VITAMIN B12 (CYANOCOBALAMIN)
Vitamin B12 is characterized by the prescence of cobalt. The active forms of
coenzyme vitamin B12 are methylcobalamin and deoxyasdenosylcobalamin.
Vitamin B12 and folatre work to function each other. Just like folate needs
vitamin B12 to function, vitamin B12 needs folate to function. The folate
functions to donate a methyl group to activate the vitamin B12 coenzyme.
Vitamin B12 functions to breakdown amino acid and fatty acids and also
functions in the synthesis of DNA and RNA. Vitamin B12 also serves
to maintain the myelin sheath that surrounds and protects nerve fibers, which
becomes very important in alleviating neuropsychiatric disorders and
prevention of mental deterioraton. Vitamin B12 also has an effect on bone
cell activity and metabolism.
Vitamin B12 is taken through the diet by the proteins to which it is attached.
The vitamin B12 is released from these proteins when it comes in contact
with hydrochloric acid and the pepsin in the stomach. The vitamin is then
absorbed from the intestine and brought into the blood stream. Interestingly
vitamin B12 is one of the only nutrients found in animal derived foods. Strict
vegans should take some form of vitamin B12 supplementation because
although some plant products claim to have vitamin B12, it is not in the
active form. However if vitamin B12 foods are not being consumed it would
take years to develop a deficiency because the body conserves its supply.
R.D.A.
Adults 2 ug/day (.002 mg)
Sources
-Meats
-Fish
-Poultry
-Shellfish
-Milk
-Eggs
-Cheese
Deficiency--Pernicious anemia
It is difficult to acquire low amounts of Vitamin B12 in the body so a deficiency may not reflect poor
intake but it may be from poor absorption. The body not being able to absorb vitamin B12 would mean a
lack of hydrochloric acid or a glycoprotein that attaches to vitamin B12 and aids in absorption. People
who suffer from gastritis would most likely begin to develop a deficiency because of a low level of
hydrochloric acid. Pernicious anemia, which is the deficiency disease of vitamin B12, is caused by the
abscence of the specific glycoprotein, which aids in the absorption of Vitamin B12. In such cases vitamin
B12 must be intramuscularly injected to bypass digestion.
Vitamin B12 Deficiency
Vitamin B12 deficiency may be underestimated in the general population. High-risk groups for the
deficiency syndrome include the elderly, patients taking ulcer medications over long periods, patients with
acquired immunodeficiency syndrome, vegetarians, patients who have undergone stomach resection or
small bowel resection, or both, and patients with dementia. The vitamin B12 deficiency syndrome is
characterized by five stages, the fifth of which results in irreversible neuropsychiatric manifestations.
Although the deficiency is easily treated, diagnosis is somewhat complicated by the shortcomings of the
various tests. Current state-of-the-art testing uses serum cobalamin levels as a screening test and serum or
urine homocysteine and methylmalonic acid determinations as confirmatory tests. Vitamin B12 deficiency
is treatable with monthly injections, large doses of daily oral supplement tablets, or an intranasal gel, which
is far better absorbed than comparable oral supplements.
Vitamin B12 and Folate
Dietary cells and the vitamins B12 and folate are necessary for the production of the red blood cells
(erythrocytes), which carry oxygen from the lungs to the tissues and carbon dioxide from tissues to lungs.
Deficiency of either one results in anaemia, which is characterised by low haemoglobin concentration.
Symptoms result from reduced tissue oxygenation and include weakness, lethargy, palpitation, headache
and shortness of breath. The first-time laboratory test of all patients suspected of being anaemic is the full
blood count. Results of a full blood count may suggest the anaemia is caused by a nutritional deficiency of
B12 folate or iron. Laboratory measurement of the concentration in blood of iron and vitamin B12 and
folate, along with several other tests described here, are useful in the differential diagnosis of the anaemic
patients
Vitamin B12 Deficiency with vegetarians
A nutritional analysis was conducted on the dietary intake of a group of 6 vegan children aged 7 to 14 who
had been living on a vegan diet including brown rice for from 4 to 10 years, and on that of an age-matched
control group. In addition, their serum vitamin B12 levels and other data (red blood cell count, hematocrit,
hemoglobin, etc.) were determined in the laboratory. In vegans' diets, 2-4 g of nori (dried laver), which
contained B12, were consumed daily. Not a single case of symptoms due to B12 deficiency was found.
There were no statistically significant differences between the two groups with respect to any of the
examination data, including B12 levels (p < 0.05). Therefore, consumption of nori may keep vegans from
suffering B12 deficiency
Effects of B12 on the elderly
In a prospective, multicentre, double-blind controlled study, the effect of an intramuscular vitamin
supplement containing 1 mg vitamin B12, 1.1 mg folate, and 5 mg vitamin B6 on serum concentrations of
methylmalonic acid (MMA), homocysteine (HCYS), 2-methylcitric acid (2-MCA), and cystathionine
(CYSTA) was compared with that of placebo in 175 elderly subjects living at home and 110 in hospital.
Vitamin supplement and placebo were administered eight times over a 3-week period. Vitamin supplement
but not placebo significantly reduced all four metabolite concentrations at the end of the study in both study
groups. The maximum effects of treatment were usually seen within 5-12 days. Initially elevated metabolite
concentrations returned to normal in a higher proportion of the vitamin than of the placebo group: 92% vs
20% for HYCS; 82% vs 20% for MMA; 62% vs 25% for 2-MCA; and 42% vs 25% for CYSTA. The
response rate to vitamin supplements supports the notion that metabolic evidence of vitamin deficiency is
common in the elderly, even in the presence of normal serum vitamin levels. Metabolite assays permit
identification of elderly subjects who may benefit from vitamin supplements