Active B12 Found in Many Plant-Based Fermented Foods & Mushrooms

Vitamin B12 is an essential nutrient, especially important for red blood cell production and prevention of anemia. While B12 was previously thought to only originate from animal foods, emerging research reveals that certain plant foods may naturally contain significant levels of active B12 forms through symbiotic bacteria relationships. However, B12 levels in plants can vary greatly depending on factors like fermentation and bacteria strains.

Fermented Plant Foods as Possible Natural B12 Sources

Several fermented plant foods like tempeh, sauerkraut, kimchi, kombucha, and alkaline-fermented legumes may provide nutritionally relevant B12, but amounts depend on fermentation methods. Home fermentations using certain beneficial bacteria can yield higher B12 levels than commercial sterilized versions. For example, homemade sauerkraut averaged 2 mcg B12 per 100g versus negligible amounts in commercial sauerkraut.

Certain beans fermented with propionibacterium freudenreichii showed 7 mcg per 100g. A study on fermented locust beans, a traditional African food, astonishingly claimed 450 mcg per 100g. Palm wine also contained 20-30 mcg B12 per 100ml. Further human studies analyzing blood marker improvements are needed to substantiate these plant food B12 claims.

Mushrooms – Potentially Significant B12 Source

Mushrooms like shiitake contain no B12 analogues and may provide nutritionally relevant B12 levels around 2-6 mcg per 30g dried, though amounts are variable. A study found vegans consuming 7 mcg B12 daily from varied mushrooms maintained normal short-term blood markers, but follow-up beyond 8 months is needed. Consuming both mushrooms and the seaweed nori may be an unreliable long-term plant-based B12 strategy.

Nori Seaweed – B12 Bioavailability Depends Preparation

Nori reportedly contains up to 100 mcg B12 per 100g, but drying may convert B12 into inactive analogues. Dried nori lowered B12 status in one study, while another found raw nori maintained but did not improve B12 status in vegans after 8 months. Some data suggests nori’s B12 bioavailability depends on preparation method.

Other Plant Foods – Sporadic B12 Findings

Small amounts of B12 were found in couch grass and sunflower-family plants, while specific date varieties measured up to 2 mcg B12 per 100g. Further studies analyzing B12 blood markers are needed to confirm biological relevance.

B12 Analogs – Potential Issues and Speculation

Whileinactive B12 analogs may interfere with B12 absorption, early research suggests certain analogs may have B12-like functions in the body potentially reducing deficiency risks. However, analog bioequivalence to true B12 remains theoretical requiring extensive further study.


Some fermented plant foods and mushrooms may provide nutritionally meaningful B12 intake to reduce deficiency odds, but amounts are variable and human study data is very limited. Well-planned vegan diets should still prioritize B12 fortified foods and supplements to ensure adequate intake. Further clinical trials are needed measuring blood markers of subjects consuming potential plant B12 sources over long-term periods.