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VITAMIN 12 (Cyanocobalamin)

Essential to the metabolism of amino acids, carbohydrates and fatty acids and important for the proper function of the nervous system and the maintenance and formation of blood cells, vitamin B12 is synthesised only by microorganisms in the colon and is not present in many plants and it is bound to the protein in foods. This is a primary reason why most plant-based foods cannot be relied upon to supply good amounts of vitamin B12 except for ashitaba and barley grass which are a surprisingly rich sources of this vitamin.

Most animals obtain the vitamin preformed from their natural bacterial flora and though the bacteria in the human colon produces some B12, because it is below the ileum where B12 is absorbed into the blood stream, it must also be obtained in the diet from the food sources below.

Vitamin B12 stimulates appetite, promotes growth and releases energy. It is often used with older people to give an energy boost, assist in preventing mental deterioration and helps with speeding up thought processes. Some people are also of the opinion that it helps with clearing up infections and provides protection against allergies, cancer and degenerative disorders like Parkinson's disease, Alzheimer's disease and dementia.

The relationship between vitamin B12, vitamin B9 (foliate) and iron is a good example of the complex way in which some essential nutrients help keep the body healthy. Vitamin B12 is indirectly responsible for raising the blood iron level to keep it in a healthy range. Vitamin B12 activates an enzyme called methionine synthase that has many essential functions, including helping the body use vitamin B9 (foliate), which is needed for production of new DNA during cell division. Normally, about one percent of the red blood cells in the circulation are replaced by new cells each day, so that their number always remains adequate to provide oxygen to all cells, tissues and organs. If vitamin B-12 is lacking, usable vitamin B9 can become low, slowing production of new red blood cells in the bone marrow. Eventually, this problem can lead to low levels of iron in the blood as old red cells wear out and die but are not effectively replaced.

Another major function of vitamin B12 involves its participation in the development of nerve cells. A coating which encloses the nerves, called the myelin sheath, forms less successfully whenever B12 is deficient. Although the vitamin plays an indirect role in this process, consumption of foods rich in vitamin B12 has been shown to be effective in relieving pain and other symptoms in a variety of nervous system disorders.

Deficiency of vitamin B12

Vitamin B12 is closely related to nerve health and keeps the mind sharp when aging. A lack of this essential vitamin may shrink the brain. Lack of concentration, mental fogginess and having problems with memory are all important signs that may indicate a B12 deficiency.  Because it can also result in the raising of the level of homocysteine in the blood which, in high doses, can be toxic to the brain, vitamin B12 deficiency may also be involved in Alzheimer's and Parkinson's disease. Another health issue that can occur is the eroding of the myelin sheath which is the fatty sheath of tissue that insulates the nerve fibres in the body.

Older adults with atrophic gastritis hampers the ability to absorb vitamin B12 from natural foods. Athletes, alcohol drinkers, people in stressful situations, people taking recreational or prescribed drugs, pregnant and lactating women, those on low-fat or meat free diets, vegetarians and vegans, people with food allergies, especially to wheat, and those that have parasite infections can all become deficient in vitamin B12. Severe deficiency may result in pernicious anaemia also called Addisonian pernicious anaemia.

If vitamin B12 deficiency is suspected and there are no resources to measure cellular vitamin B12 levels, then checking the blood levels of methylmalonic acid can help with assessing vitamin B12 requirements as it increases with declining vitamin B12 activity.

Other symptoms of vitamin B12 deficiency can include:

  • Apathy and lethargy

  • A sore tongue

  • Back pain

  • Decreased reflexes

  • Fatigue

  • Loss of balance

  • Tingling fingers and toes

  • Tinnitus (ringing in the ears)

  • Weakness

  • Weight loss


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Vitamin B12 sources

Fungi, plants and animals are incapable of producing vitamin B12. Only bacteria and archaea have the enzymes required for its synthesis, although many foods are a natural source of B12 because of bacterial symbiosis. Vitamin B12 is stored in the liver and secreted in the bile as a coenzyme.

Re-absorption takes place in the body and, as long as there are no digestive/absorption issues or liver disorders, both meat eaters and vegetarians will gain enough from a balanced and varied diet which includes raw organically grown vegetables and seeds and nuts which contain vitamin B12 from microbial action in the soil.

Root vegetable with stained spots due to contact to soil, are a good supply of vitamin B12 however, once they are peeled or scrubbed they will no longer contain any vitamin B12. Barley grass is one very good plant source of vitamin B12.

Highest sources of vitamin B12 in micrograms per 100 grams

  • Clams 98.9 μg

  • Liver 83.1 μg

  • Barley grass juice 80 μg

  • Nori seaweed 63.6 μg

  • Octopus 36 μg

  • Caviar/fish eggs 20.0 μg

  • Ashitaba (dried powder) 17.0 μg

  • Herring 13.7 μg

  • Tuna fish 10.9 μg

  • Crab 10.4 μg

  • Mackerel 8.7 μg

  • Lean grass fed beef 8.2 μg

  • Duck eggs, goose eggs, rabbit 6 μg

  • Crayfish, pork heart, rainbow trout 5 μg

  • Shiitake mushrooms 4.8 μg

  • Lobster 4 μg

  • Lamb, venison 3.7 μg

  • Swiss Cheese 3.3 μg

  • Salmon 3.2 μg

  • Whey powder 2.37 μg

  • Golden chanterelle mushrooms 2 μg

  • Tuna 1.9 μg

  • Halibut 1.2 μg

  • Chicken egg 1.1 μg

  • Chicken, turkey 1.0 μg

  • Anchovies 0.9 μg

  • Ashitaba leaves 0.4 μg

NOTE: One μg is one microgram. The daily recommended amount for an averagely active adult is 2.4 μg daily.

Vitamin B12 toxicity

Supplements are not advised, unless blood tests show a deficiency, as excessive consumption of vitamin B12 can cause arthritis, anxiety, back pain, coronary artery spasms with chest pains, diarrhoea, headaches, indigestion, lack of coordination, nausea and vomiting, nervousness, numbness or pain down the right arm, swelling and/or tingling or numbness on the right side of the face,  .

There is also a risk of hypokalaemia (low potassium), pulmonary oedema, peripheral vascular thrombosis and optic nerve atrophy for someone with Leber's disease. Leber's hereditary optic neuropathy (LHON) or Leber optic atrophy is a mitochondrially inherited (transmitted from mother to offspring) degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision and mainly affects young adult males.

Risks from intranasal use of vitamin B12 include glossitis, headaches, rhinitis, sore throat and a feeling of pins and needles. Individuals suffering from mitral valve prolapse (MVP) are also liable to experience a worsening or an acute flare-up of MVP symptoms following a vitamin B12 shot.

Pins and needles, tingling and numbness in the tips of fingers and toes can develop from vitamin B9 deficiency which can be caused by ongoing high vitamin B12 supplementation or injections  Levels of vitamin B9 must always be checked when high levels of vitamin B12 are taken.

Vitamin B15 and coenzyme Q10 can counteract high levels of vitamin B12.

 Related articles

External references

  • University of Michigan. Vitamin B-Complex. http://www.uofmhealth.org/health-library/hn-2922005

  • Office of Dietary Supplements. Vitamin B12. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

  • Office of Dietary Supplements. Vitamin B6. https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/

  • Office of Dietary Supplements. Thiamin. https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional

  • University of Maryland. Vitamin B2 (Riboflavin). http://umm.edu/health/medical/altmed/supplement/vitamin-b2-riboflavin

  • University of Maryland Medical Center. Vitamin B3 (Niacin). http://www.umm.edu/health/medical/altmed/supplement/vitamin-b3-niacin

  • Daul, A. & Beuhler, M. (2011). Niacin toxicity resulting from urine drug test evasion. https://www.ncbi.nlm.nih.gov/pubmed/20138459

  • The Mayo Clinic. Vitamin B6 (pyridoxine). http://www.mayoclinic.org/drugs-supplements/vitamin-b6/safety/hrb-20058788

  • Sharp, A. & Fedorovich, Y. (2015). Teratogenic effects of pyridoxine on the spinal cord and dorsal root ganglia of embryonic chickens.

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