea, constipation, flatulence (gas), loss of appetite, and weight loss. Deficiency also can lead to neurological changes such as numbness and tingling in the hands and feet. Additional symptoms of B12 deficiency are difficulty in maintaining balance, depression, confusion, poor memory, and soreness of the mouth or tongue. Some of these symptoms can also result from a variety of medical conditions other than vitamin B12 deficiency. It is important to have a physician evaluate these symptoms so that appropriate medical care can be given.
Who may need a vitamin B12 supplement to prevent a deficiency?
Individuals with pernicious anemia
Pernicious anemia is a form of anemia that occurs when there is an absence of intrinsic factor, a substance normally present in the stomach. Vitamin B12 binds with intrinsic factor before it is absorbed and used by your body. An absence of intrinsic factor prevents normal absorption of B12 and results in pernicious anemia.
Anyone with pernicious anemia usually needs intramuscular (IM) injections (shots) of vitamin B12. It is very important to remember that pernicious anemia is a chronic condition that should be monitored by a physician. Anyone with pernicious anemia has to take lifelong supplemental vitamin B12.
Vitamin B12 must be separated from protein in food before it can bind with intrinsic factor and be absorbed by your body. Bacterial overgrowth in the stomach and/or atrophic gastritis, an inflammation of the stomach, contribute to vitamin B12 deficiency in adults by limiting secretions of stomach acid needed to separate vitamin B12 from protein in food. Adults 50 years of age and older with these conditions are able to absorb the B12 in fortified foods and dietary supplements. Health care professionals may advise adults over the age of 50 to get their vitamin B12 from a dietary supplement or from foods fortified with vitamin B12 because 10 to 30 percent of older people may be unable to absorb vitamin B12 in food.
Vitamin B-12 (as cyanocobalamin)
- Pharmaceutical Grade: 1000 mcg
Suggested Use: As a dietary supplement, take one tablet daily.
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