One of the reasons why I didn't go through with the vegan diet at first was because I tried it for 3 days and felt so tired and unmotivated, drowsy and headached. I immediately thought I was lacking vitamin B12 (which we get from animal products).
But now I believe what I had was just a detox symptom, which is very common when one first goes on a vegan diet. All the animal toxins get released in your blood for elimination, but the process gets to you! A lot of people experience flu symptoms when they quit meat and dairy... it's expected!
So I have done some research on B12 and here's what I found:
Summary:
B12 is a bacteria containing cobalt, it is produced by the bile and the bacteria in our bodies (mouth, tonsils, intestine) also produce it, so you can easily get it from your own body! Not food! Moreover, more meat-eaters have B12 deficiency than vegans, and that's because the high-acidity of meat and dairy kills that bacteria! Lastly, the dietary requirements for B12 are based on a cooked food diet! If you're a raw vegan you may need a LOT LESS B12 than the average person who cooks almost all their meals.
Excerpts:
"Vitamin B12 is a microbe - a bacteria - it is produced by microorganisms. Vitamin B12 is the only vitamin that contains a trace element - cobalt - which gives this vitamin its chemical name - cobalamin - which is at the centre of its molecular structure. Humans and all vertebrates require cobalt, although it is assimilated only in the form of vitamin B12.
B12 synthesis is known to occur naturally in the human small intestine (in the ileum), which is the primary site of B12 absorption. As long as gut bacteria have cobalt and certain other nutrients, they produce vitamin B12. Dr Michael Klaper argues that vitamin B12 is present in the mouth as well and intestines. Furthermore, Dr Virginia Vetrano states that active Vitamin B12 coenzymes are found in bacteria in the mouth, around the teeth, in the nasopharynx, around the tonsils and in the tonsilar crypts, in the folds at the base of the tongue, and in the upper bronchial tree. [...]
Vitamin B12 is excreted in the bile and is effectively reabsorbed. This is known as enterohepatic circulation. The amount of B12 excreted in the bile can vary from 1 to 10ug (micrograms) a day. People on diets low in B12, including vegans and some vegetarians, may be obtaining more B12 from reabsorption than from dietary sources. [...]
External B12 coming into the body must be combined with a mucoprotein enzyme named Intrinsic Factor, which is normally present in gastric secretions, to be properly assimilated. If the Intrinsic Factor is impaired or absent, B12 synthesis will not take place, no matter how much is present in the diet. A B12 deficiency can be caused by antibiotics (from the drugs themselves and contained in milk and meat), alcohol (alcohol damages the liver, so drinkers need more B12) and smoking (and all high temp cooked food is smoky) and stress also raises B12 needs).
[It is believed] that a vitamin B12 deficiency is more widespread in vegans or vegetarians - this is probably just another marketing lie! In fact, many so-called studies 'showing vegans deficient' have to be carefully studied themselves - many of them do not prove vegans to be deficient at all! In fact, contrary to meat and dairy industry propaganda, meat-eaters are known to be more likely to have a vitamin B12 deficiency - this has been known since 1959! [...]
According to Marieb's 'Human Anatomy and Physiology', vitamin B12 can be destroyed by highly alkaline and highly acid conditions. This assumes that the B12 in meat would be easily destroyed because the hydrochloric acid in our stomachs during the digestion of meat is highly acidic. This may explain why meat-eaters are just as likely to have a B12 deficiency as vegans - even though their diet contains vitamin B12. Also, as mentioned earlier, another problem for meat-eaters is that there are normally antiobiotics in meat plus the fact that many meat-eaters destroy their friendly bacteria in their intestines by constant putrefaction and the putrefactive bacteria naturally present in meat will give the body a hard time. So, the damaged intestines may not function well enough to enable adequate vitamin B12 levels to be asborbed.
These minimum vitamin requirements may be inadequate to explain the needs of a healthy raw food vegan, for example, who may require less B12 due to an improved gastric ability and a high ability to recycle vitamin B12. (Cooking destroys microbes and a highly sterilised, cooked vegan diet may not provide the intestines with enough good quality flora). Absorption rates of B12 are inevitably higher in healthy individuals than in unhealthy individuals. Studies, based on healthy Indian vegetarian villagers, showed that none of them exhibited symptoms of B12 deficiency, despite levels of .3-.5 micrograms of B12."
Taken from: http://www.vibrancyuk.com/B12.html
