I have had a very bad reaction to shiitakes when I've eaten them raw, cooked, and in capsule form I get really nauseated and then have bad, but quick, diahrrea. Anyone know what might be the cause of this? Is it an allergy? I don't get this reaction from white buttons, or portabellas.
Mushrooms cultivated on manure enriched compost will contain vitamin B12. If the mushrooms are not over washed before use they will contain some B12. There is 0.26ug of vitamin B12 in 100g of mushrooms. A serving of 4-6 mushrooms weighs 75g.
(Italized part, italized by me)
But they mention manure, while Shiitake grow on logs of wood.
So far I can't find anything to back the claim Dr.Kanichi makes.
I did find a few mentions that mushrooms contain a b12 analog / non-active b12.
Shiitake grow on wood naturaly, but it is possible to grow them in compost. The thing about fruiting fungi is that it doesn't care what it's grown on, only that it's enzymes can break it down and that it has the nutrients it needs.
B12 analogs/real B12 is a marketing thing, there is no such thing as pure B12 in anything found in nature. Not unless you can find a situation where every molecule a bacterium encounters is cobalt. That does not happen.
Fungi will absorb B12 directly regardless of the molecule it's based on.
Also shiitake is best cooked, as fungi can harbor salmonella and other pathogens. Also raw fungi fruit are not especially damaged by cooking like plants are, as they are mostly amino acids.
Lastly, shiitake are pretty easy to grow. Unless keeping a contant environment and spraying a mist of water on a mushroom patch is too hard, you can grow your own.