The Importance and Best Sources of Vitamin B12 What is Vitamin B12 (Cobalamin)? Vitamin B12 is also known as (Cobalamin) which plays an important role in the RBC formation, cell metabolism, nerve function, and the production of DNA. Vitamin B12 is one of the eight B vitamins. Vitamin B12 is easily soluble in water Vitamin B12 is an essential nutrient