An interesting read:
http://www.second-opinions.co.uk/vegetarian.html
[cough]vitamin B12[/cough]
"However, B12 deficiency is far more common than most health care practitioners and the general public realize. Data from the Tufts University Framingham Offspring Study suggest that 40 percent of people between the ages of 26 and 83 have plasma B12 levels in the low normal range – a range at which many experience neurological symptoms. 9 percent had outright deficiency, and 16 percent exhibited “near deficiency”. Most surprising to the researchers was the fact that low B12 levels were as common in younger people as they were in the elderly."
http://chriskresser.com/b12-deficiency-a-silent-epidemic-with-serious-consequences
Another reason foods are fortified.
"What Every Vegan Should Know About Vitamin B12
Very low B12 intakes can cause anaemia and nervous system damage.
The only reliable vegan sources of B12 are foods fortified with B12 (including some plant milks, some soy products and some breakfast cereals) and B12 supplements. Vitamin B12, whether in supplements, fortified foods, or animal products, comes from micro-organisms.
Most vegans consume enough B12 to avoid anaemia and nervous system damage, but many do not get enough to minimise potential risk of heart disease or pregnancy complications.
To get the full benefit of a vegan diet, vegans should do one of the following:
eat fortified foods two or three times a day to get at least three micrograms (μg or mcg) of B12 a day or
take one B12 supplement daily providing at least 10 micrograms or
take a weekly B12 supplement providing at least 2000 micrograms.
If relying on fortified foods check the labels carefully to make sure you are getting enough B12. For example, if a fortified plant milk contains 1 microgram of B12 per serving then consuming three servings a day will provide adequate vitamin B12. Others may find the use of B12 supplements more convenient and economical.
The less frequently you obtain B12 the more B12 you need to take, as B12 is best absorbed in small amounts. The recommendations above take full account of this. There is no harm in exceeding the recommended amounts or combining more than one option."
http://www.vegansociety.com/lifestyle/nutrition/b12.aspx[/QUOTE]
I have known vegans who actually have the honesty to admit they take B12 supplements.
(see my previous link):
Vitamin B-12 is unique among vitamins in that while it is found universally in foods of animal origin, where it is derived ultimately from bacteria, there is no active vitamin B-12 in anything which grows out of the ground. Where vitamin B-12 is found on plants it is there only fortuitously in bacterial contamination.
Bacteria in the human colon make prodigious amounts of vitamin B-12. Unfortunately, this is useless as it is not absorbed through the colon wall. Dr. Sheila Callender (14) tells of treating vegans who had severe vitamin B-12 deficiency by making water extracts of their stools which she fed to them, thus affecting a cure. An Iranian vegan sect unwittingly also makes use of the fact that human stools contain vitamin B-12. Investigators could not understand how members of this sect remained healthy until their investigations showed that they grew their vegetables in human manure — and then ate the vegetables without being too fussy about washing them first (15) .
To enable vegans to survive, vitamin B-12 is added artificially to breakfast cereals in Britain and may be bought in pill form. This is hardly a natural way to get food and in many cases it is self-defeating. Vitamin B-12 is also unlike all other vitamins in that it occurs as a number of analogues, only one of which, cyanocobalamin , is active for humans. In collecting human stools for analysis Dr. Victor Herbert found that of each one hundred micrograms of vitamin B-12 extracted, only five micrograms was of the cyanocobalamin analogue (16) . Thus even in this most prodigious source of the vitamin ninety-five percent was composed of analogues which were useless.
And:
In England a carefully conducted study (18) carried out on vegans showed that they all got vitamin B-12 deficiency eventually.
