Vitamin B12 sources

Milk, Swiss cheese, Liver, Kidney, beef, Salmon, steak, chicken, Tuna, Yogurt (nonfat plain), Beef, Milk, Swiss cheese, egg.

What Is It?

Vitamin B12 (cobalamin) is a water-soluble member of the B vitamins. All animals and humans need vitamin B12. There is no vitamin B12 in plants since they do not require it or use it. It's paradoxical that the bacteria that live in our guts make more vitamin B12 than we need, but it's not available to us since it cannot be absorbed from the large bowel. There is so much vitamin B12 in feces that the presence of this vitamin in lakes and rivers is used as a measure of fecal contamination. Vegetarian animals like rats, guinea pigs and rabbits eat their own feces-probably as a necessary source of vitamin B12.

What Does It Do?

Without enough vitamin B12, blood formation becomes abnormal. Severe anemia and deficiencies in other blood cells may occur. In addition, in humans, monkeys and other primates, but apparently not in most other animals, vitamin B12 is required to maintain the health of the nerves. Disorders of balance, numbness and tingling in the fingers and toes and even paralysis of the legs may occur during severe and usually prolonged deficiency and may mimic multiple sclerosis. A dementia similar to Alzheimer disease is seen in some people who are very deficient in vitamin B12. The progression of all of these neurological problems is stopped by treatment with vitamin B12, but damage already caused may not be completely reversed.

How Is Deficiency Recognized?

Measuring the amount of vitamin B12 in the blood recognizes deficiency of vitamin B12. These serum B12 assays are readily available and reliable. In a few people, neurological abnormalities may occur with only modestly reduced serum B12 levels, whereas when blood abnormalities occur, the serum B12 level is usually very low. In the former patients, a special test measuring a metabolite called methylmalonic acid will help to identify the deficiency.

How Is Deficiency Treated?

Treatment is easy. Injections of vitamin B12 given every month will maintain body stores, as will tablets of vitamin B12 taken by mouth in large doses (1000 micrograms) every day.

People At Particular Risk For Deficiency Of Vitamin B12

Strict vegetarians (vegans). Depletion usually requires several years; People with pernicious anemia; lack a material called intrinsic factor, a chemical secreted by the stomach's membrane lining that makes absorption of vitamin B-12 from the diet. This is not required to absorb large doses; Scarring, loss or infection of the lower part of the small bowel or diseases such as regional enteritis prevents vitamin B12 absorption. Some surgical procedures performed to cause weight loss can also lead to this deficiency; Elderly people with degenerative diseases of the stomach.

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