Everything You Need To Know About Vitamin B-12
What Is Vitamin B-12?
Vitamin B-12 is the most complex of the B-vitamin family. It has different forms: cyanocobalamin, hydroxocobalamin, adenosylcobalamin and methylcobalamin, with only the last two being involved in metabolic functions in the human body. Hydroxocobalamin is produced by bacteria and is used to treat cyanide poisoning. 
The US Food and Drug Administration (FDA) has set the Recommended Daily Value (RDV) for B-12 at 6 mcg (micrograms).  It is essential that the required amount of this very important vitamin is obtained, as it is needed for proper functioning of the brain and nervous system as well as for the synthesis of DNA and RNA.
The most common absorption mechanism of B-12 from whole foods is to first unbind the vitamin from proteins; this reaction is carried out in the stomach by hydrochloric acid and gastric protease. If vitamin B-12 is taken as a supplement or obtained from fortified foods this step is not necessary, as it is already in the free form. The second step in this process is combination with glycoproteins formed in the stomach to make a compound absorbed by the small intestines.
The human body stores several years’ worth of vitamin B12 in the liver, so low levels in the body are rare. Decreases in vitamin B12 levels are more common in the elderly, HIV-infected persons, and vegetarians. (MayoClinic.org) 
People with gastrointestinal disorders and those who have had gastrointestinal surgery are most likely to suffer from vitamin B-12 deficiency. Other persons at risk of deficiency are pregnant and lactating women who are vegetarians (or vegans), and those suffering from pernicious anemia.
When sufficient amounts of vitamin B-12 are not obtained, vitamin B-12 deficiency results, characterized by anemia (a deficiency of red blood cells, the oxygen carriers), fatigue, weakness, constipation, loss of appetite, and neurological changes such as numbness and tingling in the hands and feet. Other symptoms include depression, dementia, memory loss, and the inability to maintain one’s balance. 
Vitamin B-12 may be obtained from whole foods listed below, fortified foods, and dietary supplements.back to menu ↑
Facts About Vitamin B-12
- Fungi, plants, and animals are incapable of producing vitamin B-12. Only bacteria or single-celled microorganisms have the enzymes necessary to fully synthesize vitamin B-12.
- Vitamin B-12 is also known as cobalamin.
- Vitamin B-12 can only be produced commercially through bacterial fermentation.
- Vitamin B-12 is the largest and most complicated of the B vitamin in terms of structure.
- All the forms of vitamin B-12 are red, due to the cobalt-corrin complex present.
- Feces is a very rich source of vitamin B-12; therefore dogs, cats and rabbits eat it.  
Foods Containing Vitamin B-12
Vitamin B-12 may be obtained from a variety of whole foods, such as:
- beef tenderloin
- beef and chicken liver
- some seafood: salmon, herring, mackerel, sardine, tuna, trout, crabmeat, fish eggs, clams
More processed sources of the vitamin include fortified breakfast cereals, energy bars, soy products and nutritional yeast.
Vitamin B-12 is also available as a dietary supplement, either as an over-the-counter multivitamin or as an intravenous prescription. Supplemental forms of the vitamin are cyanocobalamin, methylcobalamin, and adenosylcobalamin, while as a prescription medication it is in the form of cyanocobalamin and hydroxocobalamin to be administered as an injection. There is also a gel formula, which is administered in the nasal passage as an alternative to the injection.
NOTE: From TheVeganSociety.com: “The only reliable vegan sources of B12 are foods fortified with B12 (including some plant milks, some soy products and some breakfast cereals) and B12 supplements. Vitamin B12, whether in supplements, fortified foods, or animal products, comes from micro-organisms.” back to menu ↑
Benefits of Vitamin B-12
Chief among the numerous benefits of vitamin B-12 is maintaining a healthy heart and reducing heart disease. Vitamin B-12 reduces the homocysteine levels, a contributing factor in heart disease.
Energy Maintenance in the Body
Vitamin B-12 reduces symptoms such as fatigue and weakness.
Possible Aid in Neurological Maintenance
Additionally, vitamin B-12 may help in the treatment of neurological diseases as well as help to enhance the normal functioning of the nervous system. Vitamin B-12 is needed for the synthesis of certain compounds which are critical in dealing with depression and mood regulation.
Maintains Healthy Hair, Skin, Nails
Vitamin B-12 enables the production of cells. It alleviates symptoms associated with skin conditions such as eczema and psoriasis.
Vitamin B-12 is needed for the production of red blood cells, reducing the risk of anemia.
Fetal Genetic Development
A very important function of vitamin B-12 is that it is needed for the synthesis of DNA, the genetic building block of all newborns. It is therefore vital for the development of healthy, normal growth in infants. This is why pre-natal vitamins contain vitamin B-12 and are recommended by most obstetricians during pregnancy and nursing. back to menu ↑
Is Vitamin B-12 Ever Bad For You?
The Institute of Medicine of the National Academies has not set an upper intake limit for vitamin B-12 as it has very little potential to be toxic and has no adverse effects even when taken at doses in excess of its recommended daily intake. Two trials (NORVIT and HOPE 2) conducted indicate that at doses well over the RDV for extended periods of time there were no adverse effects experienced. The NORVIT trial had participants on a dosage of 0.4mg for 40months and HOPE 2 trial utilized a dosage of 1mg for 5yrs; no adverse reactions were reported.
|Age/Gender/Condition||Recommended Daily Value (RDV)|
|infants to 12 months||0.4 – 0.5 mcg|
|children 1- 8 years||0.9 – 1.2 mcg|
|Youth 9 – 13 years||1.8 mcg|
|14 years and up||2.4 mcg|
Currently there is no evidence of adverse reactions—aside from direct allergy to B-12 or to cobalt—associated with intake of vitamin B-12 either from food sources or dietary supplements. But there are a few recommended precautions.
One precaution is regarding interactions with other drugs; vitamin B-12 reacts with Chloramphenicol, an antibiotic; the reaction causes a reduction in the formation of red blood cells. Other drug interactions are with Prilosec, Zantac and Metformin; all decrease the absorption of vitamin B-12, thereby increasing the possibility of vitamin B-12 deficiency. The Mayo Clinic adds a few more items to that list of substances that interfere with B-12 absorption. 
The other precaution involves pre-existing medical conditions. The Mayo Clinic urges caution with B-12 in people with the following conditions (detailed on the link): 
- Heart concerns
- Hypertension (high blood pressure)
- History of cancer
- Skin disorders
- Genito-urinary concerns
- Gastrointestinal concerns
- Blood disorders
- Low potassium levels
- History of gout
- Leber’s disease: may lead to damage of the optic nerve and eventually blindness. 
How To Minimize Exposure
There is no real need to minimize one’s intake of this very important vitamin, though gaining it through food sources is better for the body as a whole.back to menu ↑
Should You Worry About Vitamin B-12?
Aside from the precautions above, there is no need for otherwise healthy individuals to worry about their B-12 intake.back to menu ↑
Vitamin B-12 is very important to the overall health and well-being of an individual, with functionality in DNA synthesis, formation of red blood cells, cardiovascular maintenance, brain function, and nerve function.
It is highly recommended that adequate intake of this vitamin be obtained by eating foods rich in vitamin B-12. For people who are vegetarians or vegans, it is highly recommended that they incorporate a supplemental form of this vitamin in their diet, as most of the foods rich in this vitamin are meat sources.
Persons suffering from particular diseases such as pernicious anemia or any sort of gastrointestinal disorder should ensure that they obtain vitamin B-12 as an intravenous dietary supplement, since absorption of B-12 is severely curbed in these instances. Your health care provider should be fully informed of any gastrointestinal problems, as well as any previous surgeries done, so that the right type of this vitamin B-12 will be administered.
Due diligence should also be exercised when taking certain medications in conjunction with vitamin B-12, due to its propensity to interact with some drugs—these interactions may result in vitamin B-12 deficiency and serious health effects. Although there have been no adverse effects associated with high intake of vitamin B-12 in healthy individuals, from either food sources or supplements, precautionary measures should still be taken as cases of allergic reactions have been reported.
If you are pregnant or breastfeeding it is critical that you discuss with your health care provider the best option available for obtaining the correct amounts of vitamin B-12, as deficiency may result in serious health problems in the fetus or newborn.