Vitamin B12

Essential Micronutrient



Vitamin B12 is one of the most intriguing vitamins and also one of the most complex. It plays many critical roles in our bodies, including maintenance of our nervous systems, formation of red blood cells, energy metabolism, and the proper functioning of our brains. Its importance to our bodies’ optimal performance defines the meaning of the word “essential.”

Other names for Vitamin B12

cobalamin, cyanocobalamin, hydroxycobalamin

Where to find Vitamin B12

The richest concentrations of B12 are in the liver, brain, and kidneys.

Food sources include egg yolks and dairy products as well as seafood such as clams, oysters, salmon, herring, and mackerel.Other meats, such as chicken, turkey, and beef, contain lower levels.

Note: B12 is found in significant amounts only in animal proteins or animal-derived foods such as listed above.

Because B12 is bound to the protein in foods, it must be released by the acids in our stomachs. Thus, people who have lower amounts of stomach acid may not absorb enough B12 from the foods they eat.

Popup: Foods highest in Vitamin B12

Daily Value

The Daily Value for Vitamin B12 is 6 mcg.


Why athletes use Vitamin B12

Vitamin B12 has long been held in high regard for its purported capacity to increase energy, and while this claim is largely anecdotal, there is no disputing the potentially crippling effects on performance and energy that a B12 deficiency could produce. While serious deficiencies are not a common occurrence in normally healthy people, an athlete’s body is taxed by intense workouts and dietary modifications that prevent the comparison to the “average” adult.

While available as an individual vitamin supplement, sufficient B12 can be gained from a complete Vitamin B complex. Given the increased stresses on the bodies of athletes in intense training, this should provide a good “insurance” level.

Ways that Vitamin B12 can enhance Energy & Endurance:
  • Play an essential part in the production of energy by aiding in the use of proteins, carbs, and fats
Ways that Vitamin B12 can enhance Longevity:
  • Play a part in the formation of red blood cells
  • Help keep our nervous systems operating properly


Signs of Vitamin B12 deficiency

Deficiency of Vitamin B12 has been linked to:

  • Fatigue/Weakness
  • Decreased sensory perceptions
  • Neurasthenia
  • Diminished reflex response
  • Mood changes
  • Cognitive dysfunction
  • Amenorrhea (lack of menstrual flow)
  • Pernicious anemia
Potential uses for Vitamin B12

Research indicates that Vitamin B12 may also be useful in the treatment of:

  • Obesity
  • Chronic fatigue syndrome (CFS)
  • Neuritis
  • Menopause
  • Premenstrual syndrome (PMS)
  • Cardiovascular disease
  • Osteoporosis
  • Pernicious anemia


More about Vitamin B12

Vitamin B12 is one of the most intriguing vitamins and also one of the most complex. Its role in the operations of our bodies is diverse — from maintaining the nervous system, red blood cells, and energy metabolism to the proper functioning of our brains, hearts, livers, and kidneys to being a building block of DNA. Clearly, it is essential for optimal health, performance, and well-being.

Supporting optimal health

A necessity for our nervous systems to function properly, Vitamin B12 nourishes the outer covering of our nerves called the myelin sheathe, promoting healthy conduction of energy throughout the entire nervous system. By protecting our nerve cells, B12 indirectly influences our ability to see, hear, think, and move — for life. Speaking of life, B12 aids in the normal formation of the substance that keeps life flowing within: the red blood cells that carry oxygen throughout our bodies.

B12, a red crystalline compound (hence the name “the red vitamin”), also helps metabolize iron, carbohydrates, and fats and is needed for proper digestion and absorption of other nutrients from food. By aiding the formation of the powerful chemical signal in our brains acetylcholine, Vitamin B12 supports memory and learning capabilities as well.

Therapeutic uses

Vitamin B12, in its injectable form, was at one time commonly prescribed for people with chronic fatigue syndrome and showed remarkably positive results when it came to boosting energy levels. No evidence, though, has shown injections to be more effective than oral supplementation, and they’re certainly less pleasant, so they’re rarely used today.


Serious deficiencies of Vitamin B12 are rare in healthy individuals who consume a balanced diet — balanced meaning that it includes meats as a source of protein. Vegetarians clearly do not fall into this range and thus have a much higher occurrence of deficiency, as Vitamin B12 is not found in plants.

There are a few specific conditions that greatly increase the potential of a Vitamin B12 deficiency, such as pernicious anemia, a condition where the body fails to produce a sufficient amount of a protein enzyme that is required to absorb B12.

More common (and treatable) cases of Vitamin B12 deficiency are the result of absorption rates of B12 declining with age. Deficiencies are often seen with the elderly, who may not be eating enough nutritious foods to meet their needs. Thus, the importance of supplementing a healthy diet is increased.

Symptoms of deficiency

Symptoms of Vitamin B12 deficiency may include (among others) a lowered red blood cell count that results in decreased energy levels and a tendency to be easily fatigued, a paleness to the skin, and shortness of breath.

Neurological impairment can include tingling and numbness in the hands and feet in addition to cognitive impairment, including irritability, moodiness, depression, inability to concentrate, and memory lapses.

In conclusion

Just a glimpse at the many vitally important roles Vitamin B12 plays in our bodies’ optimal operation brings a heightened respect for the word “essential.” While I have no plans of running my body low on any essential nutrients, Vitamin B12 is definitely not one I would care to run at or below the deficiency level. And while I have yet to find a direct, scientific connection to B12’s status as the “energy vitamin,” it clearly plays many critical roles in the process of energy and our overall health.



Though requirements are as low as 2 to 4 mcg daily for most adults, significant benefits for those most likely to be deficient, including vegans, are often seen with amounts ranging from 500 to 1,000 mcg daily.

Although available as an individual vitamin supplement, B12 is most often taken as part of a complete B-complex or multivitamin with general dosages ranging from 5 to 100 mcg of B12. Given the increased stresses on the bodies of intensely training athletes, a high-quality B-complex formula should provide a good “insurance” level.


B vitamins are most often taken with meals.

Synergists of Vitamin B12

Optimally taken with all other B vitamins as part of a B-complex.

Vitamin B12 works with folic acid to control homocysteine levels.

Toxicity of Vitamin B12

None known. Well tolerated even at high dosages.

Bans and restrictions

None reported.


  • Carmel, R., “Subtle and Atypical Cobalamin Deficiency States,” Am J Hematol 34.2 (1990) : 108-14.
  • Ellis, F.R., and Nasser, S., “A Pilot Study of Vitamin B12 in the Treatment of Tiredness,” Br J Nutr 30.2 (1973) : 277-83.
  • Pennypacker, L.C., et al., “High Prevalence of Cobalamin Deficiency in Elderly Outpatients” (see comments), J Am Geriatr Soc 40.12 (1992) : 1197-204.
  • Markle, H.V., “Cobalamin,” Crit Rev Clin Lab Sci 33.4 (1996) : 247-356.