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.
Vitamin B12 is found in:
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.
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:
The best way to meet your body's vitamin B12 needs is to eat a wide variety of animal products.
For people who do not eat animal products, vitamin B12 can be found in:
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 health care provider which amount is best for you.
Dietary Reference Intakes for vitamin B12:
Infants (adequate intake)
Adolescents and Adults
Escott-Stump S, ed. Nutrition and Diagnosis-Related Care. 6th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2008.
Sarubin Fragaakis A, Thomson C. The Health Professional's Guide to Popular Dietary Supplements. 3rd ed. Chicago, Il: American Dietetic Association; 2007.
Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. Washington, DC: National Academy Press; 1998.
Updated by: Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center Diabetes Care Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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