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We probably don't know any more people with the deficiency, because not everyone takes the test that determines B12 status. I just started taking it this year (I've had 10 years of not eating animals). But there are studies about it. Studies done by vegetarians and vegans.

There can also be a B12 deficiency in people who eat meat, especially those over 50-60 years old.

I follow you, I liked your Hive.

A hug.