h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

One thing that worries me (slightly) about B12 supplements. If B12 is only available from animal sources - what do they make the supplements out of?

Yes that bothered me to, I think genetically engineered bacteria, but i'm not sure...

I've just asked someone at the Vegan Society. I'll let you know if I get a reply. Their list of problems you'll get if you don't have enough B12 is enough to worry you into overdosing on supplements!

Ok, oddly enough the medical textbooks say that pernious aneamia is very rare in vegans.. I don't know if that's because everyone takes supplements, or because people slip up.

Isn't pernicious anaemia where your body starts breaking down the red blood cells itself? You'd have to be prone to the condition wouldn't you - vegan or not.

No that's heamolytic aneamia, pernious aneamia is when the body attacks the cells of the stomach that produce intrinsic factor, which is essential for adsorbing vitamin b12. So however much b12 you eat you can't adsorb it.

So you'd still have to have some predisposition towards getting it wouldn't you? Being vegan wouldn't automatically mean you should have it.

pernosis aneamia refers only to aneamia caused by b12 deficieny due to the body attacking the cells that enable b12 adsorbion. Vegans are no more likely to get this than anyone else!

But b12 deficiey due to not having enough of it in your diet is a different thing.. it's far less common, and mainly occurs in alcholics rather than vegans, as they get all their calories from alcohol.

Apparently some vegans with no identifiable source of B12 have been found to have none of the problems related to defficiency - it seems it's a big mystery as to how they survive! http://www.vegansociety.com/html/info/b12sheet.htm

I got a reply form the Vegan Society guy. They make the B12 for supplements from bacteria in a fermentation process. He said that the B12 from animal sources is ultimately from bacteria too. (Did you say that already?)

Don't think so because I didn't know it!

People who consume no animal products at all will, without some supplement, eventually have the very nasty sypmtoms of B12 deficiency that include dementia and death. In fact there is a case in New Zealand in which a child died and the parents were charged and found guilty of .... I think it was manslaughter as they had refused to give the child any animal products. For most people, however, eggs or dairy products will give sufficient B12. Also, the liver stores about 2 years' supply of B12 so the symptoms really do emerge over a fairly long period of time.

Interestingly, I am told that the B12 supposedly in mushrooms is an inefficient analogue of the useful B12 and actually makes things worse by replacing the useful B12 in the blood stream. Maybe the only useful B12 coming from a mushroom is if it is not washed properly.

For people with pernicious anaemia, dietary supplements are useless. Injections are necessary - the equivalent of about 200 beroccas straight into the arm can give quite a buzz.