Emily Johnson
Vitamin B12 is an essential nutrient that supports many important body functions, such as turning food into energy and maintaining nerve health. While most sources of B12 are animal-based, some mushrooms contain this vitamin, making them a good option for vegetarians and vegans. For example, shiitake mushrooms are known to have high levels of B12, and white button mushrooms also contain the vitamin.
| Characteristics | Values |
|---|---|
| Are mushrooms a source of vitamin B12? | Yes, some mushrooms contain vitamin B12. |
| Mushrooms with high vitamin B12 content | Shiitake, white button (Agaricus bisporus), and Oyster mushrooms. |
| Vitamin B12 content in dried Shiitake | 5.61 μg/50g to 100g |
| Vitamin B12 content in dried Oyster mushrooms | Traces of vitamin B12 |
| Vitamin B12 content in fresh Oyster mushrooms | High levels of vitamin B12 |
| Recommended daily vitamin B12 intake | 2.4 micrograms |
| What does vitamin B12 do? | Helps turn food into energy, produces and maintains the myelin surrounding nerve cells, and is important for mental ability, red blood cell formation, and the breakdown of fatty and amino acids. |
| What foods typically contain vitamin B12? | Animal products such as meat, fish, eggs, and dairy. |
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What You'll Learn
Shiitake mushrooms are a good source of B12
B12 is generally low across most varieties of mushrooms and is completely absent from plant sources. However, this is not the case for shiitake mushrooms, which are one of the few mushrooms with elevated B12 levels.
Shiitake mushrooms are cultivated and consumed throughout the world. Fresh and dried shiitake mushroom fruiting bodies are used in various vegetarian dishes. There are two types of high-grade dried shiitake fruiting bodies available in Japan: donko-type fruiting bodies with closed caps (early fruiting stage) and koushin-type fruiting bodies with open caps (late fruiting stage).
Shiitake mushrooms are thought to be able to access bacteria to make B12. A study found that dried shiitake fruiting bodies rarely contained an unnatural vitamin B12 [c-lactone] that is inactive in humans. Given that shiitake mushrooms lack the ability to synthesize vitamin B12 de novo, the vitamin B12 found in dried shiitake fruiting bodies is derived from bed logs.
The recommended daily amount of B-12 for adults is 2.4 micrograms. A 50-gram serving of dried shiitake mushrooms meets this daily requirement, with an average of approximately 5.61 μg of B12. B12 is important as it helps to convert glucose into energy and plays a role in nerve function. It is also essential in myelination, a process in which glial cells construct a membraneous sheath or insulation surrounding the axons of the neurons, optimizing the function of the central nervous system.
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B12 is generally low across most mushroom varieties
B12 is an essential B vitamin that our bodies need every day. It helps turn the food we eat into usable energy and supports many important body functions. The most common sources of B12 are animal products, such as meat, fish, eggs, and dairy, with a few plant-based sources available as well.
While mushrooms are often touted as a good source of vitamins, B12 is generally low across most mushroom varieties. Plant foods are not a natural source of B12 unless they are fortified, as B12 is made in the gut of animals. Mushrooms, therefore, are not a reliable source of B12 for vegans or vegetarians who do not consume animal products. However, there is one notable exception: the shiitake mushroom.
Shiitake mushrooms are one of the few mushrooms with elevated levels of B12. A serving of 50 grams of dried shiitake mushrooms will meet the daily recommended value of B12. The vitamin B12 found in shiitake mushrooms is derived from the bed logs on which they grow. This discovery is particularly important for vegetarians and vegans, as it provides a plant-based source of B12 to help prevent a deficiency.
In addition to shiitake mushrooms, cultivated white button mushrooms (Agaricus bisporus) have also been found to contain vitamin B12. Analysis of freshly harvested white button mushrooms from five farms showed that higher concentrations of vitamin B12 were detected in the outer peel than in the cap, stalk, or flesh, suggesting that the vitamin B12 is likely bacteria-derived. High concentrations of vitamin B12 were also found in flush mushrooms, including cups and flats.
While B12 is generally low in most mushroom varieties, the presence of this essential vitamin in shiitake and white button mushrooms provides valuable plant-based sources for individuals following a vegan or vegetarian diet.
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B12 is synthesised by certain bacteria
Vitamin B12, also known as cobalamin, is an essential vitamin with a wide range of functions in the human body. It is involved in metabolism, DNA synthesis, cell division, fatty acid and amino acid metabolism, and the maturation of red blood cells. B12 is naturally found in animal products like meat, shellfish, liver, fish, poultry, eggs, and dairy products. It is also added to breakfast cereals and is available in dietary supplements.
B12 is unique in that it is not produced by plants or animals; instead, it is synthesised exclusively by certain bacteria and archaea through microbial fermentation. In humans and other animals, B12 is synthesised by bacteria in the gut microbiota, specifically in the colon. However, it was previously believed that humans could not absorb B12 from the colon because it is located downstream from the small intestine, the site of nutrient absorption.
Recent studies have challenged this belief by demonstrating B12 synthesis in the small intestine, which is a major site of nutrient absorption. Specifically, bacteria in the small bowel, such as Pseudomonas and Klebsiella sp., have been found to synthesise significant amounts of B12. This discovery has important implications for understanding B12 absorption and addressing B12 deficiencies.
In addition to intestinal bacteria, certain foods like mushrooms have been found to contain B12. White button mushrooms (Agaricus bisporus) are a notable source, with higher concentrations of B12 detected in the outer peel than in the cap, stalk, or flesh. Shiitake mushrooms are also a rich source of B12, providing twice the daily recommended value in a 50g serving.
The presence of B12 in mushrooms is thought to be due to their ability to access bacteria for B12 synthesis. This makes mushrooms an excellent source of B12 for individuals following plant-based diets, as B12 is typically found in animal-derived foods. By incorporating mushrooms like shiitake and white button mushrooms into their diets, individuals can increase their B12 intake and promote overall health.
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B12 is an essential nutrient for many body functions
Vitamin B12, also known as cobalamin, is a water-soluble vitamin that is essential for many body functions. It is a key nutrient that our body needs but cannot produce, so it must be obtained from our diet or supplements. B12 plays a critical role in maintaining nerve health, supporting the production of DNA, and forming healthy red blood cells. It also helps to prevent birth defects, supports bone and eye health, and promotes healthy skin and hair.
B12 is naturally found in animal products, such as liver, beef, sardines, clams, and dairy. However, for those following a plant-based diet, B12 can be more challenging to access. It is made in the gut of animals, so plant foods are not a typical source of B12 unless they are fortified. This is where mushrooms come in.
Mushrooms, specifically shiitake, are one of the few plant-based sources of B12. Shiitake mushrooms have been found to contain good amounts of B12, with 50 grams of dried shiitake meeting the daily recommended value. This is especially beneficial for vegans and vegetarians who may struggle to get enough B12 in their diets. Other varieties of mushrooms, such as oyster mushrooms, are also a nutritional powerhouse, offering many health benefits, even if they do not contain high levels of B12.
Overall, B12 is an essential nutrient that supports various bodily functions. While it is typically found in animal products, mushrooms like shiitake provide a valuable plant-based source of this vitamin, making it more accessible to those on plant-based diets.
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B12 is made and stored in the gut of animals
B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is synthesized exclusively by certain bacteria and archaea. B12 is produced in the gut microbiota of humans and other animals. However, humans cannot absorb B12 from the colon, as it is produced downstream from the small intestine, where most nutrient absorption occurs. This is why B12 is typically obtained from animal products such as meat, liver, eggs, and milk.
B12 is made in the gut of animals by bacteria. Ruminants, such as cows and sheep, are foregut fermenters, meaning that plant food undergoes microbial fermentation in the rumen before entering the true stomach. This process allows them to absorb B12 produced by bacteria. Other mammalian species, such as rabbits and guinea pigs, consume high-fiber plants that undergo bacterial fermentation in the cecum and large intestine. The material from the cecum is expelled and re-ingested, allowing for B12 absorption.
B12 is stored in the liver and muscles of animals. It is also passed into their eggs and milk, making these animal products a source of B12 for humans. Meat, liver, eggs, and milk are therefore sources of B12 for other animals and humans. The bioavailability of B12 from eggs is less than 9%, while fish, fowl, and meat provide 40% to 60% bioavailability.
B12 is challenging to obtain from a plant-based diet because it is typically made and stored in the gut of animals. However, some plant and mushroom species can contain B12 through microbial interaction with bacteria in the soil or their aerial surfaces. For example, the white button mushroom (Agaricus bisporus) contains vitamin B12, with higher concentrations found in the outer peel than in the cap, stalk, or flesh.
The total amount of vitamin B12 stored in the human body is about 2–5 mg, with around 50% stored in the liver. Approximately 0.1% is lost per day through secretions into the gut, and excess B12 is excreted in urine. Nutritional deficiency of B12 is rare in adults due to the efficient enterohepatic circulation of B12, which allows the liver to store 3 to 5 years' worth of the vitamin. However, B12 deficiency is prevalent worldwide, particularly among those with low or no intake of animal products, such as vegans and vegetarians.
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Frequently asked questions
Yes, B12 is found in mushrooms, particularly in shiitake and white button mushrooms.
The amount of B12 in shiitake mushrooms varies, but on average, 50g of dried shiitake provides the daily recommended amount of 2.4 micrograms.
Yes, B12 is found in many animal products, including meat, fish, eggs, and dairy. Liver and other organ meats are particularly nutrient-dense.
B12 is an essential nutrient that helps turn food into energy and supports nerve function. Deficiency can lead to neuropathy and megaloblastic anemia.
B12 is generally considered safe and non-toxic. However, excessive intake of similar vitamin B9 can mask a B12 deficiency, so it is best to consume both vitamins within the recommended amounts.
