[an error occurred while processing this directive]
Also known as cyanocobalamin and B12 cobalamin is the largest molecule of all the vitamins. It is unique in that it is the only vitamin to contain a metal, cobalt. Because of its complexity, cobalamin was not synthesized until 1972.
Like folic acid, cobalamin is an essential participant in nucleic acid synthesis. Cobalamin is also essential to the metabolism of folate, and is essential to the structure and function of the nervous system.
Cobalamin absorption from the gastrointestinal tract is almost nonexistent unless another substance, called the intrinsic factor, is also present. Intrinsic factor is a glycoprotein which is secreted by a normal, healthy stomach. If the intrinsic factor is not present, very large doses of cobalamin (more than .025 mg.) will be only partially absorbed. Other proteins are necessary for transport of the vitamin in the blood and uptake by the cells. These proteins are called transcobalamines.
The cause of cobalamin deficiency (pernicious anemia) is usually the lack of intrinsic factor, not dietary lack of the vitamin. People with pernicious anemia have been found to excrete large amounts of the vitamin when it is given them, indicating that it is not being absorbed.
Animals can synthesize cobalamin (or rather, the bacteria in their gastrointestinal tract can synthesize it), utilizing dietary cobalt. Humans cannot do this, however, and must rely on a dietary source. The only cobalt the human body uses is that which enters via cobalamin.
The symptoms of pernicious anemia include weakness, sore and inflamed tongue, numbness and tingling in the extremities, pallor, weak pulse, stiffness, drowsiness, irritability, depression, and diarrhea.
Pernicious anemia, however, does not always result from a deficiency of cobalamin, not even severe deficiencies. A marginal deficiency could be expected to produce lesser versions of the above symptoms. And any person who suffers such symptoms on a day-to-day basis should first of all suspect some form of nutritional deficit.
However, other symptoms, ranging from mental problems to increased susceptibility to infections, can result. Certain organs or organ systems may be more susceptible to shortfalls in the supply of nutrients, from person to person. Two people with the same diet may suffer totally different symptoms. And a third person might appear perfectly healthy.
Cobalamin appears to play a role in mental health independent of the dementia associated with pernicious anemia. Some people apparently have nervous systems which need more cobalamin to stay healthy. A severe deficiency can land them in the mental hospital, while a marginal deficiency may be just enough to make them very hard to get along with.
A cobalamin deficiency impairs the activity of the immune system, primarily by inhibiting the leukocytes (the white and clear blood cells). Phagocytosis, the devouring of invading organisms by the leukocytes, was reduced to slightly more than one-third of normal. Bacterial killing was decreased, too. Supplementation with the vitamin reversed these effects.
Organ meats are the best sources of cobalamin; muscle meats
and fish supply it in moderate amounts, milk in somewhat
smaller amounts. There are some vegetable sources: sea
vegetables (seaweed such as wakame and kombu) and fermented
soybeans (tempeh). Nutritional yeast can be grown on a
cobalamin-fortified base, and the resultant yeast will provide cobalamin.
Some yeasts are fortified with synthetic cobalamin, too.
Cobalamin is sensitive to light, acids, and alkalies. It is
normally not destroyed in cooking; however, overheating may
Cobalamin is available in supplements ranging from a few micrograms up to a milligram (1000 micrograms).
Vegans (vegetarians who also avoid dairy and eggs) frequently become deficient, though the process may take many years. People with malabsorption conditions may suffer from vitamin B12 deficiency. Individuals suffering from pernicious anemia require high-dose supplements of vitamin B12. Older people with urinary incontinence and hearing loss have been reported to be at increased risk of B12 deficiency.
The RDA for cobalamin ranges from.5 micrograms (.0003 mg.) for infants to four micrograms (.004 mg.) for pregnant women. For adults, the RDA is three micrograms. These ranges are much lower than the doses used therapeutically. If a deficiency is based on dietary lack, improving the diet or supplementation will correct it. However, many deficiencies appear to be from a metabolic defect or a lack of intrinsic factor. In such cases, the intrinsic factor must be taken with any supplement, or the vitamin must be injected in order to bypass faulty absorption. People who have such a metabolic defect usually require one or the other of these treatments for life.
Vitamin B12 supplements are not associated with side effects.
If a person is deficient in vitamin B12 and takes 1,000 mcg of folic acid per day or more, the folic acid can improve anemia caused by the B12 deficiency, but not affect neurological symptoms. This is not a toxicity but rather a partial solution to one of the problems caused by B12 deficiency. The other problems caused by a lack of vitamin B12 (mostly neurological) do not improve with folic acid supplements.
Vitamin B12 deficiencies often occur without anemia (even in people who don't take folic acid supplements). Some doctors do not know that the absence of anemia does not rule out a B12 deficiency. If this confusion delays diagnosis of a vitamin B12 deficiency, the patient could be injured, sometimes permanently. This problem is rare and should not happen with doctors knowledgeable in this area using correct testing procedures.
Anyone supplementing more than 1,000 mcg per day of folic acid needs to be initially evaluated by a doctor of natural medicine to avoid this potential problem.
Water - soluble vitamins are:
Fat-soluble vitamins are: