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Vitamin B12Page 2 of 2
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Beneficial Effects
Vitamin B12 like folic acid, functions as a "methyl donor." A methyl donor is a compound that carries and donates methyl groups (a molecule of one carbon and three
hydrogen molecules) to other molecules, including cell membrane components and neurotransmitters. As a methyl donor, vitamin B12 is involved in homocysteine metabolism
and plays a critical role in proper energy metabolism, immune function, and nerve function.
Homocysteine is a factor in the progression of both atherosclerosis and osteoporosis. In fact, elevations in homocysteine are an independent risk factor for having a
heart attack. Approximately 20 to 40 percent of patients with heart disease exhibit elevations in homocysteine. In addition to vitamin B12 and folic acid, vitamin B6
is also necessary in metabolizing homocysteine to nondamaging forms. Although research has focused much of its attention on folic acid supplementation as a mechanism
to lower homocysteine levels, the prevalence of suboptimal levels of these nutrients in men with elevated homocysteine levels was 56.8 percent for B12 , 59.1 percent
for folic acid, and 25 percent for B6, indicating that folic acid supplementation alone would not lower homocysteine levels in many cases. Folic acid supplementation
lowers homocysteine levels only if there are adequate levels of vitamin B12 and B6. Because of the interconnectedness of these three B vitamins, it is best to
supplement with all three. Folic acid and vitamin B12 supplementation lowers homocysteine levels even in individuals with normal vitamin B12, folic acid, and
homocysteine levels.
Principal Uses
Vitamin B12 supplementation is appropriate in many conditions, including AIDS, impaired mental function in the elderly, asthma and sulfite sensitivity, depression,
diabetic neuropathy, low sperm counts, multiple sclerosis, and tinnitis.
Dosage Ranges
Vitamin B12 is necessary in only very small quantities, the RDA is 2 micrograms. For oral vitamin B12, the recommended dosage in deficiency states is 2,000 micrograms
daily for at least 1 month, followed by a daily intake of 1,000 micrograms. This dosage schedule is suitable for other clinical applications of vitamin B12 except
high-dose therapy for MS. For vegetarians, a dosage of at least 100 micrograms per day is recommended. Methylcobalamin, the active form of vitamin B12, supplied in
sublingual tablets is preferred over cyanocobalamin.
Safety Issues:
What is the health risk of too much vitamin B12?
Vitamin B12 has a very low potential for toxicity. The Institute of Medicine states that "no adverse effects have been associated with excess vitamin B12 intake
from food and supplements in healthy individuals." The Institute recommends that adults over 50 years of age get most of their vitamin B12 from supplements or
fortified food because of the high incidence of impaired absorption of B12 from unfortified foods in this population.
Available Forms
Vitamin B12 is available in several forms. The most common form is cyanocobalamin; however, vitamin B12 is active in only two forms, methylcobalamin and
adenosylcobalamin. Methylcobalamin is the only active form of vitamin B12 available commercially in tablet form in the United States. While methylcobalamin is
active immediately upon absorption, cyanocobalamin must be converted to either methylcobalamin or adenosylcobalamin by the body to remove the cyanide molecule
(the amount of cyanide produced in this process is extremely small) and add either a methyl or adenosyl group. Cyanocobalamin is not active in many experimental
models, and neither methylcobalamin or adenosylcobalamin demonstrate exceptional activity. For example, in a model examining the ability of vitamin B12 to extend l
ife in mice with cancer, methylcobalamin and adenosylcobalamin led to significant increases in survival time, but cyanocobalamin had no effect. Methylcobalamin
also produces better results in clinical trials than cyanocobalamin. I consider it the best available form.
Interactions
Vitamin B12 and folic acid are intricately involved in chemical processes. Since vitamin B12 works to reactivate folic acid, a deficiency of B12 results in a
folic acid deficiency if folic acid levels are only marginal. A high intake of folic acid may mask a vitamin B12 deficiency because it prevents the changes in
the red blood cells but does not counteract the deficiency in the brain.
Vitamin B12 also influences melatonin secretion. The low levels of melatonin in the elderly may be a result of low vitamin B12 status. Vitamin B12 (1.5 milligrams
of methylcobalamin per day) produces good results in the treatment of sleep-wake rhythm disorders, presumably as a result of improving melatonin secretion.
A great source for this important vitamin is
www.wonderlabs.com.
Good price, excellent shipping.
REFERENCE: Encyclopedia of Nutritional Supplements; by Michael T. Murray, N.D..
I recommend Wonder Laboratories for the
overall best quality and price when considering vitamins, herbs and supplements.
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