Vitamin B12 (cyanocobalamin) is an oxygen carrier; it decreases blood cholesterol; it metabolizes fat. Vitamin B12 is essential in humans for healthy nerve tissues. Its deficiency is associated with heart palpitations. The term "Vitamin B12" refers to a group of cobalamin compounds, of which the most frequently used is cyanocobalamin. All vitamin B12 found in nature is made by microorganisms (bacteria essentially), and none is found in sterile plants. In the early to mid 1800s, an unrecognized vitamin B12 deficiency was referred to as pernicious anemia because it was almost always fatal. It was not until 1948, though, that researchers finally isolated the active principle in liver now called vitamin B12. The isolation used a charcoal filter that added the stabilizing effects of cyanide, thus cyanocobalamin is one of the major stable forms used today for supplementation purposes.
The best sources of B12 are animal-derived: liver, meat, salt-water fish, oysters, milk, eggs, aged cheese such as Roquefort, and fortified brewer's yeast. Vitamin B12 occurs naturally in the soil and on the surface of unwashed fruits and vegetables. Those on an animal-free diet may wish to eat unwashed, organic produce whenever possible.
There is debate over the reliability of non-animal sources of Vitamin B12. It was found that people on vegan diets had lower levels of serum B12 levels than the general population. In particular, infants breast-fed or fed a macrobiotic diet directly are at a great risk of developing B12 deficiency.
Non-animal sources which claim to have significant amounts of B12 such as tempeh, micro-algaes (spirulina, chlorella), miso, tamari, and sea vegetables (nori, arame, kombu, wakame) have been found to have negligible amounts, or B12 analogues that show up on lab tests, but don't have the activity of real B12.
It should be noted that there are different techniques for measuring the B12 content of foods. Furthermore, the B12 content in fermented foods, such as tempeh, may be different due to varying production techniques. In Indonesia, traditionally-produced tempeh is loaded with B12-producing bacteria which grow on the molds commonly growing on the food. In the U.S., however, large scale production and improved sanitation decreases the mold and bacteria and the subsequent B12 content of the food. The most reliable non-animal, but natural, source of B12 seems to be fortified brewers yeast.
Blood levels of B12 indicate that sublingual B12 becomes available as early as 15 minutes after administration and are still elevated at 24 hours, suggesting that a once-daily dose of 2,000-4,000mcg would be an effective preventive measure. [Bhat N.K. – Presentation at the 43rd Annual Meeting, American Academy of Allergy and Immunology, 1987]
A year's supply of 1,000mcg vitamin B12 tablets costs under $20, which is less than the cost of going to the doctor's office for injections. On the other hand, patients who are likely to be noncompliant with oral therapy should be seen regularly by a doctor and treated with intramuscular injections.
The current US RDA for vitamin B12 is 6mcg, but less for children and more for nursing and pregnant women. For those suspected of having low B12 levels, 2,000mcg once a day for two weeks sublingually should replenish stores. Those with problems absorbing B12 should continue taking their B12 sublinbgually.
When vitamin B12 is being used for its pharmacological effects, as in the treatment of fatigue, Bell's palsy, diabetic neuropathy, subdeltoid bursitis, or asthma, intramuscular injections appear to be preferable to oral administration. Although there is little published research in this area, clinical observations suggest that orally administered vitamin B12 is not particularly effective against these conditions. It appears that very high serum concentrations are usually needed for vitamin B12 to exert its pharmacological effects, and that these serum concentrations can be achieved only with IM administration.
There are two basic ways to use supplements – weekly or daily. Probably the simplest method is to chew up one B12 supplement containing 2,000mcg or more once a week. The reason you should ideally chew or let it dissolve under your tongue is to enhance absorption. For some people it is hard to remember to take something once a week and they may prefer to get into the habit of taking something every day, which is more physiologically natural.
If you take your B12 supplement every day then you can take much less – you only need about a 100mcg a day that way. This can be achieved through chewing up the smallest tablet you can find every day, or even just a piece of one tablet.
Because many people with vitiligo also have stomach malfunction, they do not absorb vitamin B12 and folic acid very well. This may be part of the reason why these nutrients, along with vitamin C, are often successfully used as part of a vitiligo repigmentation program. Suggested doses are 5mg folic acid and 1000mg vitamin C, twice daily. For the best chance of success, the vitamin B12 should be given by injection, 1000mcg weekly. Several months are usually required before early repigmentation is seen.
Low B12 levels have been found to be related to self-reported overall distress level and specifically to depression, anxiety, confusion, and possibly nervousness as well as to clinically rated depressed and anxious mood. [J Psychosom Res 2000 Feb 1; 48(2): pp.177-85]
Supplementation with B12 may reduce sulfite sensitivity. In one study the oxidative action of vitamin B12 was able to block a sulfite-induced bronchospasm in 4 out of 5 asthmatic children. In another study, the following conditions responded to B12 use: Intractable asthma – 18 out of 20 patients improved; Chronic urticaria – 9/10 improved; Chronic contact dermatitis – 6/6 improved; Atopic dermatitis – 1/10 greatly improved and 5/10 moderately improved with 1000mcg IM once weekly for 4 weeks. [J Allergy 2: 183- 5, 1951]
Blood levels of B12 indicate that sublingual B12 becomes available as early as 15 minutes after administration and is still elevated at 24 hours, suggesting that a once-daily dose of 2000-4000mcg would be an effective prophylactic measure. [Bhat N.K. – Presentation at the 43rd Annual Meeting, American Academy of Allergy and Immunology, 1987]
Methylcobalamin, a form of vitamin B12, was compared with steroids in a trial involving 60 patients with Bell's palsy. The shortest time required for complete recovery of facial nerve function occurred in the group receiving Methylcobalamin alone. A therapeutic dose would be a minimum of 1500mcg and a maximum of 6000mcg per day, by injection. It was administered by intramuscular injection 3 times weekly for 8 weeks (or until recovery). The results of this study have not been validated, and administration of methylcobalamin has not become a common treatment.
Cyanocobalamin is reported to have worked in a couple chronic cases at high doses also. [J Indian Med Assoc 33: pp.129- 31, 1959]
Chronic mild to moderate B12 deficiency may be associated with nervousness. A study was carried out on 1081 healthy young men aged 17-29 which measured current mental state through the 'Adjective Check List' test. There was a very high correlation (p<0.05) between those found to be chronically deficient in vitamin B12 (based on repeated measures of plasma cobalamin levels) and those who were found to be significantly more anxious.
Treatment is highly effective. The form of vitamin B12 known as hydroxocobalamin is given by injection into a muscle twice during the first week and then weekly until the anemia and all other symptoms of deficiency have been fully corrected. It may be necessary to stay on a maintenance dosage of vitamin B12 every three months for life to stop the problem coming back.
Vitamin B12 (with or without folic acid) has been reported in studies from the 1950s to help some people with hepatitis.  Vitamin B12 injections are likely to be more beneficial than oral administration, though 1,000mcg taken orally each day can also be supplemented.
 Campbell RE, Pruitt FW. Vitamin B12 in the treatment of viral hepatitis. Am J Med Sci 1952;224: pp.252-62
 Campbell RE, Pruitt FW. The effect of vitamin B12 and folic acid in the treatment of viral hepatitis. Am J Med Sci 1955;229: pp.8-15
In one clinical trial, weekly 1,000mcg intramuscular injections produced definite improvement in asthmatic children. Of 20 patients, 18 showed less shortness of breath on exertion, as well as improved appetite, sleep, and general condition. When given sublingually prior to a sulfite challenge, vitamin B12 appears to be especially effective in cases of asthma caused by sulfite sensitivity.