B12 Analogue in Mushrooms
(Note that I use the term “analogue” to refer to both active and inactive vitamin B12 analogues.)
There is a rumor going ’round that mushrooms are a good source of vitamin B12.
In June, a paper was published looking at the B12 analogue content of mushrooms in Australia (1). The authors used chromatography and mass spectrometry to determine whether the B12 was an active form, and they believed that it was.
The table at this link shows the B12 analogue content of the batches of each mushroom containing the most B12 and the batches containing the least. Assuming that the B12 is active analogue (an assumption that has not been confirmed by testing to see if it lowers MMA levels), it would take anywhere from 7 to 326 cups of mushrooms to meet the RDA.
As for the source of the B12, the authors were not sure, but they said:
“The high concentration of vitamin B12 in peel suggests that it was not synthesized within the mushrooms but was either absorbed directly from the compost or synthesized by bacteria on the mushroom surface. The latter is more likely because mushrooms have no root system to take up the vitamin in the compost as is the case with the uptake of vitamins by root plants from the soil containing fertilizers.”
The take home message: As with anything that has fecal contamination, these mushrooms might be a source of tiny amounts of vitamin B12. For many reasons, vegans should not rely on mushrooms for their B12.
1. Koyyalamudi SR, Jeong SC, Cho KY, Pang G. Vitamin B12 is the active corrinoid produced in cultivated white button mushrooms (Agaricus bisporus). J Agric Food Chem. 2009 Jul 22;57(14):6327-33. PubMed PMID: 19552428.