Do Mushrooms Really Contain Vitamin B12?
The Truth Every Vegan Should Know
As a naturopath that puts a big focus on health through diet and nutrition, I often have clients come to me that are either on a vegan diet and not feeling right, or are considering moving to a plant-based diet and want to ensure they’re getting the right nutrients.
When you first embrace a plant-based lifestyle, vitamin B12 quickly becomes a hot topic. Before going vegan, you might not have given much thought to this essential nutrient, but soon discover that B12 plays a crucial role and if left unattended can result in permanent brain damage as well as in low mood, declining memory, and nervous system disorders. That’s why understanding B12 becomes so important when transitioning to a vegan diet.
I often see people suggesting that eating mushrooms will solve the B12 question. While there’s some truth to this idea, I believe most of it comes from clever marketing by mushroom growers. Let’s examine what the research actually tells us.
According to the Australian Food Standards, there are no plant-based foods that naturally contain vitamin B12. “But wait,” I hear you saying, “I thought mushrooms contained B12?” This confusion makes sense, and there’s a fascinating explanation behind it.
Vitamin B12 isn’t actually produced by plants or animals—it’s created by bacteria! Yes, those same tiny microorganisms living in your gut are responsible for making B12. For any food to contain B12, it must either have B12-producing bacteria present or have come into contact with them. Animal products contain B12 because of the bacteria living inside the animals that is being consumed.
When mushrooms contain B12, it’s not because the mushroom itself produces it, but because it has been exposed to B12-synthesizing bacteria in the soil. This means you’re consuming B12 from bacteria on the mushroom’s surface, not from the mushroom itself.
Not all mushrooms grow in environments with these specific bacteria. Research has identified several varieties that may contain B12: shiitake, porcini, black trumpet, golden chanterelle, and pleurotus. Unfortunately, these mushrooms are either hard to find, contain too little B12 to make a difference, or require you to eat impractically large amounts daily.
Let’s look at the numbers more closely. The recommended daily intake of vitamin B12 is 2.4 micrograms (μg) per day—that’s one millionth of a gram.
| Type of Mushroom | B12 Content | Problem |
| Shiitake Mushroom | 3.95-5.61 μg per 100g | Good source, but difficult to consume adequate amounts every day |
| Porcini or Pleurotus Mushroom | 0.01-0.09 μg per 100g | Not enough to reach recommended daily intake |
| Pleurotus mushroom species from Sicily | 0.44-1.93 μg per 100g | Good source, but research only on mushrooms found in Sicily |
| Black Trumpet/Golden Chanterelle | 1.09-2.65 μg per 100g | Not common mushrooms – difficult to source regularly |
Unless you’re prepared to eat 100 grams of shiitake mushrooms every single day (which would be quite a commitment!), you’ll want to look elsewhere for your B12 needs.
From my research, the most reliable sources of vitamin B12 in a vegan diet come from fortified foods such as certain soy milks, brewer’s yeast, some brands of nutritional yeast, yeast spreads like Vegemite, specific breakfast cereals, and some vegan meat alternatives. Keep in mind that the quality and fortification methods vary between brands, affecting how much B12 you actually receive.
If you’re not consistently including B12-fortified foods in your diet, I always recommend a sublingual B12 spray for optimal absorption. For personalised guidance on finding a quality B12 supplement or improving your plant-based nutrition, consider booking a consultation to ensure your vegan diet supports your optimal wellbeing – Tara.