The story

The trail started with a disease that killed everyone who got it, which is why it was named pernicious anaemia. In the 1920s two Boston physicians found that feeding patients huge amounts of raw liver kept them alive, which meant the cure was a substance in the liver rather than anything the body could make. That substance was isolated in 1948 as vitamin B12, and Dorothy Hodgkin worked out its structure by X-ray crystallography in 1956, winning a Nobel Prize for it. Japan then took the molecule somewhere different: methylcobalamin became the standard nerve-repair form there, used for peripheral nerve problems and tested in motor neurone disease at very high amounts into muscle, and Japanese laboratories showed it driving Schwann cells to rebuild myelin after injury. That nerve-first view of B12 is largely an Asian contribution, and it is the one that matters most for root-cause work.