Vitamin B12 (Cobalamin)


This vitamin is also known as cobalamin and until recent times nobody paid too much attention to it.  It was known to be needed for healthy red blood cells, but unless a person had anemia, vitamin B12 was overlooked.  One reason for this disinterest was that the RDA is the smallest for any vitamin.

Even that tiny amount (just a few mcg - is essential and not just for blood but for several other functions, including keeping the mind sharp, preventing heart disease and allowing the immune system to work properly.

Why People Need Vitamin B12

Cobalamin's most important role is making red blood cells healthy. When a person gets enough cobalamin the body can produce millions of healthy red blood cells every day.  But when a person does not get enough vitamin B12, too few red blood cells are made and the ones that are produced are too large and fragile to work well.  Anemia develops when an individual does not have enough red blood cells to carry oxygen and nutrients around the body.

Not just red blood cells but all the cells need cobalamin to grow and divide properly.  Vitamin B12 is essential for making all the different cells in the immune system, including white blood cells.

Another important function for cobalamin is to make the protective fatty layer or sheath that coats the nerve cells, a little like the insulation on electric wires.  If the sheath becomes damaged because the body does not have enough cobalamin, the equivalent of static in the nerve takes place.  A bad case of "static" can interfere with mental function to the point that others may think the person is senile.

Vitamin B12 works with other B vitamins but functions especially well with folic acid and pyridoxine to help the body turn fats, carbs and proteins into energy for the cells.

Vitamin B12 Requirements

Even though this vitamin is extremely important, the body only needs small amounts of it.  The RDA for an adult is less than 3 mcg.  The problem with this RDA is that it does not take into account that the body absorbs less cobalamin as a person ages.  Many health care practitioners feel people over the age of 50 need much more cobalamin. Some physicians recommend daily supplements containing 500 to 1,000 mcg of B12.

When the Body is Deficient

It can be difficult to know if a person is deficient in cobalamin because it is found only in animal foods (such as liver, eggs, fish and meat) and only in very small amounts that are hard to absorb.  The body needs to be really good at absorbing cobalamin to get the correct amounts.  A special substance in the stomach (called intrinsic factor) helps a person absorb vitamin B12.  Most people take in more than twice the RDA simply through a healthy diet, so the average person typically gets enough.

However, recent research suggests that a vitamin B12 deficiency might be more common than was previously thought.  Middle-aged and older women who are consuming enough cobalamin can still have signs of mild vitamin B12 deficiency.  The problem seems to go away when these women raise their intake of cobalamin by just 6 mcg. 

Other research shows that 39 percent of the population have low to normal levels of vitamin B12 and around 17 percent have levels low enough to be deficient.  Many researchers believe the RDA for all adults (not just elderly people) should be raised to 6 mcg to prevent a deficiency.

Even though cobalamin is a water-soluble vitamin, some of it is stored in the liver and kidneys.  The body is also good at recycling cobalamin so the body stores it very quickly.

If a person stops consuming enough cobalamin in his or her diet, it may take up to 4 or 5 years for the symptoms of a deficiency to begin showing up.  If the body stops producing intrinsic factor, the same thing could happen - it could take several years for symptoms to begin.

Anemia is the most obvious symptom of cobalamin deficiency.  In the case of anemia, this is because the body does not have enough healthy red blood cells.  When anemia is caused by a shortage of vitamin B12, it is called megaloblastic anemia.  Anemia caused by a lack of intrinsic factor is called pernicious anemia.  While the causes are different, the result is the same - the body does not have enough red blood cells.  The ones that are in the body are too fragile and big to survive long.

Typically, most people younger than the age of 50 receive enough cobalamin from their diets, but older people and some others are at risk for a deficiency.  Some of the groups who could be at risk for a vitamin B12 deficiency include:

  • Strict vegetarians and vegans - Because vitamin B12 is found only in animal foods, those people who do not eat these foods can be deficient.  Children can be especially at risk.

  • Those older than the age of 50 - As a person ages, they naturally make less intrinsic factor and absorb less vitamin B12.  The body also produces less stomach acid, which means less cobalamin is released from the food while it is in the stomach.

  • Women who are breastfeeding - The baby takes a lot of cobalamin.  Extra vitamin B12 should be taken through food or supplements.

  • People who smoke cigarettes - Smokers tend to have low levels of cobalamin in their bloodstream, as well as all the other B vitamins.

  • People who take the following drugs: Prilosec, Pepcid, Zantac, and Glucophage, as well as prescription potassium supplements.

Symptoms of Vitamin B12 Deficiencies

Before a person becomes anemic, the following symptoms may be present:

  • Tingling or numbness in the hands and feet

  • Moodiness and depression

  • Memory loss

  • Trouble sleeping

  • Dizziness and loss of balance

  • Dementia

Foods Containing Vitamin B12

Meat, fish and eggs have natural cobalamin.  This vitamin is added to some breakfast cereals.



  1. Alan H. Pressman and Sheila Buff.(2007). The Complete Idiot's guide to vitamins and minerals. New York : Alpha Books
  2. Brewer, S. (2010). The essential guide to vitamins, minerals and herbal supplements. London : Right Way
  3. Elson M. Haas, Md & Buck Levin, Phd, Rd.(2006). Staying Healthy with Nutrition: The Complete Guide to diet and nutritional medicine. Berkeley, Calif. : Celestial Art
  4. Holford, P. (2004). The optimum nutrition bible. London : Piatkus
  5. Holford, P & Lawson, S.(2008). Optimum Nutrition Made Easy How to achieve optimum health. London : Piatkus
  6. Lieberman, S. & Bruning, N. (2003). The Real Vitamin & Mineral Book. New York : Avery
  7. Rodale Health Books.(2009). Healing with vitamins : the best nutrients to slow, stop, and reverse disease. Emmaus, Pa. : Rodale
  8. Royston, A.(2003). Vitamins and minerals for a healthy body. Oxford : Heinemann Library
  9. The National Research Council.(1989). Recommended Dietary Allowances, 10th ed, National Academy of Sciences
  10. Werbach, M. (1993). Nutritional Influences on Illness. 2nd ed. Los Angeles: Third Line Press

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