 How common is vitamin B12 deficiency among vegans? Last year a study was published in which B12 levels were measured in the blood of hundreds of British vegans. What percentage do you think were deficient? Less than a quarter? Almost a half? More than a half? Or were more than three-quarters of vegans testing vitamin B12 deficient? Now I'm not talking below average B12, or suboptimal B12 levels, or even what's clinically called B12 depletion, where your levels place you at high risk for deficiency, but actual bonafide vitamin deficiency, meaning that your levels are so low, your biochemistry is screwed up, your body just isn't working the way it should. And the answer is more than 50%, meaning you run into a vegan on the street, or at least on the street in London. Odds are they are suffering, whether they know it or not, from vitamin B12 deficiency. 52% deficient, 21% depleted. What about ovolacto vegetarians? 7 and 17%. One thing I hear from whiny vegans is that B12 deficiency isn't exclusive to vegetarians, meat-eaters can get it too, they're right, 0.4%. There's still enough in the general population for public health professionals to debate whether or not we should just mandate adding B12 to the grain supply, well then, though, what could explain this epidemic of vegan B12 deficiency? Easy, only a small fraction of British vegans were taking vitamin B12 supplements. Well, no wonder then. Hopefully vegans elsewhere are smarter. Everyone eating a plant-based diet must ensure a regular, reliable source of vitamin B12.