|Vitamin B12 (Cobalamin)
|Also Known As:
Vitamin B12, also called cobalamin, is one of eight water-soluble B vitamins.
All B vitamins help the body to convert carbohydrates into glucose (sugar),
which is "burned" to produce energy. These B vitamins, often referred to as B
complex vitamins, are essential in the breakdown of fats and protein. B complex
vitamins also play an important role in maintaining muscle tone lining the
digestive tract and promoting the health of the nervous system, skin, hair,
eyes, mouth, and liver.
Vitamin B12 is an especially important vitamin for maintaining healthy nerve
cells and it aids in the production of DNA and RNA, the body's genetic material.
Vitamin B12 also works closely together with vitamin B9 (folate) to regulate the
formation of red blood cells and to help iron function better in the body. The
synthesis of S-adenosylmethionine (SAMe), a compound involved in immune function
and mood, depends on the participation of folate and vitamin B12.
Similar to other B complex vitamins, cobalamine is considered an
"anti-stress" vitamin because it is believed to enhance the activity of the
immune system and improve the body's ability to withstand stressful
Vitamins B12, B6, and B9 (folate) work closely together to control blood
levels of the amino acid homocysteine. Elevated levels of this substance appear
to be linked with heart disease and, possibly, depression and Alzheimer's
Deficiencies of vitamin B12 are usually caused by a lack of intrinsic factor,
a substance that allows the body to absorb vitamin B12 from the digestive
system. Such a deficiency can cause a range of symptoms including fatigue,
shortness of breath, diarrhea, nervousness, numbness or tingling sensation in
the fingers and toes., People with the blood disorder pernicious anemia do not
produce sufficient intrinsic factor and must take high doses of vitamin B12 to
maintain their health. Similarly, people who have had stomach surgery (for
example, for a severe ulcer) are at risk for vitamin B12 deficiency and
pernicious anemia. They require lifetime B12 injections after the surgery.
Others at risk for B12 deficiency include vegetarians who follow a strict
vegan or macrobiotic diet; those with certain intestinal infections such as
tapeworm and, possibly, Helicobacter pylori (an organism in the intestines that
can cause an ulcer); and those with an eating disorder.
The most important use of vitamin B12 is to
treat the symptoms of pernicious anemia. These symptoms include weakness, pale
skin, diarrhea, weight loss, fever, numbness or tingling sensation in the hands
and feet, loss of balance, confusion, memory loss, and moodiness.
Many studies indicate that patients with
elevated levels of the amino acid homocysteine are roughly 1.7 times more likely
to develop coronary artery disease and 2.5 times more likely to suffer from a
stroke than those with normal levels. Homocysteine levels are strongly
influenced by B complex vitamins, particularly vitamins B9, B6, and B12.
The American Heart Association recommends that, for most people, an adequate
amount of these important B vitamins be obtained from the diet, rather than
taking extra supplements. Under certain circumstances, however, supplements may
be necessary. Such circumstances include elevated homocysteine levels in someone
who already has heart disease or who has a strong family history of heart
disease that developed at a young age.
Vitamin B9 (folate) and vitamin B12 are
critical to the health of the nervous system and to a process that clears
homocysteine from the blood. As stated earlier, homocysteine may contribute to
the development of certain illnesses such as heart disease, depression, and
Alzheimer's disease. Elevated levels of homocysteine and decreased levels of
both folate and vitamin B12 have been found in people with Alzheimer's disease,
but the benefits of supplementation for dementia are not yet known.
Studies suggest that vitamin B9 (folate) may be
associated with depression more than any other nutrient. Between 15% and 38% of
people with depression have low folate levels in their bodies and those with
very low levels tend to be the most depressed. Low folate levels tend to lead to
elevated homocysteine levels. Many healthcare providers recommend a B complex
multivitamin that contains folate as well as vitamins B6 and B12 to improve
symptoms. If the multivitamin with these B vitamins is not enough to bring
elevated homocysteine levels down, the physician may then recommend higher
amounts of folate along with vitamins B6 and B12. Again, these three nutrients
work closely together to bring down high homocysteine levels, which may be
related to the development of depression.
It is especially important for people who have sustained
serious burns to obtain adequate amounts of nutrients in their daily diet. When
skin is burned, a substantial percentage of micronutrients may be lost. This
increases the risk for infection, slows the healing process, prolongs the
hospital stay, and even increases the risk of death. Although it is unclear
which micronutrients are most beneficial for people with burns, many studies
suggest that a multivitamin including the B complex vitamins may aid in the
Keeping bones healthy throughout life depends on
getting sufficient amounts of specific vitamins and minerals, including
phosphorous, magnesium, boron, manganese, copper, zinc, folate, and vitamins C,
K, B6, and B12, and B6.
In addition, some experts believe that high homocysteine levels may
contribute to the development of osteoporosis. If this is the case, then there
may prove to be a role for dietary or supplemental vitamins B9, B6, and B12.
Dietary and supplemental vitamin B complex is
important for normal vision and prevention of cataracts (damage to the lens of
the eye which can lead to cloudy vision). In fact, people with plenty of protein
and vitamins A, B1, B2, and B3 (niacin) in their diet are less likely to develop
cataracts. Plus, taking additional supplements of vitamins C, E, and B complex
(particularly the B1, B2, B9 [folic acid], and B12 [cobalamin] in the complex )
may further protect the lens of your eyes from developing cataracts.
Human Immunodeficiency Virus (HIV)
Blood levels of vitamin B12
are often low in people with HIV. It is unclear, however, what role vitamin B12
supplements would play in treatment. If you have HIV, your levels of vitamin B12
should be followed over time and B12 injections may be considered if levels get
too low, especially if you have symptoms of B12 deficiency.
Population based studies of postmenopausal women
suggest that low vitamin B12 levels in the blood may be associated with an
increased risk for breast cancer. It is not clear whether supplementation with
vitamin B12 reduces the risk of this disease, however.
Studies suggest that vitamin B12 supplements
may improve sperm counts and sperm mobility. Further studies are needed to best
understand how this can help men with a low sperm count or poor sperm
Good dietary sources of vitamin B12 include fish, dairy products, organ meats
(particularly liver and kidney), eggs, beef, and pork.
Vitamin B12 can be found in multivitamins (including children's chewable and
liquid drops), B complex vitamins, and are sold individually. It is available in
both oral (tablets and, capsules) and intranasal formssoftgels, and lozenges.
Vitamin B12 is also sold under the names cobalamin and cyanocobalamin.
|How to Take It|
People whose daily diet includes meat, milk, and other dairy products should
be able to meet the recommended daily requirements without taking a vitamin
supplement. Vegetarians who do not eat any animal protein should take a vitamin
B12 supplement with water, preferably after eating. Elderly people may need
greater amounts of vitamin B12 than younger people because the body's ability to
absorb vitamin B12 from the diet diminishes with age.
People considering B12 supplements should check with a healthcare provider to
find out the most appropriate dosage.
Daily recommendations for dietary vitamin B12 are listed below.
- Newborns to 6 months: 0.4 mcg (adequate intake)
- Infants 6 months to 1 year: 0.5 mcg (adequate intake)
- Children 1 to 3 years: 0.9 mcg (RDA)
- Children 4 to 8 years: 1.2 mcg (RDA)
- Children 9 to 13 years: 1.8 mcg (RDA)
- Adolescents 14 to 18 years: 2.4 mcg (RDA)
- 19 years and older: 2.4 mcg (RDA)*
- Pregnant females: 2.6 mcg (RDA)
- Breastfeeding females: 2.8 mcg (RDA)
*Because 10-30% of older people may not absorb B12 from food very
efficiently, it is
recommended that those older than 50 years meet their daily requirement
mainly through either foods fortified with vitamin B12 or a supplement
Because of the potential for side effects and interactions with medications,
dietary supplements should be taken only under the supervision of a
knowledgeable healthcare provider.
Vitamin B12 is considered safe and non-toxic.
Taking any one of the B complex vitamins by itself for a long period of time
can result in an imbalance of other important B vitamins. For this reason, it is
generally important to take a B complex vitamin with any single B
If you are currently being treated with any of the following medications, you
should not use vitamin B12 supplements without first talking to your healthcare
Vitamin B12 should not be taken at
the same time as the antibiotic tetracycline because it interferes with the
absorption and effectiveness of this medication. Vitamin B12 either alone or in
combination with other B vitamins should be taken at different times of the day
from tetracycline. (All vitamin B complex supplements act in this way and should
therefore be taken at different times from tetracycline.)
In addition, long-term use of antibiotics can deplete vitamin B levels in the
body, particularly B2, B9, B12, and vitamin H (biotin), which is considered part
of the B complex.
The body's ability to absorb vitamin
B12 is decreased when taking stomach acid-reducing medications such as
omeprazole, lansoprazole, ranitidine, cimetidine, or antacids that are often
used to treat gastroesophageal reflux, ulcers or related symptoms. This
interference is most likely to occur as a result of prolonged use (more than one
year) of these medications.
Blood levels of vitamin B12 may be
reduced when taking chemotherapy medications (particularly methotrexate) for
Metformin for diabetes
Blood levels of vitamin B12 may also be
reduced when taking metformin for diabetes.
Phenobarbital and Phenytoin
Long-term treatment with either
phenobarbital and phenytoin for seizure disorders may interfere with the body's
ability to use vitamin B12.
Adachi S, Kawamoto T, Otsuka M, Todoroki T, Fukao K. Enteral vitamin B12
supplements reverse postgastrectomy B12 deficiency. Ann Surg.
Alpert JE, Fava M. Nutrition and depression: the role of folate. Nutrition
Alpert JE, Mischoulon D, Nierenberg AA, Fava M. Nutrition and depression:
focus on folate. Nutrition. 2000;16:544-581.
Antoon AY, Donovan DK. Burn Injuries. In: Behrman RE, Kliegman RM, Jenson HB,
eds. Nelson Textbook of Pediatrics. Philadelphia, Pa: W.B. Saunders
Bauman WA, Shaw S, Jayatilleke E, Spungen AM, Herbert V. Increased intake of
calcium reverses vitamin B12 malabsorption induced by metformin. Diabetes
Booth GL, Wang EE. Preventive health care, 2000 update: screening and
management of hyperhomocysteinemia for the prevention of coronary artery disease
events. The Canadian Task Force on Preventive Health Care. CMAJ.
Bottiglieri T. Folate, vitamin B12, and neuropsychiatric disorders.
Nutrition Rev. 1996;54(12):382-390.
Bottiglieri T, Laundy M, Crellin R, Toone BK, Carney MW, Reynolds EH.
Homocysteine, folate, methylation, and monoamine metabolism in depression. J
Neurol Neurosurg Psychiatry. 2000;69(2):228-232.
Boushey CJ, Beresford SA, Omenn GS, Motulsky AG. A quantitative assessment of
plasma homocysteine as a risk factor for vascular disease. JAMA.
Brattstrom LE, Hultberg BL, Hardebo JE. Folic acid responsive postmenopausal
homocysteinemia. Metabolism. 1985;34(11):1073-1077.
Bunker VW. The role of nutrition in osteoporosis. Br J Biomed Sci.
Carmel R. Cobalamin, the stomach and aging. Am J Clin Nutr.
Choi SW. Vitamin B12 deficiency: a new risk factor for breast cancer?
[Review]. Nutr Rev. 1999;57(8):250-253.
Clarke R, Smith AD, Jobst KA, Refsum H, Sutton L, Veland PM. Folate, vitamin
B12, and serum total homocysteine levels in confirmed Alzheimer disease. Arch
Committee on Dietary Allowances. Recommended Dietary Allowances. National
Academy of Sciences. Accessed at www.nal.usda.gov/fnic/Dietary/rda.html on
January 8, 1999.
Dastur D, Dave U. Effect of prolonged anticonvulsant medication in epileptic
patients: serum lipids, vitamins B6, B12 and folic acid, proteins and fine
structure of liver. Epilepsia. 1987;28:147-159.
De-Souza DA, Greene LJ. Pharmacological nutrition after burn injury. J
Eikelboom JW, Lonn E, Genest J, Hankey G, Yusuf S. Homocyst(e)ine and
cardiovascular disease: a critical review of the epidemiologic evidence. Ann
Intern Med. 1999;131:363-375.
Ekhard ZE, Filer LJ, eds. Present Knowledge in Nutrition. 7th ed.
Washington, DC: ILSI Press; 1996:191-201.
Fugh-Berman A, Cott JM. Dietary supplements and natural products as
psychotherapeutic agents. Psychosom Med. 1999;61:712-728.
Howden CW. Vitamin B12 levels during prolonged treatment with proton pump
inhibitors. J Clin Gastroenterol. 1999;30(1):29-33.
Hurter T, Reis HE, Borchard F. Disorders of intestinal absorption in patients
treated with cytostatic chemotherapy [in German]. Z Gastroenterol.
Ingram CF, Fleming AF, Patel M, Galpin JS. The value of intrinsic factor
antibody test in diagnosing pernicious anaemia. Cent Afr J Med.
Kaptan K, Beyan C, Ural AU, et al. Helicobacter pylori
- is it a novel causative agent in vitamin B12
deficiency? Arch Intern Med. 2000;160(9):1349-1353.
Kass-Annese B. Alternative therapies for menopause. Clin Obstet
Kelly GS. Nutritional and botanical interventions to assist with the
adaptation to stress. Alt Med Rev. 1999;4(4):249-265.
Kirschmann GJ, Kirschmann JD. Nutrition Almanac. 4th ed. New York:
Kris-Etherton P, Eckel RH, Howard BV, St. Jeor S, Bazzarre TL. Lyon diet
heart study. Benefits of a Mediterranean-style, National Cholesterol Education
Program/American Heart Association Step I dietary pattern on cardiovascular
disease. Circulation. 2001;103:1823-1825.
Kuzminski AM, Del Giacco EJ, Allen RH, Stabler SP, Lindenbaum J. Effective
treatment of cobalamin deficiency with oral cobalamin. Blood.
Lederle FA. Oral cobalamin for pernicious anemia. Medicine's best kept
secret? JAMA. 1991;265:94-95.
Lee AJ. Metformin in noninsulin-dependent diabetes mellitis.
Louwman MW, van Dusseldorp M, van de Vijver FJ, et al. Signs of impaired
cognitive function in adolescents with marginal cobalamin status. Am J Clin
Malinow MR, Bostom AG, Krauss RM. Homocyst(e)ine, diet, and cardiovascular
disease. A statement for healthcare professionals from the nutrition committee,
American Heart Association. Circulation. 1999;99:178-182.
McKevoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of
Health-System Pharmacists, 1998.
Meyer NA, Muller MJ, Herndon DN. Nutrient support of the healing wound.
New Horizons. 1994;2(2):202-214.
Nilsson-Ehle H. Age-related changes in cobalamin (vitamin B12) handling.
Implications for therapy. Drugs Aging.
Nutrients and Nutritional Agents. In: Kastrup EK, Hines Burnham T, Short RM,
et al, eds. Drug Facts and Comparisons. St. Louis, Mo: Facts and
Omray A. Evaluation of pharmacokinetic parameters of tetracylcine
hydrochloride upon oral administration with vitamin C and vitamin B complex.
Hindustan Antibiot Bull. 1981;23(VI):33-37.
Remacha AF, Cadafalch J. Cobalamin deficiency in patients infected with the
human immunodeficiency virus. Semin Hematol.
Schnyder G. Decreased rate of coronary restinosis after lowering of plasma
homocysteine levels. N Engl J Med. 2001;345(22):1593-1600.
Schumann K. Interactions between drugs and vitamins in advanced age. Int J
Vit Nutr Res. 1999;69(3):173-178.
Sinclair S. Male infertility: nutritional and environmental considerations.
Alt Med Rev. 2000;5(1):28-38.
Snowdon DA, Tully CL, Smith CD, Riley KR, Markesbery WR. Serum folate and the
severity of atrophy of the neocortex in Alzheimer disease: findings from the Nun
Study. Am J Clin Nutr. 2000;71:993-998.
Termanin B, Gibril F, Sutliff VE, Yu F, Venzon DJ, Jensen RT. Effect of
long-term gastric acid suppressive therapy on serum vitamin B12 levels in
patients with Zollinger-Ellison syndrome. Am J Med. 1998;104(5):422-430.
Verhaeverbeke I, Mets T, Mulkens K, Vandewoude M. Normalization of low
vitamin B12 serum levels in older people by oral treatment. J Am Geriatr
Wang HX. Vitamin B12 and folate in relation to the development of Alzheimer's
disease. Neurology. 2001;56:1188-1194.
Weir DG, Scott JM. Vitamin B12 "cobalamin." In: Shils, ME, Olson JA, Shike M,
Ross AC, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore,
MD: Williams & Wilkins; 1999:447-458.
Wu K, Helzlsouer KJ, Comstock GW, Hoffman SC, Nadeau MR, Selhub J. A
prospective study on folate, B12, and pyridoxal 5'-phosphate (B6) and breast
Cancer Epidemiol Biomarkers Prev. 1999;8(3):209-217.
Young SN. The use of diet and dietary components in the study of factors
controlling affect in humans: a review. J Psychiatr Neurosci.
|Review Date: April 2002|
|Reviewed By: Participants in the review process include: Ruth DeBusk, RD, PhD, Editor,
Nutrition in Complementary Care, Tallahassee, FL; Jacqueline A. Hart, MD,
Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University
and Senior Medical Editor Integrative Medicine, Boston, MA; Gary Kracoff, RPh
(Pediatric Dosing section February 2001), Johnson Drugs, Natick, Ma; Steven
Ottariono, RPh (Pediatric Dosing section February 2001), Veteran's
Administrative Hospital, Londonderry, NH. All interaction sections have also
been reviewed by a team of experts including Joseph Lamb, MD (July 2000), The
Integrative Medicine Works, Alexandria, VA;Enrico Liva, ND, RPh (August 2000),
Vital Nutrients, Middletown, CT; Brian T Sanderoff, PD, BS in Pharmacy (March
2000), Clinical Assistant Professor, University of Maryland School of Pharmacy;
President, Your Prescription for Health, Owings Mills, MD; Ira Zunin, MD, MPH,
MBA (July 2000), President and Chairman, Hawaii State Consortium for Integrative
Medicine, Honolulu, HI.|
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