Biologically Active Vitamin B12 Compounds in Foods for Preventing Deficiency among Vegetarians and Elderly Subjects

The usual dietary sources of vitamin B-12 are animal-source based foods, including meat, milk, eggs, fish, and shellfish, although a few plant-based foods such as certain types of dried lavers (non) and mushrooms contain substantial and considerable amounts of vitamin B-12, respectively. Unexpectedly, detailed characterization of vitamin B-12 compounds in foods reveals the presence of various corrinoids that are inactive in humans. The majority of edible blue-green algae (cyanobacteria) and certain edible shellfish predominately contain an inactive corrinoid known as pseudovitamin B-12. Various factors affect the bioactivity of vitamin B-12 in foods. For example, vitamin B-12 is partially degraded and loses its biological activity during cooking and storage of foods. The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B-12 from naturally occurring vitamin B-12 compounds, including its degradation products and inactive corrinoids that are present in daily meal foods. The objective of this review is to present up-to-date information on various factors that can affect the bioactivity of vitamin B-12 in foods. To prevent vitamin B-12 deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify plant-source foods that contain high levels of bioactive vitamin B-12 and, in conjunction, to prepare the use of crystalline vitamin B-12-fortified foods.