Vitamin B12 (a.k.a. Cobalamine, subtypes Methylcobalamine, Cyanocobalamine and Hydroxycobalamine)
B12 is necessary in small amounts for the formation of proteins, red blood cells, the function of the central nervous system (production of myelin — the stuff which serves as insulation for the "wires" of the brain, spinal cord and peripheral nerves) and maintenance of the inner lining of the intestinal tract.
B12 is not available from vegetable sources and is produced only by microbes (bacteria and algae). Microbes found in the mouth and intestine produce sufficient B12 for most people. The body generally has stored a three to eight year supply of B12.
Since the introduction of techniques to kill micro-organisms associated with food, it has become possible, although extremely unlikely, that a strict vegetarian can develop B12 deficiency. To guard against this, within three years of commencing a strict vegetarian diet, you should add tempe, miso, soy sauce, or tamari sauce to your diet on an occasional basis. These foods all contain B12.
It is true that B12 is present in animal products, but when you look at what else also is present, you will want to choose to learn a little about these not-so-well-known oriental foods which contain B12. An abundance of B12 helps in the production of red blood cells, helps keep the nervous system running smoothly and helps maintain the integrity of the intestinal mucosa.
A B12 blood test tells the doctor the level of B12 is in the blood. However, B12 has its action inside cells. Some people are deficient B12 at the intracellular level while the serum tests in the normal range. Some people cannot transfer B12 that is absorbed from serum to the tissues. Methylmalonic acid and homocysteine tests should be done to see if either or both of those has risen. These are metabolites of B12. If, when B12 is given, these high metabolite(s) fall, it is likely that the patient needed the B12 which was administered.
A small percentage of patients who have B12 deficiency do not show this with testing. I believe everyone with neurologic symptoms should be administered B12. Many people do not have a response to the first injection, or even the first several injections. Some will respond with increased discomfort as the sensory nerves begin to repair. Some people don’t have an obvious response for many months, but that is unusual.
A person should take at least 1000 mcg orally per day in case absorbtion is severely impaired. Most people with severe malabsorption can absorb enough for daily use and to begin replenishing stored B12 if they take that much. At least 1000 mcg. More is fine.
The methylcobalamin form of B12 is now available. Taking methylcobalamin eliminates the need for the body to convert cyanocobalamin or hydroxycobalamin into methylcobalamin which is the form that is needed by the body for life and to repair nerves.