[fao_]

> Why does it seem bad? Less of something doesn't necessarily mean its bad.

Myelin is pretty damn important for the brain's function. Signals go much, MUCH slower without myelin, and there are a number of clinical disease and problems that can happen thereof. One of the main effects of B12 deficiency is loss of the myelin sheath around the optic nerve causing blindness, and the psychiatric effects of losing myelin in the brain -- in addition there are a lot of disorders where a primary effect is myelin degradation / loss. It's been very well studied.

[xeonmc]

Depleting your fridge is not the same as permanently destroying it.

[fao_]

B12 deficiency doesn't permanently destroy it either. It's just the body cannot produce myelin, and if that happens for a long enough period of time, the nervous system is exposed to damage that is permanent, even after the body can regenerate the myelin