The Four Stages of Vitamin B12 Deficiency

Given up animal foods? How to ensure you don’t get to stage four. The damage could be irreversible.

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If you recently switched to a 100% plant-based diet, you should be OK for quite a while. The adult liver can store enough vitamin B12 to last 1–5 years. But after that, and without “careful planning”, you could suffer serious and irreversible damage to the central nervous system.

You often hear and read that a plant-based diet can be a healthy one, with enough careful planning. Unfortunately, further details of what that entails are not always forthcoming. So, in the interests of ensuring a carefully planned, plant-based diet, I outline below the four stages of vitamin B12 deficiency — and how to make sure you don’t get to stage four.

Vitamin B12, also known as cobalamin because it contains the trace element cobalt, is not found in plant foods. It is made by bacteria in the guts of animals and migrates from gut to muscle. A water-soluble vitamin, B12 is crucial to the brain and nervous system, red blood cell formation and DNA.

The central nervous system is especially vulnerable to vitamin B12 deficiency.

Writing in the British Medical Journal in 2013, researchers describe the case of a 25-year-old man with…