B12 is an exceptional, unique vitamin. This vitamin is of vital importance for us because it is involved in the metabolism of every cell of the human body. It plays a key role in the normal functioning of our brain and nervous system, the red blood cells formation, DNA synthesis, fatty acid and amino acid metabolism.
No fungi, plants or animals (including humans) are capable of producing vitamin B12. Only bacteria and archaea have the enzymes needed for its synthesis. Animals must obtain vitamin B12 directly or indirectly from bacteria. Many herbivorous mammals absorb B12 produced by bacteria in their own digestive system: some, cows for example, must obtain B12 from bacteria in their rumens from bacterial fermentation of the food they eat before it moves to the intestine for absorption; others (like beavers) ferment in the large intestine and then consume these feces for absorption.
Daily value of vitamin B12
Daily value of vitamin B12 is 2.4mcg (micrograms) for average adults rising to 2.8mcg for lactating mothers. It is required in smaller amounts than any other known vitamin.
We can get vitamin B12 only from animal sources
Vitamin B12 is found in most animal-derived foods, including meat (especially liver), fish and shellfish, poultry, eggs, milk and milk products. However, the bioavailability from eggs is less than 9%, compared to 40% to 60% from fish, fowl and meat.
Industrial synthesis of vitamin B12
B12 is the largest and most structurally complicated vitamin and can be produced industrially only through a bacterial fermentation-synthesis. This synthetic B12 is used to fortify foods and sold as a dietary supplement.
Non-animal sources of vitamin B12
Although none of non-animal sources of vitamin B12 have been subjected to human trials, it is suggested that there is only one verified source of biologically active B12 – chlorella. Chlorella is a fresh-water single-cell green algae that acquire B12 through a symbiotic relationship with heterotrophic bacteria, in which the bacteria supply B12 in exchange for fixed carbon.
There are only two sources of vitamin B12 for vegans
The B12 vitamin is of note because it is not available from plant products, making B12 deficiency a legitimate concern for vegans. There are only two reliable sources of vitamin B12 for vegans capable of supporting optimal health: foods fortified with this nutrient (which includes nutritional yeast grown on a B12-rich medium) and supplements. It is of utmost importance that vegans ensure they have an adequate intake of B12. Any B12 supplement tablet should be chewed or allowed to dissolve in the mouth to enhance absorption.
Vitamin B12 is not toxic at high amounts because our bodies remove what is not needed.