Vitamin B12 deficiency is written about in many medical textbooks and its causes and effects are well-established in the scientific literature.
Vitamin B12 deficiency is often missed for two reasons. First, it’s not routinely tested by most physicians. Second, the low end of the laboratory reference range is too low.
Vitamin B12 works together with folate in the synthesis of DNA and red blood cells. It’s also involved in the production of the myelin sheath around the nerves, and the conduction of nerve impulses.
B12 is the only vitamin that contains a trace element (cobalt), which is why it’s called cobalamin. Cobalamin is produced in the gut of animals.
It’s the only vitamin we can’t obtain from plants or sunlight. Plants don’t need B12 so they don’t store it.