• Cobalamin, Cyanocobalamin, Hydrocobalamin, Methylcobalamin
• Correcting Deficiency
, an essential nutrient, is also known as cobalamin. The cobal in the name refers to the metal cobalt contained in B
. Vitamin B
is required for the normal activity of nerve cells and works with folate and vitamin B
to lower blood levels of
Anemia is usually (but not always) the first sign of B 12 deficiency. Earlier in this century, doctors coined the name "pernicious anemia" for a stubborn form of anemia that didn't improve even when the patient was given iron supplements. Today we know that pernicious anemia comes about when the stomach fails to excrete a special substance called intrinsic factor. The body needs the intrinsic factor for efficient absorption of vitamin B 12 . In 1948, vitamin B 12 was identified as the cure for pernicious anemia. B 12 deficiency also causes nerve damage, and this may, in some cases, occur without anemia first developing.
Vitamin B 12 has also been proposed as a treatment for numerous other conditions, but as yet there is no definitive evidence that it is effective for any purpose other than correcting deficiency.
Extraordinarily small amounts of vitamin B 12 suffice for daily nutritional needs. The official US and Canadian recommendations for daily intake are as follows:
- 0-6 months: 0.4 mcg
- 7-12 months: 0.5 mcg
- 1-3 years: 0.9 mcg
- 4-8 years: 1.2 mcg
- 9-13 years: 1.8 mcg
- Males and Females
- 14 years and older: 2.4 mcg
- Pregnant Women
- 2.6 mcg
- Nursing Women
- 2.8 mcg
Vitamin B 12 deficiency is rare in the young, but it's not unusual in older people: Probably 10% to 20% of the elderly are deficient in B 12 . 1-4
Similarly, people who take medications that greatly reduce stomach acid, such as
Stomach surgery and other conditions affecting the digestive tract can also lead to B
deficiency. Vitamin B
absorption or levels in the blood may also be impaired by
Vitamin B 12 is found in most animal foods; it is also found only in animal food. Beef, liver, clams, and lamb provide a whopping 80 to 100 mcg of B 12 per 3.5-oz serving, at least 40 times the dietary requirement. Sardines, chicken liver, beef kidney, and calf liver are also good sources, providing between 25 and 60 mcg per serving. Trout, salmon, tuna, eggs, whey, and many cheeses provide at least the recommended daily intake.
: Total vegetarians (vegans) must take vitamin B
supplements or consume B
-fortified foods, or they will eventually become deficient.
Vitamin B 12 is available in three forms: cyanocobalamin, hydrocobalamin, and methylcobalamin. The first is the most widely available and least expensive, but some experts think that the other two forms are preferable.
deficiency can cause anemia and, potentially, nerve damage. The latter may become permanent if the deficiency is not corrected in time. Anemia most often develops first, leading to treatment before permanent nerve damage develops. However, folate supplements can get in the way of this "early warning system." This is why people are cautioned against taking high doses of folate without medical supervision. When taken at a dosage higher than 400 mcg daily, folate can prevent anemia caused by B
deficiency, thereby allowing permanent nerve damage to develop without any warning. More mild deficiencies of vitamin B
may cause elevated levels of homocysteine in the blood, potentially increasing risk of heart disease. (See the
For correcting absorption problems caused by medications, taking vitamin B 12 at the level of dietary requirements should suffice.
For other purposes, enormously higher daily doses—ranging from 100 to 2,000 mcg—are sometimes recommended.
It appears that individuals who take medications that dramatically lower stomach acid, such as
For pernicious anemia, B
injections are traditionally used but research has shown that oral B
works just as well, provided you take enough of it (between 300 and 1,000 mcg daily).
Weak evidence suggests that B
supplements may improve sperm activity and sperm count; on this basis, they could be useful for
One placebo-controlled, double-blind study, enrolling 49 people with eczema, found benefit with a cream containing vitamin B
at a concentration of 0.07%.
On the basis of weak and sometimes contradictory evidence, vitamin B
has been suggested for
Some evidence suggests that people with
Some alternative practitioners recommend the use of injected vitamin B
is also sometimes recommended for numerous other problems, including
One double-blind, placebo-controlled study of 140 people with mildly low B
levels failed to find the supplement
helpful for improving mental function and mood.
Although vitamin B
has been proposed as a treatment for
What Is the Scientific Evidence for Vitamin B 12 ?
Vitamin B 12 deficiencies in men can lead to reduced sperm counts and lowered sperm mobility. For this reason, B 12 supplements have been tried for improving fertility in men with abnormal sperm production. In one double-blind study of 375 infertile men, supplementation with vitamin B 12 produced no benefits on average in the group as a whole. 55 However, in a particular subgroup of men with sufficiently low sperm count and sperm motility, B 12 appeared to be helpful. Such "dredging" of the data is suspect from a scientific point of view, however, and this study cannot be taken as proof of effectiveness.
Vitamin B 12 appears to be extremely safe. However, in some cases very high doses of the vitamin can cause or worsen acne symptoms. 56,57
Interactions You Should Know About
If you are taking:
10. Belaiche J, Zittoun J, Marquet J, et al. Effect of ranitidine on gastric intrinsic factor and cobalamin (vitamin B 12 ) absorption [translated from French]. Gastroenterol Clin Biol. 1983;7:381-384.
14. Baum MK, Javier JJ, Mantero-Atienza E, et al. Zidovudine-associated adverse reactions in a longitudinal study of asymptomatic HIV-1 infected homosexual males. J Acquir Immune Defic Syndr. 1991;4:1218-1226.
15. Deleu D, Louon A, Sivagnanam S, et al. Long-term effects of nitrous oxide anaesthesia on laboratory and clinical parameters in elderly Omani patients: a randomized double-blind study. J Clin Pharm Ther. 2000;25:271-277.
30. Kumamoto Y, Maruta H, Ishigami J, et al. Clinical efficacy of mecobalamin in treatment of oligozoospermia—results of double-blind comparative clinical study [in Japanese; English abstract]. Hinyokika Kiyo. 1988;34:1109-1132.
34. Richman DD, Fischl MA, Grieco MH, et al. The toxicity of azidothymidine (AZT) in the treatment of patients with AIDS and AIDS-related complex. A double-blind, placebo-controlled trial. N Engl J Med. 1987;317:192-197.
38. Kaji R, Kodama M, Imamura A, et al. Effect of ultrahigh-dose methylcobalamin on compound muscle action potentials in amyotrophic lateral sclerosis: a double-blind controlled study. Muscle Nerve. 1998;21:1775-1778.
43. Baig SM, Qureshi GA, Minami M. The interrelation between the deficiency of vitamin B 12 and neurotoxicity of homocysteine with nitrite in some of neurologic disorders. Biogenic Amines. 1998;14:1-14.
50. Kwok T, Tang C, Woo J, et al. Randomized trial of the effect of supplementation on the cognitive function of older people with subnormal cobalamin levels. Int J Geriatr Psychiatry. 1998;13:611-616.
55. Kumamoto Y, Maruta H, Ishigami J, et al. Clinical efficacy of mecobalamin in treatment of oligozoospermia--results of double-blind comparative clinical study [in Japanese; English abstract]. Hinyokika Kiyo. 1988;34:1109-1132.
64. Hvas AM, Juul S, Nexo E, et al. Vitamin B-12 treatment has limited effect on health-related quality of life among individuals with elevated plasma methylmalonic acid: a randomized placebo-controlled study. J Intern Med. 2003;253:146-152.
66. Stucker M, Pieck C, Stoerb C, et al. Topical vitamin B—a new therapeutic approach in atopic dermatitis—evaluation of efficacy and tolerability in a randomized placebo-controlled multicentre clinical trial. Br J Dermatol . 2004;150:977-83.
Last reviewed April 2009 by EBSCO CAM Review Board
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