Vitamin B12

Definition

Vitamin B12 is a water-soluble vitamin. Water-soluble vitamins dissolve in water. After the body uses these vitamins, leftover amounts leave the body through the urine.

The body can store vitamin B12 for years in the liver.

Function

Vitamin B12, like the other B vitamins, is important for protein metabolism. It helps in the formation of red blood cells and in the maintenance of the central nervous system.

Food Sources

Vitamin B12 is naturally found in animal foods such as fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods. Fortified breakfast cereals are a readily available source of vitamin B12. The vitamin is more available to the body from these cereals for vegetarians. Some nutritional yeast products also contain vitamin B12.

You can get the recommended amounts of vitamin B12 by eating a variety of the foods including:

To find out if vitamin B12 has been added to a food product, check the nutrition fact panel on the food label.

The body absorbs vitamin B12 from animal sources much better than plant sources. Non-animal sources of vitamin B12 have different amount of B12. They are not thought to be good sources of the vitamin.

Side Effects

Vitamin B12 deficiency occurs when the body does not get or is not able to absorb the amount of vitamin that the body needs.

Deficiency occurs in people who:

Talk to your health care provider about taking Vitamin B12 supplements.

Low levels of B12 can cause:

Recommendations

The best way to meet your body's vitamin B12 needs is to eat a wide variety of animal products.

Supplemental vitamin B12 can be found in the following:

The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should receive on a daily basis. The RDA for vitamins may be used as goals for each person.

How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and illnesses, are also important. Women who are pregnant or breastfeeding need higher amounts. Ask your provider which amount is best for you.

Dietary Reference Intakes for vitamin B12:

Infants (adequate intake)

Children

Adolescents and Adults


Review Date: 2/2/2019
Reviewed By: Emily Wax, RD, CNSC, University of Virginia Health System, Charlottesville, VA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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