Cobalamin or vitamin B12 is the largest and most complex vitamin. A slight deficiency can cause anemia, fatigue, depression, mania and a long term deficiency can cause damage to the brain and central nervous system.
Here’s some videos about vitamin B12.
First, Dr. Graham, author of 80/10/10, speaks about vitamin b12 deficiency.
Here is Susan Yara and Anna Jiminez of New Beauty Magazine talking about their experience of getting B12 injections for a month.
Here is Dr. Elana Gelman, a naturopathic doctor, with information about B12.