A vegetarian hating friend sends me this article showing that vegetarians are more likely to have brain shrinkage than meat eaters.
That explains it, then.
More seriously, this article did not make me reach for a steak. It's perfectly easy to get enough B12 by using nutritional yeast, plus if you're me, eating non-vegan food that your relatives slip you on the grounds that what you don't know won't hurt you.
You should be using nutritional yeast anyway because it has a lovely, savory flavor. Particularly recommended in pesto to substitute for the parmesan cheese, and in your breakfast tofu scramble.
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