Doctor's Note

I make a similar "baggage" argument about meat in my video Food Is a Package Deal and about dairy in Plant vs. Cow Calcium. Tomorrow I'm going to get into the nitty-gritty on how much one needs on a weekly basis, and Wednesday's video-of-the-day will cover daily dosing. Or you can skip to Vitamin B12: How Much, How Often? and for background, see my blog post Vegan B12 Deficiency: Putting It into Perspective. For more on how many eggs would be required for other nutrients, see Egg Industry Blind Spot. And those with a thing for vegan bowel movement studies, see Bristol Stool Scale, Bowels of the Earth, Food Mass Transit, and Bowel Movement Frequency. And there are videos on a thousand or so other topics so please feel free to dig in!

For more context, check out my associated blog posts: How to Enhance Mineral Absorption, Preventing and Treating Kidney Failure With DietStool Size and Breast Cancer Risk, and  What Is the Healthiest Meat?

  • Michael Greger M.D.

    I make a similar “baggage” argument about meat in my video Food Is a Package Deal and about dairy in Plant vs. Cow Calcium. Tomorrow I’m going to get into the nitty-gritty on how much one needs on a weekly basis, and Wednesday’s video-of-the-day will cover daily dosing. Or you can skip to Vitamin B12: How Much, How Often? and for background, see my blog post Vegan B12 Deficiency: Putting It into Perspective. For more on how many eggs would be required for other nutrients, see Egg Industry Blind Spot. And those with a thing for vegan bowel movement studies, see Bristol Stool Scale, Bowels of the Earth, Food Mass Transit, and Bowel Movement Frequency. And there are videos on a thousand or so other topics so please feel free to dig in!

  • MacSmiley

    Please make this and ALL videos available on your YouTube homepage!!

  • Thea

    It may be a character flaw, but I have to say that I will never be that hard core.

  • BPCveg

    Is there any risk of toxicity associated with high intakes of vitamin B12?

    • Toxins

      No, it is water soluble so it easily exits our system. Similarly, vitamin c is water soluble. You can take way over the recommendations and be perfectly fine.

      • elsie blanche

        What is the long-term data on this, and how are we to know that the immune system is not somehow being “freaked out” by this immediate intake of such large amounts of B12, even prior to ingestion? I’ve had horrible reactions to B12 supplements at times (have experiment with all the different forms, amounts, and methods of intake) and I know others who have had horrific experiences with B12 supplements as well. Some to the point of near heart-attack symptoms. I and others would like to make the B12 thing work great, but the reality is is that for some it makes things far worse. (A theory of mine is that some people with SIBO or borderline SIBO issues end up “feeding” their SIBO bacteria to be even “stronger”. But I do believe there are many other factors at play in causing some people to dread ever having to take B12 in supplement form, after experience the scary reactions.

        • Seth Grimmr

          Are you sure you friends and yourself aren’t just finding yourselves caught in a web of hypochondria? If not, did you consider a smaller dosage? You do not have to eat a 2500 mcg supplement. You can take a daily supplement. Also, how often did you take it and what mcg level was it? These are all very important factors to your anecdote. I have actually heard of someone who broke out after beginning to supplement with B12. The breakouts stopped as soon as she quit taking them as frequently. One last thing, have you been checked for a potential allergy to anything in the supplements aside from the B12 itself?

          • elsie blanche

            Seth, thank you for inquiring and your words. I’ve checked all bases, it seems. And bloodwork has
            been done as well. Frustrating. I treat this like science, to the best of my ability. I’m in no way the only
            one out there who can not tolerate B12 supplements in any way shape or form. It is what it is for now.
            But if you come across a legitimate source of completely natural vegan B12 (not man made/lab factory
            produced) , please let me know.

  • Mark Biddy

    What if we were to fast for 24 hours every other day, I wonder of the body would be forced to absorb it’s homegrown B12.

    • Toxins

      We do in fact produce b12, but it is too low in our intestines to be absorbed. Our stools do contain b12 though.

  • tduke

    Dr. Greger what is your official recommendation for B12? how much, how often and what kind?

    Thank you!

  • nsd

    I’m sure this question has been asked before, but it sounds like you can’t be healthy vegan without taking supplements. Is this really a healthy diet then? Shouldn’t we as humans be able to thrive on whole foods alone? I really enjoy your educational videos, Dr. Greger, but I struggle with the idea that we are designed to use supplements. I would love to hear your thoughts on this topic. Thanks!

    • Toxins

      Vitamin B12 is a byproduct of bacteria, it was once found in our water supply, and on the plant foods we eat. Because we now chlorinate our water (to avoid getting sick from other bugs) and because we dont ground pick our vegetables from the wild without washing them, the only available source is now from animal products. This is of course an unnatural setting. Similarly, iodine is no longer found in plant foods. This is why the government iodized salt, to help Americans get adequate iodine intake. Similarly still, we do not expose ourselves to adequate sunlight, and the UV rays of today are much more potent then they once were in our evolutionary past so vitamin D must be supplemented for optimal health.

      Humans have changed their environment, so sometimes supplements are necessary to achieve optimal health.

      • Thea

        Toxins: For some reason, I didn’t see your reply on screen and it didn’t come to my e-mail account until hours after I had written my reply. Your reply is so good, I would not have bothered if I had seen yours first.

        • Toxins

          Thanks for the compliment and no problem, your reply below is pretty good too!

    • Thea

      nsd: This is a good question and one that gets asked often. Dr. Greger may have an answer for you, but I wanted to share my thoughts too.

      I’m aware of two main supplements which Dr. Greger recommends, and they both make sense. Vitamin D is recommended for everyone, whether vegan or not, because we are no longer running around naked at the equator. It doesn’t really have that much to do with your diet.

      Vitamin B12 is needed because our modern society has artificially cleaned up bacteria in water and soil. The cleaning up of the bacteria is generally a good thing since we then avoid the bad bacteria. The problem is that with steralized water and soil, we then loose the good by-product of some bacteria, i.e.: B12. So, where do you get your B12? Well, you could get it from animal products, but that is frought with danger since whole foods are package deals. (See the multitue of videos on this site about the likely cancer and other disease promoting properties of animal products.) Or you can get your B12 from a safe and inexpensive supplement.

      Modern humans no longer live in our native habitat – the environment that we evolved in. Thus it makes perfect sense that finding the healthiest way to live would require adjustments.

      I strongly encourage you to check out the following links from this site. The video shows typical vitamin deficiences (that we know about) in average vegans vs omnivores. I think this is the perfect answer to your question. What is the easiest way to eat healthy? Whole plant foods – supplemented when needed to accommodate our unnatural modern life.
      also check out this blog post where I think that Dr. Greger has at least partially answered your question more directly:

    • Freya Lynn Reed

      I’ve never had B12 issues, even though I’ve always had a low dietary B12 intake, even when I was a lacto-ovo. I do eat fortified cereals every once in a while, though. About 95% of my food is organic and wild.

      Here’s my post about B12!

      Many of us will never get B12 deficiency. Most of those that get B12 deficiency have absorption problems, which can be caused by many factors, including wrong diets, conditions like pernicious anemia, damaged gut, antibiotics and meds, etc.

      A human that lives a healthy lifestyle and eats a normal diet, does not get B12 deficincy. But most people live in an unnatural environment and eat wrong diets that are high in protein and fat, so it shouldn’t be surprising that they are at high risk of getting deficiencies.

      • beccadoggie10

        I’ve read from research gathered by Jeffrey Smith that Vitamin B-12 is now genetically engineered (recombinant DNA). And, I’ve noticed with most vitamins, that B-12, along with Vitamins C and E no longer work as supplements. So, I look for food sources, like sunflower seeds for vitamin E, a variety of raw fruits and veggies for vitamin C, and miso (not heated to high temperatures in cooking) for vitamin B-12.

        I do not want to eat GMO’s in fortified breakfast cereals, especially those where the owners of the companies have funded the Right to NOT know about GMO’s in Foods (and pharmaceuticals).

    • You can’t be serious

      Yeah let’s ignore all the diseases that people suffer from as a direct result of consuming animal products (people who consume animal products take supplements, too by the way) and declare that eating according to the way our bodies were designed must not be healthy simply because we gotta take one tiny pill a day because WE ruined our environment that used to provide us with B-12 by natural means. Good one!

  • Meha

    A Brazilian Portuguese version:

    • Michael Greger M.D.


  • ElaineV

    Love the “those are some hardcore vegans” comment :D

  • Michel Voss

    CV Dr. Sheila Callender, MD, D.Sc, FRCP

  • Jean Leduc

    A friend recently told me that the B12 I was taking as a supplement for vegan was a poor choice. I take tablet of cyanocobalamin with a meal and daily fortified soy milk and cereals. According to my friend, the superior way of getting B12 is with sublingual tablets. A quick research on the Net gave me 4 ways to get B12: injections, nasal spray, sublingual and swallowable tablets. All the sites claim to have the best product without citing any verifiable studies. AND they all happen to sell it… Is there a comparative study on the topic.

    • CloudTiger

      Forget studies. The cyanocobalamin is the WORST B12 to take.. it is not “natural” and is actually antagonistic to good B12, hydro or methyl. I would bin it and do my research before I bought next time. The consensus of those not selling out (to cheap cyanocobalamin and high profits) is methyl is best. Sublingual seems nicer than hypo injections but if I was seriously deficient I would not mess about. Straight to the net to buy methlyl jabs in high doses.

  • wchiwink

    being a vegetarian, (still eat sardines, mackerel, anchovies) i have been concerned with getting enough B12 – eat Marmite every morning, which is supplemented with it 0.6 % RDA for 4 grams…which brands for B12 supp. are best ?

    • Toxins

      Here are Dr. Greger’s recommendations for b12

      as well as the video series on b12

      I would also strongly advise you to cut out all fish consumption because fish is the most polluted animal product one can consume. Although true that the fish you are eating are lower in contaminants then most others, you are sitll exposing your body to envoronmental toxins that will build up over time and can cause neurological and hormonal problems.

  • WholeFoodChomper

    The image of the cow with the bacteria graphic that comes flying out of the cow’s nether regions has me laughing every time.  Love it!

  • Kathimecs

    Are there 2 types of B12? I have heard that the one type is not readily absorbed but the methylcobalamin is in a form that is readily absorbed. Is this true? Most of the the OTC suppliments contain the other form of the cobalamin. Is it worth taking these?

  • Alfred

    Is the below comment true?

    “This argument is still hanging around, however, according to Dr Vetrano it was disproved by research over 20 years ago and is nothing more than an obsolete scientific theory.  Indeed, in a 1999 version of ‘Human Anatomy and Physiology’ by Marieb, it states quite clearly that we do indeed absorb vitamin B12 through our intestines.” (

    • Dan

      Vetrano also claims that smallpox isn’t contagious. Stay away from the psudo- science quacks. B12 deficiency isn’t something to take a gamble on.

  • Wchiwink

    Yes, i too would like to know what type of B12 supp. to take….i just bought a “cyanocobalamine” one…is this good?
    (i did just end up in the hospital for a huge acute allergic reaction to something i ate or did recently….!)

  • Mel

    Hi, Im surprised no one mentioned nutritional yeast here?  I LOVE that stuff I use it most days in soups, on pasta etc.  As far as I am aware it is the only naturally occurring b12 food source that is also bio-available ( I believe that Dulce also contains b12 but it isnt bio-available due to chelation?)  Please feel free to correct me if I am wrong. :)  Thanks again for a great channel!

    • Lisa

      actually, nutritional yeast does not naturally have B12, only the fortified kind.

  • Gary Yuen

    Worth noting that pretty much any fortified food is processed and not really a whole food. Better as a supplement.

  • Dada

    what about b12 shots?

  • Stephen Lucker Kelly

    I read this:

    Can you be sure the body will not make enough B12 it’s self? Can you show me science that proves we can’t absorb the B12 in our intestines? Thanks

    • Dan

      I hope you realize that most, if not all, the people sited in that article are not credible sources in either the medical or scientific community. While they may be popular in raw food circles, they practice psufo-science and their ideas border on dangerous. If you want to develop b12 deficiency because you listened to Doug Graham, go ahead.

      • Stephen Lucker Kelly

        Doug Graham has a Ph.D, and is well respected. It’s not pseudo-science. Helps if you know how to spell pseudo. I have read what many people have said about B12, from Dr. McDougall to pretty much every vegan nutritionist and doctor that is well known. And a lot have said that it depends on the person. And most people only get B12 problems in there 50s. When the body starts to break down. So I asked for evidence to show why B12 is not absorbed by the intestines. As for some people it is. Some it isn’t. It depends on the person as far as I am aware. If people take B12 all the time we wont evolve to make our own B12. So do what you think.

  • Tracie

    What about nutritional yeast?

    • beccadoggie10

      Nutritional yeast used to have low levels of Vitamin B-12, but has it been genetically modified (with recombinant DNA) like other sources?

    • Don Forrester MD

      Nutritional yeast can be an acceptable source of Vitamin B12 see the video… As the video implies the amount varies with some nutritional yeast being supplemented with Vit B12 as are other products such as the plant based milks. The easiest and cheapest is to take a tablet once a week see…

  • D’Arcy Cooper

    What about sauerkraut? What is the B12 content of sauerkraut?

    • D’Arcy Cooper

      I never see any mention of sauerkraut in B12 discussions. But sauerkraut is full if bacteria that are known to produce B12. So surely it is an excellent source. And could potentially remove the need for supplements.

  • Fidel Castrati

    Even Dr. Greger admits cyanocobalmin is not THE safest form of b12 for EVERYONE, and that’s the kind included in fortified foods and the cheaper supplements. The safest would be methylcobalamin, adenosylcobalamin & hydroxycobalamin, the first 2 of which are already in the bio-active form. It seems wise to ingest a sublingual version of one of those 3, in case there are any intestinal absorption issues. Can nutritionfacts verify this?

    • Michael Greger M.D.

      Cyanocobalamin is the best source for nearly everyone. It may not be wise to rely on the others since there are less data on appropriate dosing.

  • Timothy Solomon

    “Those are some hard-core vegans” :D

  • Ronald Chavin

    The human brain continues to shrink as it gets older. Vegans tend to have the fastest rates of brain shrinkage because they tend to be deficient in vitamin B12. Even people who eat plenty of meat every day have moderately fast rates of brain shrinkage, although not nearly as fast as vegans. People who swallow 1,000 mcg of vitamin B12 daily from pills have the slowest rates of brain shrinkage:
    CONCLUSION: Even people who eat lots of meat every day should swallow 1,000 mcg of vitamin B12 daily from pills. At present, there is no evidence that swallowing more than 1,000 mcg of vitamin B12 daily will slow the rate of brain shrinkage any better than swallowing exactly 1,000 mcg of vitamin B12 daily, which is a very safe dosage.

  • Gabriel

    I’ve seen the paper of Sheila Callender used in the reference and it does not say that vegetarians where feeding on their stool..

    • Toxins

      I could not find the full text of th article referenced, but the study referencing it does say this “In one of the less appetizing but more brilliant experiments in the field of vitamin b12 metabolism in the 50’s, Sheila Callender (7) in England delineated that human colon bacteria makes large amounts of vitamin B-12. Although the bacterial vitamin B-12 is not absorbed through the colon, it is active for humans. Callendar studied vegan volunteers who had B-12 deficiency disease characterized by classes megaloblastic anemia. She collected 24-h stools, made water extracts of them, and fed the extracts to the patients, thereby curing their vitamin B-12 deficiency.”

  • finkler

    Hi there, in you video you are speaking about getting 47micrograms a day of B12 through eggs, yet, the recommended minimum intake is about 3 micrograms, and an optimal intake would be around 5-15 micrograms.

    Then you speak about the cholesterol of eggs, but you deny the same argument you make for B12 to the cholesterol, namely that the absorbtion rate of the egg’s cholesterol’s very low, at the very least, highly individual.

    • Toxins

      Please continue watching the b12 series, Dr. Greger explains all of the b12 issues throughout them. Also, I know of no evidence showing that we do not absorb the cholesterol in eggs. Can you share some evidence?

  • Julot Julott

    Do we know why absorption of B12 from eggs is very bad compared to others animal products?

  • Hammer

    This is the height of the health living – to start eating one’s own excrement!

  • 7in1

    Would it go down to a place of absorption if hanging up side down making enema at the same time?

  • Andrés Fava

    Sorry, but what do you think about yeast estract? This is false? I tell people that use it as a source of b12, i`m wrong? Thanks!

  • Jane

    What are your thoughts on B12 shots?