B12 is the largest and most complex of all vitamin molecules. It cannot be synthesized. This vitamin is used by the body in such small quantities that the amount on the head of a pin would prevent deficiency for three years (1 milligram). B12 is so minute, it is measured in billionths of a gram.
B12 is formed through microbacterial action. This occurs in the ground by the bacteria in the soil, bacterial action in the stomachs of cows and pigs, and by bacterial action in the intestine of man.
Normally, B12 is absorbed by plants from the bacterial action in the ground. Sadly, soil bacteria have been destroyed through modern farming. Pesticides leach into the ground, killing the bacteria responsible for creating B12. If B12 is not in the soil, it’s not in your veggies.
What about B12 in the intestine? Meat, the recommended source of B12, ferments and creates toxic by-products which destroy intestinal bacteria. Non-B12-producing harmful bacteria take over. This leaves you totally dependent on the B12 derived from the bacterial action of cows and pigs.
There are very few non-meat sources of B12. Tofu, tempeh and soy sauce are made from fermenting soybeans. The fermentation makes these products a source of B12. However, taking a B complex vitamin supplement is a good insurance policy for vegetarians.