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 found naturally in a wide variety of animal proteins. Plant foods have no vitamin B12 unless they are fortified.

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 animal sources of vitamin B12 much better than plant sources. Non-animal sources of vitamin B12 vary in their amount of B12. They are not thought to be reliable sources of the vitamin.

Side Effects

A lack of vitamin B12 (B12 deficiency) occurs when the body does not get or is unable to absorb the amount of vitamin that the body needs.

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 breast-feeding 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: 1/7/2017
Reviewed By: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. 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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