Why is vitamin B12 important for the nervous system?

B12's nerve job is maintenance: it keeps myelin — the insulation nerves signal through — intact. When B12 runs low, the insulation frays from the longest nerves inward, which is why the feet feel it first: tingling, numbness, then balance. The two features that make this deficiency clinically urgent: nerve damage has a clock on it, and the body stores years of B12 — meaning the plant-based eater who stopped absorbing it a decade ago is only now getting the bill. This guided journey covers the insulation, the map, and the urgency.