The B12 Issue

When you transition to a vegan diet, non-vegans will always question where you're going to get your protein and calcium.  Those who are slightly more informed about nutrition will often caution you that you will become vitamin B-12 deficient, since the best sources of vitamin B-12 are liver, milk, and fish.

Well, there may be a real reason to be concerned, at least with regard to B-12.  Data from a small study at Oxford shows that people with lower levels of B-12 in their blood suffered from brain shrinkage six times more often than those with high levels of B-12. (Note: none of the 107 people in the study were actually B-12 deficient.)  Okay, so your brain is a little smaller, since we only use around 10% of our brains anyway, this shouldn't be a big deal, right?  Apparently not.  Shrinkage is usually associated with the development of dementia.  That's scary!  Since vegetarians, and vegans especially, don't consume liver, milk, or fish, we're at an increased risk of suffering from brain shrinkage.  See BBC News Health, and the University of Oxford's press release on B-12.

Why else is vitamin B-12 important?

In the body, B-12 helps the bone marrow regenerate red blood cells and has been credited with protection against heart disease and mental deterioration. Adequate B-12 in the diet is necessary to keep down levels of homocysteine in the blood. Homocysteine is a toxic amino acid produced in the breakdown of animal protein and has been identified as a risk factor for arterial disease and heart attack.

In children, B-12 deficiency can cause severe abnormalities of growth and mental retardation. In adults it causes pernicious anemia, a dangerous condition marked by weakness, apathy, lightheadedness, shortness of breath, fatigue, numbness in the arms and legs, loss of balance, and mental changes, all reversible if B-12 is supplied. Untreated, the symptoms can become permanent.

Source:  Dr. - Vitamin B-12 Shots

So how do we, as vegans, ensure that we get adequate vitamin B-12?  There's B-12 in nutritional yeast (make sure to read the label), fortified soy milk, fortified cereals, and vitamins.

Fermented soya products, seaweeds and algae have all been proposed as possible sources of B12. However, analysis of fermented soya products, including tempeh, miso, shoyu and tamari, found no significant B12.

Spirulina, an algae available as a dietary supplement in tablet form, and nori, a seaweed, have both appeared to contain significant amounts of B12 after analysis. However, it is thought that this is due to the presence of compounds structurally similar to B12, known as B12 analogues. These cannot be utilised to satisfy dietary needs. Assay methods used to detect B12 are unable to differentiate between B12 and it's analogues, Analysis of possible B12 sources may give false positive results due to the presence of these analogues.

Researchers have suggested that supposed B12 supplements such as spirulina may in fact increase the risk of B12 deficiency disease, as the B12 analogues can compete with B12 and inhibit metabolism.

The current nutritional consensus is that no plant foods can be relied on as a safe source of vitamin B12.

Source:  The Vegetarian Society

So it looks like we have to ensure that we supplement our diets with B-12.  Here are two slightly different recommendations on supplementation:

Vitamin B12: Although this is found naturally only in foods from animal sources, you can get sufficient amounts from fortified breakfast cereals, fortified soy beverages and some types of brewer's yeast. Still, I recommend taking a supplement of 50-100 micrograms of B12 in the form of a good multivitamin, sublingual tablet, nasal spray or gel.

Source:  Dr. on Becoming Vegan

Vegans who choose to use a vitamin B12 supplement, either as a single supplement or in a multivitamin should use supplements regularly. Even though a supplement may contain many times the recommended level of vitamin B12, when vitamin B12 intake is high, not as much appears to be absorbed. This means in order to meet your needs, you should take a daily vitamin B12 supplement of 5-10 micrograms or a weekly vitamin B12 supplement of 2000 micrograms (4).

Source:  Vegetarian Resource Group

Note: there is no tolerable upper intake level for vitamin B-12 because of its low toxicity.  There have been no toxic or adverse effects associated with large intakes of vitamin B-12 from food or supplements in healthy people.

Anyway, this is definitely something to take seriously.  We'll be keeping our eyes open for additional research on vegan/vegetarian B-12 issues.  In the meantime here are some links to help keep you informed on sources of B-12 in the vegan diet.


  1. Actually, some seaweeds do contain vitamin B12 in forms that are absorbed by humans, even though it was originally thought they do not. The Vegetarian Society presents outdated information. However, most of us don’t eat enough seaweed to fulfill our B12 requirements. I suspect that you could get iodine poisoning from that. Still, it is false to claim there are no natural vegetarian sources of B12, as many sources mistakenly do.

    Some people do not absorb B12 well, and even a large percentage of people who eat dairy and meat regularly are deficient in B12.

    FWIW, as an interesting anecdote the illness I have (CFS/ME) is often treated with large dose vitamin B12 in injections or orally. 1 mg sublingual tablets helped me a great deal in the beginning, even though blood tests had showed I was far from deficient (I take a daily multivitamin with 3 mcg), but then stopped working. However, many people I know have had the same experience (even some healthy ones, and most of them omnivores), that B12 initially acts as an energy booster and then stops working. But injections could still help. Some people with CFS/ME have daily injections of up to 20 mg of B12… that’s about 7,000-20,000 times the RDA depending on where you live (and perhaps your age)!

    IMO all vegans should take supplemental B12 – and all omnivores should all have their blood levels tested, because they have about 1/4 chances of being deficient. But taking supplemental vitamin D (2,000-4,000 IU in the winter, less in the summer) is even more important, and goes for vegs and omnivores alike.

  2. just take a supplement. one a day. put it somewhere you will remember to take it – mine is next to the coffee.

    don’t worry so much. veganism isn’t hard, it just takes a little common sense.

  3. “Since vegetarians, and vegans especially, don’t consume liver, milk, or fish, we’re at an increased risk of suffering from brain shrinkage. ”

    Based on Oxford’s study that was done on elderly people only, I don’t think this is safe to conclude. The study did say the people weren’t even Vitamin B-12 deficient, they had low levels of B-12. And vegetarians and vegans certainly aren’t the only population at risk for lower levels of B-12.

    You do raise a good point though that vegans, just as anyone who is concerned about their health, should think about nutrition.

    People who eat meat should be very concerned about the effects of eating mercury-tainted fish and hormone-filled milk as well. And the fact that most animal foods are not given adequate food safety oversight, the thought of food borne illness should get many people to consider vegetarianism/veganism.

  4. According to T. Colin Campbell, author of The China Study, people are capable of storing a three-year supply of vitamin B12 in their bodies. The implication is that you don’t need a daily supplement, just a small dose “on occasion”. He also maintains that B12 comes from microorganisms that are found in healthy (organic) soil, and that foods grown in healthy soil will absorb it.

  5. My question is .. how do the animals get the B12 in the first place. I had understood that they don’t naturally produce it, but store it from something they ingest. Can’t we just eat what they eat to get B12?

  6. Caela, this is from wikipedia:

    “Vitamin B-12 cannot be made by plants or animals[5] as only bacteria have the enzymes required for its synthesis. The total synthesis of B-12 was reported by Robert Burns Woodward[6] and Albert Eschenmoser,[7][8] and remains one of the classic feats of organic synthesis.

    Species from the following genera are known to synthesize B-12: Aerobacter, Agrobacterium, Alcaligenes, Azotobacter, Bacillus, Clostridium, Corynebacterium, Flavobacterium, Micromonospora, Mycobacterium, Nocardia, Propionibacterium, Protaminobacter, Proteus, Pseudomonas, Rhizobium, Salmonella, Serratia, Streptomyces, Streptococcus and Xanthomonas. Industrial production of B-12 is through fermentation of selected microorganisms.[9] The species most often used, Pseudomonas denitrificans and Propionibacterium shermanii, are frequently genetically engineered and grown under special conditions to enhance yield.”

    Animals and plants do NOT synthesize vitamin B12, it is the microorganisms that exist in healthy soil and also inside the digestive systems of healthy animals, including humans.

    The reason that we, as vegans, don’t get enough B12 in our diets is because of the reckless use of herbicides and pesticides and other “scientific agricultural advances” which have killed all the soil we have to grow our food in.

    At least, this is my understanding.

  7. Hi Maija,
    Thanks for the information. Actually, I’d heard that from a friend too… that the B12 shots are helpful at first, but then the effect seems to wear off.

    Hi Becky,
    We’re not worried, but we do try to present a balance view of veganism, both the good and the bad.
    And we know plenty of people (omni and veggie) who don’t apply common sense to their eating. So this post will hopefully serve as a wakeup call to some people. 🙂

    Hi Anna,
    I don’t feel I’m in a position to recommend a particular supplement. Jane and I do take supplements, but we probably haven’t done enough research to recommend a brand. This is one of the reasons we suggest visiting a doctor or nutritionist… They’re better suited to suggest an appropriate supplement regemine. (Note: not all doctors are well versed in nutrition, and, as Gary notes, many doctors do not have adequate knowledge of vegan dietary issues.)

    Hi Daniela,
    Actually the study was done on people 61-87. 65 is the W.H.O. defined beginning of “elderly” so not all of the participants were elderly. Regardless, I hope to be elderly one day.
    Yes, omnivores should be concerned with what they’re consuming as well as vegans. I write about that on occasion. But this is a vegan blog and I think it’s important to point out things that may be of concern to vegans. If taking a simple supplement can help stave off alzheimers, I’m all for it, especially since there seem to be no ill effects to taking excess B12.

    Hi Doug,
    Peronally, I’d rather err on the side of caution and take a daily supplement, especially since there are no ill effects to taking excess B12.
    As for healthy organic soil, I’m not confident that all of my produce is grown in that manner.
    And, thanks for your answer to Caela!

    Hi Caela,
    Doug has answered the question about as well as I can… (I would have cited the same source.) It’s simple enough to get your hands on a B12 supplement – many mulitvitamins provide B12, and fortified cereals, etc.

  8. “When you transition to a vegan diet, non-vegans will always question where you’re going to get your protein and calcium. Those who are slightly more informed about nutrition will often caution you that you will become vitamin B-12 deficient, since the best sources of vitamin B-12 are liver, milk, and fish.”

    That’s right. Before i was a vegetarian and when i started to get depressed and weak, i asked my friend about my condition and she says that i was lack in vitamin b12 which i wasn’t aware of. i tried to search over the internet and i found this spray and as of now it’s pretty amazing, i ‘m back to normal.

  9. Hmm it looks like your site ate my first comment (it was extremely long) so I guess I’ll just sum it up what I submitted and say, I’m thoroughly enjoying your blog.
    I as well am an aspiring blog blogger but I’m still new to the whole thing. Do you have any tips and hints for rookie blog writers? I’d certainly appreciate it.

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