There are several forms of vitamin B12, all of which are termed "cobalamins" because they contain the trace mineral cobalt in their nucleus structure. Some forms of B12 are not immediately bioavailable and your body must use enzymes to convert them to a usable form. However, methylcobalamin and hydroxocobalamin (5-deoxyadenosylcobalamin) forms are highly bioavailable.
Where Can You Get Vitamin B12?
Your body doesn't make vitamin B12, you need to get it through your diet or by supplementation. It's found mostly in foods of animal origin such as meat, fish, and eggs. Even though only bacteria and archaea can synthesize B12, animals integrate B12 into their tissues via bacterial symbiosis, which is why animal foods are naturally the richest source of B12. Fortified foods and supplements are also common sources of the nutrient.
Why You Need Vitamin B12
Vitamin B12 plays an important role in a number of ways. The body functions that rely on adequate B12 include:
Brain and nervous system health via myelin sheath function
Red blood cell formation
Healthy cell metabolism (of nearly every cell in your body)
How Much Vitamin B12 Do You Need?