Definition of Vitamin B12
Vitamin B12: A vitamin important for the normal formation
of red blood cells and the health of the nerve tissues.
Undetected and untreated vitamin B12 deficiency can lead to
anemia and permanent nerve and brain damage.
Pernicious anemia is a blood
disorder caused by inadequate vitamin B12 in the blood.
Patients who have this disorder do not produce the protein substance in the stomach that allows the body to absorb vitamin B12. This
substance is called intrinsic factor (IF).
Pernicious anemia is simply treated with injections of vitamin B12. The vitamin B12 has to be administered by injection because people with PA do not have IF (or an effective
form of IF) and so cannot absorb vitamin B12 taken by
mouth.
Pernicious anemia has also been called Addison's anemia, addisonian anemia, Biermer's anemia.
Patients with Crohn's disease involving the small intestine
(Crohn's ileitis) or who have undergone small intestine
resection may not be able to absorb vitamin B12.
Strict vegetarians who consume no animal products can
develop B12 deficiency since there is a lack of B12 in
vegetables.
The recommended daily allowances of vitamin B12 in the
United States are 2mcg for infants, 3 mcg for children
under 4 years old, 6mcg for children over 4 years old and
adults, and 8 mcg for pregnant women.
It is recommended for adults to take one multivitamin
daily. One multivitamin a day is safe and inexpensive. The
multivitamin should contain 400 micrograms of folic acid,
approximately 2-3 mg of vitamin B6, 6-9 micrograms of
vitamin of B12, and 400 IU of vitamin D. The folic acid and
the other B vitamins can help lower homocysteine. The
vitamin D is one of the important factors in preventing
osteoporosis.
High blood homocysteine levels have been found to be a risk
factor for atherosclerosis and heart disease. Most doctors
will treat homocysteine levels higher than 9-10umol/liter.
A doctor experienced in treating coronary heart disease
should supervise the treatment of hyperhomocysteinemia.
Treatment involves high doses of the B vitamins (1-5 mg/day
of folic acid, 10mg/day of B6, and 0.4 mg/day of B12).
ALL vitamin supplements, with the exception of vitamin B12
supplement, are chemically synthesized. This means that
they are produced by combining separate chemical elements
in a factory. Vitamin B12 is biosynthesized, which means
that it is made by using bacterial enzymes.
Also called cobalamin. See also: Barker, Horace Albert.
Last Editorial Review: 9/12/2004
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