Vitamin B-12 is a water-soluble B vitamin available naturally in many animal-based foods and in supplement form, according to MedlinePlus. The vitamin supports metabolism, aids in red blood cell formation, and supports the central nervous system.
Vitamin B-12 occurs naturally in meat, shellfish, eggs, dairy products and poultry as well as in some cereals, notes MedlinePlus. Plant foods only have vitamin B-12 if they are fortified with the vitamin. Animal-based foods allow the body to absorb the vitamin and provide the most reliable source.
Possible effects of low vitamin B-12 levels in the body include anemia, balance issues, weakness and tingling or numbness in extremities, states MedlinePlus. People who are over 50, eat a vegetarian or vegan diet, or have had gastrointestinal surgery and those with digestive disorders may have a vitamin B-12 deficiency due to difficulty absorbing the vitamin.