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vitamin B12

Alternative Names
cobalamin, cyanocobalamin

Vitamin B12 is a water-soluble vitamin. It can dissolve in water. It is one of the B-complex vitamins. The B complex includes:
  • B1
  • B2
  • B6
  • pantothenic acid
  • folic acid
  • niacin
  • biotin
Cobalamin is the general name for vitamin B12.

What food source is the nutrient found in?
Vitamin B12 is found in animal foods, fortified foods, and some fermented foods. Some sources of B12 are:
  • eggs
  • meats
  • poultry
  • fish, seafood
  • dairy products
  • tempeh and miso (both from soy)
  • fortified soy drink
The amount of B12 in some foods include:
  • salmon, cooked (90g) = 2.6 mcg (micrograms)
  • beef tenderloin lean, grilled (90g) = 2.2 mcg
  • milk (1 cup) = 0.5 mcg
How does the nutrient affect the body?
Vitamin B12 helps the body:
  • make red blood cells, with folic acid, another B-vitamin
  • work with many body chemicals that occur in all body cells
  • copy the genetic code within each cell
  • form and maintain the nervous system
  • build and maintain protective coating around nerves
  • digest and use fats, carbohydrates, and some proteins for energy
  • form neurotransmitters in the brain, such as serotonin, that help regulate mood, sleep, and appetite
The recommended dietary intake, or RDI, for vitamin B12 for adults is 2 micrograms (mcg) per day. For pregnant women, the RDI is 3 mcg; for nursing women it is 2.5 mcg. A microgram is a very small amount. Since the only dietary sources of B12 are animal products, strict vegetarians may need to take supplements. They may also eat foods that have had the vitamin added.

Not getting enough vitamin B12 can cause:
  • anaemia
  • fatigue
  • nerve damage, with symptoms such as tingling sensations and numbness
  • sore tongue
  • very sensitive skin
  • muscle and nerve paralysis
  • constipation
Some people have trouble absorbing B12. Other people may just have poor dietary intake. Anaemia can be treated with injections of B12. Strict vegetarians who eat no animal products, their infants, and older people are at the highest risk for vitamin B12 deficiency. For these people, eating fortified foods and/or taking dietary supplements can help prevent a deficiency. High intakes of folic acid can hide anaemia.

Getting too much vitamin B12 has no known symptoms or toxicity. It is stored mainly in the liver. Since it is water-soluble, any extra leaves the body in the urine. There is no proof that taking extra B12 boosts energy. Vitamins do not create energy. They do not provide kilojoules to the body for energy. Vitamins help breakdown nutrients that are energy-yielding. These nutrients include carbohydrate, protein, and fat.

Calcium is necessary for normal absorption of vitamin B12. A deficiency of either iron or vitamin B6 can decrease the absorption of B12.

Author: Kimberly Tessmer, RD, LD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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