California Natural prefers the methylated form of Vitamin B12 called Methylcobalamin. The coenzyme form of B12 is the most active form of vitamin B12 in the body, especially the brain and nervous system. Most forms of B12 on the market are cyanocobalamin which is less expensive, but also less effective. Methylcobalamin is essential for cell growth and replication. The liver may not convert cyanocobalamin, the common supplement form of vitamin B12, into a adequate amounts of methylcobalamin which the body needs for proper nerve cell and other functioning.