If your body lacks adequate amounts of vitamin B12, you're at risk of developing a condition known as pernicious anemia. The importance of diet in relation to this condition was discovered in 1926, when it was found that eating liver cured the illness. But the "anti-pernicious anemia factor" in liver was not identified as vitamin B12 until much later. Since then, scientists have discovered a range of foods rich in vitamin B12, and B12 supplements have become available.
Function
Vitamin B12 helps cell division and the production and repair of the fatty layer that insulates your nerves. One of the first signs of B12 deficiency is anemia. When anemia develops, blood cannot carry enough oxygen. And if the insulating layer covering your nerves is not maintained, it degenerates, and irreversible neurological damage occurs.
Sources
Adults require only a tiny amount of vitamin B12 -- 2.4 mcg -- each day, according to the University of Maryland Medical Center. Since B12 is common in animal-based foods such as meat, fish and dairy products, you're unlikely to be deficient in this vitamin. Vegetarians can get enough B12 in eggs and milk to stay healthy. Because B12 can be stored in your body and even recycled, your diet would need to lack it for quite a few years before levels dropped enough to cause health problems. Only vegans are likely to lack B12.
Vegans
There are no reliable vegetable sources of vitamin B12, notes the University of California-San Diego. But vegan diets can be high in folic acid, which helps prevent anemia. Vegans are advised to take yeast extract, eat fortified breakfast cereals and use vitamin supplements to avoid anemia.
Considerations
Nutrients such as vitamin B12 are absorbed from your digestive system into your blood. Once in your blood, they become available for your body to use. But B12 cannot be absorbed on its own. It must combine with a protein produced in the stomach called "intrinsic factor." Without this factor, anemia will develop even if you get enough B12 in your diet. If you suffer from celiac disease or Crohn's disease or if you have had surgery on your stomach or intestines, your body may not be able to absorb B12 even when intrinsic factor is produced.
Symptoms of Deficiency
Anemia is the primary result of vitamin B12 deficiency. Symptoms include breathlessness, pallor, lack of energy and poor resistance to infection. When the anemia becomes life-threatening, it is called pernicious anemia. Other signs include tongue soreness and menstrual disorders. The fatty insulating layer surrounding nerve cells becomes affected, and nerve damage occurs. This causes tingling sensations in your fingers and toes, staggering, confusion and dementia. Death will result if the deficiency is not corrected.
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