Vitamin B12: A HealthCentral Explainer


What is it?

Vitamin B12 is a water-soluble member of the B vitamin family (there are eight B vitamins total). It is the largest and most structurally complex of any vitamin.

What does it do?

In the world of B Vitamins (there are eight of them) vitamin B12 takes on a distinct role in cellular metabolism of carbohydrates, proteins and lipids (fats). It also aids in the normal function of the brain and nervous systems, affects the synthesis and regulation of DNA, and helps the body produce red blood cells. It is a very busy vitamin.

How much do I need?

The National Institute of Health recommends that healthy adults consume 2.4 micrograms (mcg) of B12 every day. Pregnant and breast feeding women should increase their intake to 2.6 and 2.8 mcgs of B12 per day, respectively to make up for the nutrition they lose from growing and feeding an infant.

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Where do I find it?

You can find Vitamin B12 naturally in many animal products such as fish, beef, poultry, eggs and milk. It is not as common in plant-based foods, though it can be synthetically produced in pill form and added to some non-animal-based foods such as cereal.

But, if you’re looking for natural sources of B12--which are always better than supplements--look no further than these delicious foods:

Clams – Three ounces of cooked clams contain 1,402 mcg of B12. That translates to about 1,402 percent of the daily-recommended value of B12 for a healthy adult.

Beef Liver – While not the most common of entrees, 3 ounces of beef liver contain 70.7 mcg of B12. That is 1,178 percent of the daily-recommended value of B12.

Fortified breakfast cereals – We know that plant-based foods on their own are not rich in B12. But, many breakfast cereal manufacturers will add vitamin B12 to their cereals along with other nutrients. Most breakfast cereals that have been fortified will contain between 1.5 and 6 mcg of B12 per serving. But watch out for cereals that are also high in sugar.

Fish – Many varieties of fish contain a good amount of vitamin B12, such as:

  • Wild rainbow trout = 5.4 mcgs per 3-ounce serving
  • Cooked salmon = 4.8 mcgs per 3-ounce serving
  • Canned tuna = 2.5 mcgs per 3-ounce serving

Dairy – Many dairy products also are very good sources of vitamin B12:

  • Low-fat Milk = 1.2 mcg per one cup
  • Low-fat Yogurt = 1.1 mcg per eight ounces
  • Swiss Cheese = 0.9 mcg per one ounce

Eggs – A whole, hard-boiled egg has 0.6 mcg of vitamin B12 or about 10 percent of the daily-recommended value of B 12.

Chicken – Three ounces of chicken will give you 0.3mcg of Vitamin B12.

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Just think

If you eat beef liver and clams tonight you’ll be able to hit your B12 intake for the day 10 times over.

B12 Deficiencies

The body is able to store several years’ worth of vitamin B12 in the liver so deficiencies for most people are very rare. But, if beef liver isn’t your thing (nor any of the other foods on the B12 list), you may end up with a vitamin B12 deficiency.

Vegetarians are at an increased risk for vitamin B12 deficiencies because they generally do not eat foods rich in B12. Women who are vegetarians while pregnant and breast-feeding are especially at risk for vitamin B12 deficiency, as well as their babies.

Some people become vitamin B12 deficient due to other health conditions. For example, people who suffer from Crohn’s disease or ulcerative colitis are often unable to adequately absorb any nutrients from the foods they eat. As a result, they become deficient in many essential vitamins and minerals.

Vitamin B12 deficiency is often treated with injections. This allows the vitamin to be introduced directly into the bloodstream and bypass potential barriers to absorption caused by other medical problems.


National Institutes of Health, Dietary Supplement Fact Sheet: B12. (June 2011). Retrieved from:

Mayo Clinic, Vitamin B12 (2012). Retrieved from: