Vitamin B12, which can only be synthesized by bacteria, is present in animal products such as meat, poultry, fish (including shellfish), mussels, and to a lesser extent milk, but it is not generally present in plant products or yeast (1).
Fresh pasteurized milk is an important source of vitamin B12 for some vegetarians (27). Vegans need supplemental vitamin B12 to meet their requirements.
Also, individuals over the age of 50 should obtain their vitamin B12 in supplements or fortified foods such as cereal because of the increased likelihood of food-bound vitamin B12 malabsorption.
Cyanocobalamin is the principal form of vitamin B12 used in supplements but methylcobalamin is also available as a supplement. Over-the-counter preparations containing cyanocobalamin include multivitamin, vitamin B-complex, and vitamin B12 supplements (37).
Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.2017