Lower levels of B12 are associated with anemia and dementia. So most vegans, as well as those who follow calorie restriction diets, pay close attention to their B12 intake and often take a dietary supplement.
I was just enjoying a freshly made soup of crimini mushrooms and turnips, which go so well together. So I decided to find out more about criminis. I was surprised to find web sources claiming that crimini mushrooms are a vegan source of B12, containing one microgram of B12 per 100 grams. The RDA of B12 is 2.4 mcg/day. This would be a headline-making find, except for the fact that the form of B12 in mushrooms may not be biologically active in humans.
Furthermore, I cannot find a definitive study confirming this. Here is a little bit about B12 in other mushrooms. Pass the chanterelles, please.
J Nutr Sci Vitaminol
(Tokyo). 2012;58(6):438-41.
Watanabe F1, Schwarz J, Takenaka S, Miyamoto E, Ohishi N, Nelle E, Hochstrasser R, Yabuta Y.
Abstract
This study determined the vitamin B12 content of six wild edible mushrooms which are consumed by European vegetarians.
Zero or trace levels (0.01-0.09 µg/100 g dry weight) of vitamin B12 were determined in porcini mushrooms (Boletus spp.), parasol mushrooms (Macrolepiota procera), oyster mushrooms Pleurotus ostreatus), and black morels (Morchella conica).
By contrast, black trumpet (Craterellus cornucopioides) and golden chanterelle (Cantharellus cibarius) mushrooms contained considerable levels (1.09-2.65 µg/100 g dry weight) of vitamin B₁₂.
To determine whether C. cornucopioides or C. cibarius contained vitamin B₁₂ or other corrinoid compounds that are inactive in humans, we purified a corrinoid compound using an immunoaffinity column and identified it as vitamin B₁₂ based on LC/ESI-MS/MS chromatograms.
PMID: 23419403
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This study looked at B12 in other vegetables.
J Agric Food Chem. 2013 Jul 17;61(28):6769-75. doi: 10.1021/jf401545z. Epub 2013 Jul 2.
Watanabe F, Yabuta Y, Tanioka Y, Bito T.
Abstract
The usual dietary sources of vitamin B12 are animal-source based foods, including meat, milk, eggs, fish, and shellfish, although a few plant-based foods such as certain types of dried lavers (nori) and mushrooms contain substantial and considerable amounts of vitamin B12, respectively. Unexpectedly, detailed characterization of vitamin B12 compounds in foods reveals the presence of various corrinoids that are inactive in humans.
The majority of edible blue-green algae (cyanobacteria) and certain edible shellfish predominately contain an inactive corrinoid known as pseudovitamin B12. Various factors affect the bioactivity of vitamin B12 in foods. For example, vitamin B12 is partially degraded and loses its biological activity during cooking and storage of foods. The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B12 from naturally occurring vitamin B12 compounds, including its degradation products and inactive corrinoids that are present in daily meal foods.
The objective of this review is to present up-to-date information on various factors that can affect the bioactivity of vitamin B12 in foods. To prevent vitamin B12 deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify plant-source foods that contain high levels of bioactive vitamin B12 and, in conjunction, to prepare the use of crystalline vitamin B12-fortified foods.
PMID: 23782218
If you decide to use vegetarian sources for B12, I suggest testing B12 regularly to see if you are maintaining the level you wish.
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