Vitamin B12 : An Essential Part of Your Life


Structure of the adenosylcobalamin form of vitamin B12

Vitamin B12 bound within the binding clef of intrinsic factor


About the Site 

This site contains general information about vitamin B12, including its structure, absorption, uses within the body, dietary sources of vitamin B12, and its association with many diseases, including Atrophic gastritis, inflammatory bowel disease, neuritis, diabetes, multiple sclerosis, dementia and Alzheimer's Disease. The majority of the information is sourced from scientific publications, which can be found by clicking the <Publications> link at the bottom of the relevant pages.

Vitamin B12

Vitamin B12 (cobalamin), has a deep red colour and is an important member of the B group water soluble vitamins. It has a key role in the functioning of the brain and nervous system and in the formation of red blood cells. Severe lack of vitamin B12 can result in anemia, whilst even a moderate continued lack has been associated with several conditions including neuritis, multiple sclerosis, cognitive impairment, dementia and Alzheimer's disease. Vitamin B12 has a central cobalt atom (in pink on the structure model), to which are attached different functional groups, which lead to different forms (vitamers) of the vitamin depending upon the group. In the body the two main forms are adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), which are each used by a different set of enzymes within the cell. The majority of injected vitamin B12 preparations, supplements, or food additives have a synthetic  form of vitamin B12 called cyanocobalamin that does not occur in nature. Technically cyanocobalamin is not a vitamin as it is biologically inert and has to be converted to the active form in the body, with the release of toxic cyanide.

Absorption of Vitamin B12 

Absorption of vitamin B12 from the intestine requires that it be released from food through the action of various enzymes in the intestine. It then must be bound by a specific transport protein, called intrinsic factor which is released in the stomach. Patients who are deficient in intrinsic factor, or who have antibodies against intrinsic factor can become deficient in vitamin B12.  The capacity of the vitamin B12- intrinsic factor mediated uptake is very limited and in humans it is only possible to absorb 1-1.5 ug of vitamin B12 per feed. Absorption of vitamin B12 can be severely impaired in patients who have intrinsic factor deficiency or who may gastro-intestinal problems, such as gastric ulcers, atrophic gastritis, Crohn’s Disease and Ulcerative Colitis. Vitamin B12 deficiency can be a serious complication of Meformin use in people with diabetes.

Vitamin B12 Deficiency

The development of vitamin B12 deficiency is a slow and insidious process, which may take several years to manifest itself. During this time there can be progressive loss of vitamin B12 in the cerebrospinal fluid (CSF), which precedes overt deficiency as measured in serum, and without anaemia or macrocytosis. Deficiency of the vitamin in the CSF can lead to brain atrophy and subacute combined degeneration of the spinal cord, cerebrovascular disease, an increased incidence of cancer sores. Vitamin B12 deficiency can occur after bowel resection, or gastric by-pass surgery. Vitamin B12 deficiency can occur due to atrophic gastritis, a condition that effects 10-30% of the elderly. Other causes of vitamin B12 deficiency include achlorhydria, ageing, excessive antibiotics or anti-convulsants (often used in persons with epilepsy), gastrectomy, especially of the cardiac or fundus, liver disease or cancer,  megadoses of vitamin C and/or copper, pregnancy, intestinal parasites such as giardia, fish tapeworms, a primarily vegan diet, certain religions, such as 7th Day Adventists, rastafarians, and excessive smoking. Vitamin B12 deficiency in the elderly has been associated with an unstable gait, numbness and tingling in the hands and feet, urinary incontinence, hearing loss and an increased incidence of bone facture. Vitamin B12 deficiency has also been associated with the use of the following drugs, cholestyramine, cymetidine, clofibrate, colchicine, methotrexate, methyldopa, neomycin, omeprazole, some oral contraceptives, phenobarbital, ranitidine, tetracyclines, valproic acid, anti-epileptic drugs (carbamazipine and others) and zidovudine (AZT).  Vitamin B12 deficiency in pregnant mothers is associated with an increased incidence of neural tube defects in the young. Once a person is deficient in vitamin B12, it is almost impossible to overcome this deficient through dietary supplementation, particularly if the underlying cause is not removed/cured. Thus persons who are deficient normally require regular injections of vitamin B12, Recently it has been found that it is possible to obtain vitamin B12 through application to the skin using specialized topical technology described in this site.

Vitamin B12 - Definition of deficiency - levels in serum

In the USA and Australia, normal levels of vitamin B12 have been determined to be in the range 180-750 pmol/L (244-1017 pg/ml), with vegans normally much lower at around 110 pmol/L, being regarded as deficient. Recently, many studies looking at biological markers of vitamin B12 deficiency (MMA and Hcy) as well as neurological markers of deficiency, have suggested that deficiency may start at 300 pmol/L (406 pg/ml), which is also regarded as the lower level of the normal range by the Japanese health authority. It is estimated that as many as two thirds of the people who are in the lower range of serum vitamin B12 levels (190-300 pmol/L) may have functional vitamin B12 deficiency (see PDF). Vitamin B12 deficiency can result in the following conditions ataxia, achlorhydria, pernicious anemia, confusion, depression, disorientation, fatigue, glossitis, impaired lymphocyte response, memory loss, decreased libido, low sperm count, erectile dysfunction, low testosterone, increased rate of miscarriage in women,  psychoses, paresthesia, progressive peripheral neuropathy with pronounced anemia, spinal degeneration, brain atrophy, dementia, cognitive decline and macrocytic cells. Vitamin B12 levels in the subclinical low-normal range (<250 ρmol/L) are associated with Alzheimer's disease, vascular dementia, and Parkinson's disease. Vegetarianism and Metformin use contribute to decreased  vitamin B12 levels and may independently increase the risk for cognitive impairment. Vitamin B12 deficiency (<150 ρmol/L) is associated with cognitive impairment. Low vitamin B12 levels have also been associated with multiple sclerosis,.

Pregnant women with vitamin B12 levels below 250 pmol/L have twice the incidence of children with neural tube defects than those with higher levels.

Post menopausal women with low levels of vitamin B12 have been shown to have a higher risk of breast cancer (see )

Subclinical deficiency in vitamin B12 (<250 pmol/L) can be monitored by rises in the level of homocysteine (Hcy) (>10 umol/L) and methylmalonic acid (>200 noml/L). Increased levels of Hcy is associated with vascular inflammatory disease and  increases in cardiovascular disease, whilst increases in MMA can result in destruction of the myelin sheath around neurones.

Therapeutic use of Vitamin B12 

Vitamin B12 has been used in therapy for many conditions including AIDS/HIV support, anemia, anemia of pregnancy, pernicious anemia, asthma, atherosclerosis, allergies, atopic dermatitis, contact dermatitis, psoriasis, seborrheic dermatitis, bursitis, sciatica, canker sores, chronic fatigue syndrome, Alzheimer’s disease, dementia, depression, Crohn’s disease, diabetes mellitus, diabetic neuropathies, neuralgias, post-herpetic neuralgia, diabetic retinopathy, fatigue, herpes zoster, high cholesterol, high blood  homocysteine levels, insomnia, male infertility,   tinnitus, viral hepatitis, and vitiligo

Prevention and Treatment of Vitamin B12 insufficiency

Vitamin B12 insufficiency can be prevented either by adherence to a diet that is sufficient in vitamin B12 (see link), by the use of supplements, by injection of vitamin B12 or via topical administration of vitamin B12. Persons who are deficient due to poor absorption, or through conditions affecting absorption require regular vitamin B12 supplementation either via vitamin B12 injections or  by regular application of topical vitamin B12.

Vitamin B12 in Supplements

The use of vitamin B12 in supplements for treatment of deficiency is controversial with many studies showing no benefit being obtained from standard supplements as the amount of vitamin B12 in the standard supplements is too low, and because almost invariably the supplement contains cyanocobalamin (a synthetic pro-vitamin) rather than adenosylcobalamin or methylcobalamin, the two natural forms of the vitamin. Furthermore, studies with high dose oral supplements with cyanocobalamin were not effective in restoring normal levels of homocysteine or methylmalonic acid, in reversing clinical signs of deficiency, or in maintaining normal levels of serum vitamin B12 once supplements were ceased. In addition, high dose oral supplements have NOT been shown to be able to increase the concentration of vitamin B12 in the cerebral spinal fluid, or the brain.

Vitamin B12 Injections

Vitamin B12 injections can be administered in cases of insufficiency, however these are generally expensive, must be given by a medical practitioner, are painful and like oral supplements, invariably contains cyanocobalamin (a synthetic pro-vitamin) rather than adenosylcobalamin or methylcobalamin, the two natural forms of the vitamin. In some countries such as Europe and South America both the methyl and adenosyl-vitamin B12 forms of the vitamin are available for injection. Injections must be given every 4 to 6 weeks, as they do not seem to overcome deficiency, but merely provide a temporarily boost in circulating levels of vitamin B12

Topical Vitamin B12

A topical form of vitamin B12 has recently been developed. This preparation is easy to administer, contains the natural form of the vitamin, is able to deliver therapeutic amount of vitamin B12 and has the added advantage of providing a prolonged release of the vitamin over several days.  This prolonged release potentially allows for continuous loading of the various organs including the liver and more importantly the CNS and brain.

Further Information on Vitamin B12 and its uses

Further information on vitamin B12 and deficiency states, as well as potential use of vitamin B12 can found by following the links. NIHPDF PDF


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