Nutrition Diet: What mushroom is high in B12?

October 5, 2025 •

3 min read

While animal products are the primary dietary source of vitamin B12, certain fungi, like dried shiitake mushrooms, offer a noteworthy plant-based option containing active and bioavailable B12. So, what mushroom is high in B12, and how reliable is it for meeting daily nutritional needs? Let's explore the science behind this fascinating dietary finding.

Quick Summary

An examination of vitamin B12 sources reveals that dried shiitake mushrooms and certain cultivated white button mushrooms contain elevated levels of this essential nutrient. The vitamin originates from bacteria in the growing medium, and content can vary based on cultivation and processing. Dried shiitake offers a significant amount, but consistency is not guaranteed, suggesting it is best viewed as a supplemental food rather than a primary source.

Key Points

Dried Shiitake Is a B12 Source: Dried shiitake mushrooms contain biologically active vitamin B12, a rare finding in plant-based foods.
Content Can Vary: The amount of B12 in mushrooms is inconsistent and depends on factors like cultivation method and processing, with sun-drying potentially increasing content.
Not a Primary B12 Source: Due to variability, mushrooms are not a reliable primary source of vitamin B12 for vegans or vegetarians, who should also rely on fortified foods or supplements.
Button Mushrooms Have Some B12: Cultivated white button mushrooms also contain modest amounts of bioavailable B12, concentrated more in the peel.
Bacterial Origin: The B12 found in mushrooms is not produced by the fungus itself but is acquired from bacteria present in its growing medium.
Combine Sources for Adequacy: For consistent B12 intake on a plant-based diet, a combination of fortified foods, supplements, and B12-containing mushrooms is recommended.

The Quest for Plant-Based Vitamin B12

Vitamin B12, or cobalamin, is a crucial nutrient for red blood cell formation, nerve function, and DNA synthesis. It is naturally found in animal products, posing a significant challenge for individuals on strict vegan or plant-based diets. While fortified foods and supplements are the most reliable sources, some research suggests certain mushrooms may offer a natural, if variable, alternative.

The Surprising Source: Dried Shiitake Mushrooms

Dried shiitake mushrooms (Lentinula edodes) are the most promising mushroom source of vitamin B12. Studies have shown that commercially available dried shiitake can contain high levels of biologically active vitamin B12. In fact, some research indicates that a 50-gram serving of dried shiitake could potentially meet an adult's daily B12 requirement of 2.4 micrograms, though the amount can vary widely. The vitamin in shiitake is believed to originate from bacteria present in the fungi's cultivation substrate, rather than being produced by the mushroom itself.

Cultivated White Button Mushrooms

Beyond shiitake, research has also identified the presence of active vitamin B12 in cultivated white button mushrooms (Agaricus bisporus). The B12 content in these mushrooms is also attributed to bacteria in their compost growing medium. Notably, the highest concentrations are found in the outer peel of the mushroom, though the overall amount is generally modest and varies significantly depending on the farm. While not as potent as dried shiitake, they represent another possible, though less significant, natural mushroom source of the vitamin.

Factors Influencing Mushroom B12 Content

The B12 content in mushrooms is not consistent and can be influenced by several factors, including:

Drying Method: Sun-drying has been shown to increase the vitamin B12 levels in mushrooms, likely due to UV exposure.
Cultivation Practices: Since the vitamin is derived from bacteria, the composition of the growing medium and the microbial interactions during cultivation play a major role in the final B12 concentration.
Mushroom Type: Different species and even varieties can have different abilities to accumulate vitamin B12. Oyster mushrooms, for instance, contain many B vitamins but notably lack B12.

Comparison of B12 Sources

To put mushroom B12 into perspective, here is a comparison with other common B12 sources:


Source	Form	Typical B12 Content (Approx.)	Reliability	Note
Dried Shiitake Mushroom	50g	Up to 5.61 μg/100g	Variable	Depends on cultivation and drying process
Cultivated White Button Mushroom	100g	1-2.5 μg/100g (varies)	Variable	Lower concentration than dried shiitake
Fortified Nutritional Yeast	15g (1/4 cup)	8.3–24 μg (per brand)	Reliable	An excellent and common vegan source
Fortified Plant-Based Milk	1 cup	0.6–2.07 μg	Reliable	Easy way to incorporate B12 daily
Nori Seaweed	4g	Can meet daily needs	Variable	Content depends on the species and conditions
Beef Liver	100g	60 μg	Reliable	Animal product, highest natural source

The Reliability Question and Dietary Considerations

While dried shiitake mushrooms are a viable plant-based source of vitamin B12, they should not be considered a consistently reliable primary source for those on a strict vegan diet. The wide variability in B12 content makes it difficult to guarantee a sufficient intake from mushrooms alone. A balanced approach for a vegan or vegetarian diet should involve consuming a variety of B12-rich foods, including fortified options, and potentially supplementing to avoid deficiency. However, adding dried shiitake to soups, stews, and other dishes is a delicious way to boost B12 intake as part of a varied and nutritious diet.

Conclusion: A Fungal Friend for B12

Dried shiitake mushrooms are an interesting and unique plant-based source of active vitamin B12, offering a potential contribution to a vegan or vegetarian diet. While cultivated white button mushrooms also contain some B12, dried shiitake provides a more significant amount. The origin of this vitamin in mushrooms is bacterial, and its concentration can vary, making it an unreliable sole source of B12. For consistent intake, fortified foods and supplements remain the most dependable choice. Nevertheless, incorporating dried shiitake into your meals is a great way to enjoy its rich flavor and nutritional benefits, including its modest B12 content.

Outbound Link

For more information on the health benefits of mushrooms and nutrition, check out this resource from the Australian Mushroom Growers association: Mushrooms for Health.

Frequently Asked Questions

Dried shiitake mushrooms contain elevated levels of biologically active vitamin B12. A 50-gram serving of dried shiitake can potentially meet the daily B12 needs of an adult.

No, not all mushrooms are high in B12. Many mushrooms contain only trace amounts or none at all. The highest levels are typically found in dried shiitake mushrooms and some cultivated white button mushrooms.

Mushrooms do not produce vitamin B12 themselves. The vitamin is synthesized by bacteria present in the growing medium (substrate) on which the mushrooms are cultivated, and the fungus absorbs it from there.

Yes, studies on dried shiitake and cultivated white button mushrooms confirm that they contain true, biologically active vitamin B12, not the inactive 'pseudo' form found in some other plant sources.

No, vegans should not rely solely on mushrooms for their B12. The vitamin content in mushrooms can be highly variable and is not consistently sufficient to meet daily requirements. Fortified foods and supplements are more reliable options.

While some sources suggest that sun-drying can increase the B12 content in mushrooms, research primarily highlights the benefits of sun exposure for increasing vitamin D levels, not necessarily B12. However, the B12 content is already higher in dried shiitake compared to fresh.

Other reliable vegan sources of B12 include fortified nutritional yeast, fortified plant-based milks (such as soy and almond), and fortified cereals. Many vegans also opt for B12 supplements for consistent intake.