[dietrichepp]

> vitamin B12 is not naturally found in yeast extract, but is added to Marmite during manufacture

Perhaps it would be more accurate to say that it can't be found in plants, but it can be found in animals and it can be produced industrially.

[dllthomas]

And for the record, "produced industrially" means farming bacteria, effectively (per Wikipedia) - it's not synthetic or derived from meat.