Vitamin B12 – Energy Metabolism, Immune & Nerve Function

What is Vitamin B12?

Vitamin B12 is a water-soluble vitamin, naturally present in some foods, fortified in others, available in oral form or as an intermuscular or intravenous injection.  Containing the mineral cobalt, vitamin B12, sometime referred to as “cobalamins”.  Methylcobalamin and 5-deoxyadenosylcobalamin, forms active in the human metabolism, however hydroxycobalamin found to be a stable form that is converted to active form.

What is the function?

Needed to form red blood and immune cells, B12 supports a healthy nervous system as it is required for proper neurological function, as well as DNA synthesis. Without adequate amounts of vitamin B12 absorbed by the body, people began to experience megaloblastic anemia (pernicious anemia) and neurological symptoms such as progressive neuropathy. If repletion of B12 isn’t initiated, permeant degeneration of the nerves and spinal cord may occur.

What happens if I don’t get enough?

The most typical symptom of vitamin B12 deficiency is pernicious anemia. Vitamin B12 plays an important role in proper energy metabolism, immune function, and nerve function. A deficiency results in impaired nerve function, causing numbness, a burning feeling, or a pins-and-needles sensation.  In the elderly, a deficiency causes depression and impaired mental function, mimicking symptoms of Alzheimers’s disease. A deficiency also results in a smooth, beefy red tongue, as well as diarrhea; gastrointestinal disturbance frequently associate with vitamin B12 deficiency.

Deficiencies Correlated with Disease Conditions

Adrenal Fatigue

Vitamin B12 shifts the circadian rhythm of cortisol secretion back to normal, thus alleviating one of the major symptoms caused by adrenal fatigue – insomnia.


B vitamins, B1, B2, B3, B5, B6, B12 and Folate are cofactors in the mitochondrial respiratory chain. The B vitamin cofactors are necessary for converting food into energy and may help with weight loss.

Female Fertility

Pyridoxine (B6) and Vitamin B12 converts toxic homocysteine to a benign form. Lower levels of homocysteine result in better chances of becoming pregnant.

Gastrointestinal Health

Medications for dyspepsia such as, Pepcid, Prilosec, Prevacid, or Zantac either decrease absorption of B12 or deplete existing B12 stores. Also, supplementing with vitamin B12 may improve some individuals complains of dyspepsia.

Supplementation is appropriate in many conditions:


Many people with HIV have a vitamin B12 deficiency, perhaps due to decrease intake, reduced absorption, or as a result of HIV medication. For these patients, it is important to maintain nutritional status for immune function support.


Common in psychiatric disorders, depression maybe an indication of B12 deficiency. Evidence suggest that mental symptoms of depression and fatigue are detectable before anemia develops. Therefore, correcting an underlying deficiency results in a dramatic improvement in mood.


B12 deficiency if common because most people who are diabetic take Metformin. Metformin depletes vitamin B12. Also, similar to the classic symptom of deficiency of impaired nerve function, diabetic neuropathy may respond to supplementation.

Low Sperm Count

Since vitamin B12 is vital for cellular replication, a deficiency results in reduced sperm counts and sperm motility. Supplementation in men with low sperm counts shows significant improvement.

Multiple Sclerosis

The co-existence of a vitamin B12 deficiency in MS may aggregate the disease or promote another cause of progressive demyelination. Above all, methylcobalamin may be the superior form to use in MS.


Constant ringing in your ears? Ringing in your ears or tinnitus could be a result of a deficiency in Vitamin B12. Supplementation could result in some improvement.

Why get a shot or IV when I can simply take an oral supplement?

Vitamin B12, not found in plant food products. Therefore, since dietary sources of cobalamins are strictly from animal food products, those who are vegetarian or vegan may need additional supplementation . Although oral supplementation is possible, the absorption and intracellular activation is often difficult and the injectable form maybe more effective. Because individual who has severe deficiency due to the inability to absorb B12, frequent and larger doses maybe required intramuscular or the intravenous route.


Murray, M. T. (1996). Encyclopedia of nutritional supplements: The essential guide for improving your health naturally. Rocklin, CA: Prima Pub.

NIH Office of Dietary Supplements: Vitamin B12 Fact Sheet for Health Professionals.


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