Also known as cobalamin, vitamin B12 is an essential nutrient with the largest, most complex chemical structure of all other vitamins.
Vitamin B12 comes in several forms: methylcobalamin, 5-deoxyadenosylcobalamin, and cyanocobalamin; however, methylcobalamin and 5-deoxyadenosylcobalamin are the active coenzyme forms used in the body. The third form cyanocobalamin, which is a supplemental form, converts to one of the other forms after ingestion.
Vitamin B12 is absorbed into the blood stream as hydrochloric acid separates from its attached protein.
Vitamin B12 is an essential nutrient that maintains healthy nerve and blood cells and aids in DNA synthesis.
Vitamin B12 is used to combat pernicious anemia, a condition where the body is unable to produce sufficient, healthy red blood cells. Low red blood cell counts mean impaired oxygen transport in the body, resulting in fatigue and weakness.
One 16-week study suggests vitamin B12 may ameliorate sperm quality. Subjects with oligozoospermia, a condition of low sperm concentration, received 6 or 12 mg methylcobalamin doses. Researchers observed an efficacy rate of 37.5% and 39.1% in vitamin B12 supplemented groups, respectively. Researchers determined a long-term treatment with vitamin B12 was useful in ameliorating sperm concentration.
Research reveals supplementing vitamin B12 with folic acid and vitamin B6 may be beneficial in combating age-related macular degeneration.
Also, researchers have shown a link between depression and low red blood cell folate, vitamin B12, and an increase in plasma homocysteine. They suggest a vitamin B12 and folic acid combination “should be tried to improve treatment outcome in depression.”
Vitamin B12 is regarded as safe for most individuals. However, some people may experience itching, blood clots, diarrhea, and serious allergic reactions.
For those with megaloblastic anemia, vitamin B12 may be used, but researchers note serious side effects may occur. Consequently, medical authorities warn against vitamin B12 unless under the supervision of a healthcare professional.
Those with Leber’s disease or an allergy to cobalt or cobalamin should avoid vitamin B12.
According to the Office of Dietary Supplements, National Institutes of Health, average recommended daily amounts for individuals are age-dependent:
- Birth to 6 months .4 mcg
- Infants 7-12 months .5 mcg
- Children 1.3 years: .9 mcg
- Children 4-8 years: 1.2 mcg
- Children 9-13 years: 1.8 mcg
- Teens 14-18 years: 2.4 mcg
- Adults: 2.4 mcg
The studied dose for ameliorating pernicious anemia is 300-10,000 mcg cyanocobalamin per day.
A vitamin B12, folic acid, and pyridoxine combination of 1 mg, 2.5 mg, and 50 mg was studied in treating age-related macular degeneration, respectively.
The dose used in studying depression treatment is 800 mcg folic acid and 1 mg vitamin B12.
-  “Vitamin B12.” Encyclopaedia Britannica.
-  “Vitamin B12.” Linus Pauling Institute Micronutrient Information Center.
-  “Dietary Supplement Fact Sheet: Vitamin B12.” Office of Dietary Supplements, National Institutes of Health.
-  “What Is Pernicious Anemia?” National Heart, Lung, and Blood Institue.
-  Moriyama H, et al. [Studies on the usefulness of long-term, high-dose treatment of methylcobalamin in patients with oligozoospermia.” Hinyokika Kiyo. 1987 Jan;33(1):151-6.
-  Christen WG, Glynn RJ, Chew EY, et al. Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women. Arch Intern Med 2009;169:335-41.
-  Coppen A, Bolander-Gouaille C. “Treatment of depression: time to consider folic acid and B12.” J Psychopharmacol. 2005 Jan;19(1):59-65.
-  “Vitamin B12.” WebMD.